The Physiology of Transport Substances in the Blood (Sodium)
By Professor Marcel Uluitu, M.D. Ph.D.
Co-Authored by Diana Popa (Uluitu), M.D.
Department of Microbiology, Immunology and Molecular Genetics
[Editor’s Note: This paper is presented as Part II of a series of chapters from the new book “The Physiology of Transport Substances in the Blood (Sodium)”; subsequent chapters will be featured in upcoming issues of this Journal. This segment features Section II (of three sections) of Chapter Two (of six chapters)]
184.108.40.206. Aminoacid composition
Table no. 7 The composition of amino acids in the plasma protein (gr/100gr of protein) (139)
histidine 3, 5 1, 31 2, 61 3, 12 2, 55
arginine 6, 15 3, 65 6, 97 5, 03 4, 45
aspartic acid 10, 4 7, 44 8, 26 11, 37 9, 05
threonine 5, 0 4, 80 5, 64 3, 75 8, 90
serine 3, 7 2, 51 5, 64 4, 28 11 75
glutamic acid 17, 4 10, 73 19, 20 9, 46 12, 49
Proline 5, 1 2, 37 4, 12 4, 20 7, 90
Glicine 1, 6 0, 82 2, 53 3, 98 4, 47
Alanine - - 5, 63 5, 47 4, 05
Cysteine 0, 70 0, 60 3, 15 - -
Valin 7, 70 2, 82 6, 41 5, 05 9, 42
Methionin 1, 28 0, 65 - 1, 53 0, 90
Isoleucin 1, 70 3, 85 - 2, 02 2, 59
Leucin 11, 90 5, 21 17, 67 8, 21 8, 57
Tirosin 4, 06 1, 99 3, 43 4, 91 6, 75
Phenylalanine 7, 80 3, 02 4, 69 4, 90 4, 79
Tryptophan 0, 19 1, 25 - 1, 66 3, 42
Plasma protein metabolism. Turnover of proteins is variable, according to the fraction considered. Globulins have a slower turnover. Protein synthesis is stimulated by some intermediates (130, 139). Degradation products of prothrombin stimulate its own synthesis. Cytokines have different effects on the well-differentiated hepatocytes with effects on acid phase protein synthesis and on plasminogen, etc.
220.127.116.11. The main plasma proteins.
Albumin is the most significant fraction in point of quantity. Together with prealbumins, it migrates the fastest on the electrophoregram. Plasma content is 4.5-5.5 gm%. It is very soluble in water. It has a small molecule with G.M. = 69,000. It has an important role in colloid-osmosis, adjusting the hydro electrolytic equilibrium, in blood transport processes. Its molecule is spherical or ellipsoidal. It is a polydomenial molecule and has only amino acid residues (Table No. 7). The electrical charge is given by 96 lateral negative groups and a similar number of positive ones. At the physiological pH of the blood - 7.4, it has a large number of negative charges, 12 -15 COOH dissociated protons, histidil which gives more stability. The molecule is surrounded by a layer of water. Electrophoretic mobility in veronal buffer is 6.7 -7.4 x 10/cm/V/sec. The isoelectric point is pH = 4.7. The refoldings are fixed by disulphur bridges, which favor the binding of heavy metals. Albumins are resistant to denaturizing, which is important in the plasma. It is synthesized in the liver. Albumin is distributed between blood and the extra vascular space, having a small molecule. Half of its value in blood helps to maintain volume equilibrium between the two compartments and in transport processes. Synthesis depends on their intake of amino acids, on some hormonal actions (thyroxine, steroid hormones). Synthesis is stimulated by the loss of protein, by the products of their degradation and by the action of cytokines. They provide 75 - 80% of the colloid-osmotic pressure of plasma. They have also a role in maintaining the acid base equilibrium, reservoir of amino acids. They also bind carbon hydrates, hydrophobic compounds as free fatty acids, liposoluble vitamins, steroid hormones. For binding, a pocket of hydrophobic amino acid is formed that has a collar of cationic hydrophilic amino acids. Fatty acids are attached with their lyophilic end to the pocket and with their hydrophilic end to the collar (COO). More than half of serum lipids are transported on albumin even chilom. Serine protease inhibitor (serpine) is a group of glycoprotein in serum with inhibitory action on protease having protective action on the body. They represent about 10% of the total protein levels. The group includes antitrypsin, antichimotrypsin, antithrombin III, protein C inhibitor, macroglobulin. Inhibitory activity is relatively specific. They have no role in the transport of substances through blood.It is synthesized in the liver, macrophages, endothelial. GM = 735,000.
icrons. It binds the biliary salts, acids coloring, drugs (atropine, quinine, pilocarpine, digitalis, etc.). In pathology, hyperalbuminemia is insignificant. Hypoalbuminemia accompanies the nephrotic syndrome, chronic hepatitis, acute and chronic digestive diseases, burns, bleeding, malnutrition, etc.
Table. 8.The% content of sugars in proteins (139).
Protein Hexoze Hexozamin Sialic acid Fucose
prealbumin 1, 1 0, 15 0 0
glycoprotein 15, 0 12, 00 12, 00 1
ceruloplasmin 3, 0 1, 90 2, 00 0, 18
haptoglobin 7, 8 5, 30 5, 20 0, 20
macroglobulin3, 6 2, 30 1, 80 0, 12
12, 0 13, 00 17, 00 0, 60
transferrin 2, 4 1, 60 1, 40 0, 07
fibrinogen 3, 2 1, 00 0, 80 0, 00
2.4. Inorganic compounds of plasma.
18.104.22.168. The structure of water
Figure 3. Water structure (68)
22.214.171.124. Water in the body.
126.96.36.199. Chemistry of sodium
Na 0, 95 3, 58
K 1, 33 3, 31
Cl 1, 81 3, 32
Br 1, 95 3, 30
I 2, 16 3, 79
188.8.131.52. Distribution of sodium.
184.108.40.206. Equilibrium of sodium in the three spaces of the body.
Its distribution in the three spaces and among the components of each space complies with the laws of physical and chemical equilibrium (3, 57) with different functional meanings as follows: Equilibrium between intravascular Na (44) and extra vascular (interstitial) Na and between that the latter and intracellular Na. Within the intravascular space, there is a balance between Na in interaction with blood proteins and chemically active Na. In the extra vascular space (51) with a heterogeneous composition, there is equilibrium of sodium, between the forms of deposit, with Na in the liquid matrix. Na balance between the three spaces through separating membranes is achieved by diffusion (85) together with other substances such as water, K, etc. amino acids, and by active processes with various speeds. Water becomes uniform in the blood and the interstice within 30 seconds while the balancing of Na requires 60 minutes. Interstitial balance and intracellular balance is obtained for radioactive water in 120 minutes, for Nain 24 hours, and for in K in 25 minutes, showing that Na adjusting is independent of that of water (43). These types of general equilibrium are dependent on the balance between intake and elimination of the cation described by a polynomial (222, 223. 227). The total amount of Na in the body is 3500 - 4500 mEq of sodium (80 - 100 gm) (43, 44). It is present in an osmotic inactive form, of which 500 mEq of sodium (11.5 gm) in connective tissue, cartilage and 1.400 - 1900 mEq of sodium (32 - 45 gm) in the bones, skin tissue and adipose tissue. 30% of Na is osmotically active and participates in the tensio-osmo-regulation process. Of the total Na, 2800 to 3000 mEq of sodium, (41 -42 gm / kg) is the amount of exchangeable cation (Ganong and Harper cited by 44). This shows the active exchange between fixed, osmotically inactive Na (35, 57, 56) and Na circulating in the interstitial fluids and blood. This distribution of Na shows that in addition to metabolic, (34) osmotic and rheologic factors, different physical and chemical factors also have a contribution such as the multitude of anionic groups interacting with Na (240)
220.127.116.11. The role of sodium.
18.104.22.168.2. Chemical methods.
(e) nuclear activation
(29, 74, 125, 142, 149, 150): Potentiometry with
ion-selective electrodes measures the plating cell potential versus the
reference potential "0" As a principle, the potential of the active
electrode versus the reference potential is proportional to the concentration
of active chemical species, selected by the ion-selective electrode similar to
the H electrode in pH determinations. The method is used for determination of
electrolytes in whole blood, undiluted plasma and other biological fluids (84).
The ion - selective method produces the value of the active form of ionized Na
and K mM /l, lower than values obtained by flame
photometry, either because of Na binding protein or the formation of ion pairs
(126). The precision of the method increases as the degree of dilution increases
and is maximum for the basic condition: infinite
dilution. The ion-selective electrodes can be used in vivo and in cell cultures
(35) enabling the study of the Na / K during cell function. Anodic voltammetry also uses selective electrodes versus the
reference, mercury electrode.
(f). Chromatographic methods also require preseparation of cationic with various means: electrophoresis, precipitation, ultrafiltration, dialysis. Chromatography was originally used for the separation of organic species and subsequently to metallic ions. Adapting these methods for inorganic analysis was done by amending the two phases, stationary and mobile, simultaneously or successively, as needed (125), for the monovalent and divalent cations. Chromatographic columns are made of glass or metal (aluminum) filled with inorganic or unpolar beds with different additions: tyramine, compounds in the crown for excellent separation of monovalent cations, followed by photometry (150, 179, 200, 201). Stationary phases may be liquid, cellulose, silicagel, polyacrilamide, alumina, alone or in mixtures adsorbent, inorganic ion exchangers (aluminosilicates rich in Na, K, Ca, Sr, Ba exchangeable with cations in the electrolyte solution, hydrated oxydes, etc.) Organic on exchangers: ion exchanging resins with varying degrees of acidity, resins of cationic polymerization, basic resins, chelated, amphotere resin that have incorporated complex agents, or chelating agents with a high capacity of selectivity, electrons exchanger resins, resins with varying degrees of porosity, with polar groups which gives them hygroscopicity, by interacting with ions which alter their Natural hydrophylia Na K Cs Rb Li. The stationary phase can be modified by impregnation with polysaccharide ions: heparin (179 ), dextransulphates, condroitinsulphates with sulphydrilic groups that set cations. Heparin (considerably reduces the retention of anions), biliary acids, etc. The impregnation of the stationary phase with special substances, allows the separation of anions and cations also according to their valence. The chromatographic separation enables one to obtain values comparable to other methods. The eluent can be chosen and prepared so as to allow selective elution also function of the fixed phase, HCl, tartaric acid, etc. Among the methods outlined, the vast majority do not meet the basic condition i.e., to keep intact the structure of the composition of the environment including macromolecules. The methods that use ion-selective electrodes meet these conditions to the largest extent, being also used in vivo. They require special attention for more convenient measurements. I presented the factors affecting the values of the chemically active Na+(231, 232, 233). Plasma Na+ is in interaction with a wide variety of anions and anionic sites on macromolecular compounds and in conformity with the law of multiple equilibrium, the energy intensity variables.
Interactions between plasma components.
From the point of view of 2nd law of thermodynamics, transport occurs if there is a gradient different from "0" of one parameter.
The thermodynamic force generates a stream (94), whose final purpose is the destruction of the gradient. In living systems, however, regeneration of the gradient occurs at the same time with the cancellation of the gradient by means of general biological physical and chemical processes, and by means of metabolic processes. The Natural processes involved in gradient destruction are: diffusion, convection, osmosis, adsorption and absorption, capillarity, etc. The action of mechanical processes and the flow of fluids (blood, lymph) are added to those processes, speeding up the destruction of the gradient.
interaction (L / T) (101)
[L] + [S] => [LS] where [L] = ligand
[S] = site on the transporter: k = association, dissociation constant. The
equation to balance measures the affinity of L for S, which is defined by the
Studies of saturation of the process of interaction, enable the determination of binding parameters (218, 232, 233, 231, 224, 236): the density of binding sites (Bmax) (92). The kinetics of the LT interaction is being investigated on the basis of the law of mass action and of the Michaelis-Menten equation. The binding constant and the number of binding sites (Bmax) are calculated with the Scatchard equation (180):
B / F = Bmax-B / K (180)
The regression curve is right for a single set of
interaction sites on the transporter. Non-linearity indicates the existence of
several other sets of sites.
of L / T interaction.
10: Types of hydrogen bonds (52).
O-H. ....... O - H
22.214.171.124. Van der Waals forces.
126.96.36.199. Electrostatic interactions.
188.8.131.52. Physical forces of adsorbtion-desorbtion.
The compound is formed of the ligand and the aromatic residues of the amino acid side-chains of protein. The ligands are cationic amino groups (68), alkaline metals, etc. The structures involved in the interaction with cations (Table 11) are aromatic amino acids or their residues from protein compositions, phenylalanine, tyrosine, tryptophan, pirolic ring of globular macromolecules (90), acting as a donor of electrons, and provides flexibility in environments with low polarity and favor cationic access to imidazolic level, preferred to form the cation -complex with smaller distances than Van der Waals forces. Cation - interactions are also established with polar and hydrophobic residues (48) between coordinated ligands to a metal cation. These coordinated ligands interact with asparagine, aspartic acid, glutathione, histidine, treonine, valine, (251), with two molecules of water (250), lisine (184). Aromatic rings have a well defined electronic distribution whose result is that cations are arranged perpendicularly on a plane. The study of cation- associations is performed with computational methods, with mass spectroscopy, analysis of solid structures, crystallography, fluorimetry (emission of fluorescence analysis) of aromatic nucleus in interaction with metallic cations (Na, Li) (226). The mechanisms of -cation interactions are multiple. Forces of electrostatic attraction correctly describe the -cation interactions (48) between cation positive charge with quadrupolic momentum of the aromatic ring. Chemically, there are also cation- non-conventional interactions, where the electrostatic attraction is achieved without an input of electrons (184). In some cation- interactions there are phenomena of polarization deducted from the effects of perturbation of the potential of general molecular interaction. The polarization is accompanied also by electrostatic forces and by dispersion-repulsion forces. Molecular interaction through polarization enables the very quick binding of cations to aromatic compounds (42). From the analysis of the fluorescence emission of the solution containing aromatic amino acids and cations (Na, Li) one demonstrated the deactivation levels of radiative energy transition of the orbitals (226) and established that the bases order of anions is
indol phenol benzene
in the interaction Li- when anions are reduced in the presence of a cation (96).
protein groups, electrolytes, free amino acids, aromatic amino acids.
(1) (2) (3) (4) (5) (6) cation -
COOH CH Na Cl aspartic involved tyrosine
OH CHOH K SO glutamic in phenylalanine
CHO CH Ca F histidine quilibrium tryptophan
CO CH Li - lysine multiple histidine
NH CH - - treonină - aspartic
=NH CH - - cystine - asparagine
CONHCH - - arginine - treonine
CORNH - - - - - valine
SH - - - - - lysine
(1) = hydrophilic radicals. (2) = radicals hydrophobia
Chemical activity of plasma electrolytes.
Research of X-ray diffraction (68, 153) showed that
dry NaCl crystals are formed by ion Na and Cl just like in solution. Ions in water can move freely due
to the dielectric constant of water. In a solution containing NaCl and polianions, there is a
free equilibrium between free Na and Na retained around the polyanion
through various interactions. The free fraction is quantitatively less than
that measured by potentiometry or conductometry,
therefore it does not show the results of dissociating theelectrolyte (153), (the vapor pressure, cryoscopic point) which would explain the number of
particles resulting from dissociating them described by an equation of the type
NaCl Na + Cl
because there is no such equation, and also a constant k.
The chemical potentials”” and”” of the solution of NaCl (Debye-Huckel cit.153) are associated with their
concentrations by the equations:
, where c and c are concentrations of Naand Cl.
From this data there results an apparent decrease of the concentration of ions with opposite sign, by the attraction between them, with solvent molecules or anionic sites of proteins, when calculating the concentration, a value defined as " cation activity." Electrostatic forces decrease the free energy in parallel with increasing the concentration of salts and increase the coefficient of activity. The notion of "activity" is used correctly instead of "concentration" for electrolyte solutions, defining the actual capacity of interaction of free reactive forms . The activity of blood cations is an incompletely clarified concept due to the complexity of the environment that changes the free forms of cations. The values reported depend on the method used to determine them: the elimination or modification of proteins or by the accumulation of catabolic acids (121) or in the presence of purified proteins (137) or by methods that preserve the structure and function of macromolecules (228, 231, 232, 233) using competition of polyanion heparin for serotonin, - a method accepted and recommended by Al.Monnier (see facsimile). The results obtained with this method show that in the blood serum collected from different species, the activity is evident only after denaturizing by mechanically stirring the serum. According to this data, in humans and rats (normal) one cannot detect the cationic activity of sodium. This is in interaction with blood proteins (Table 11).
2.7.The transport of some substances in the blood.
A chapter of such an expanse requires a thorough treatment, which is not our intention. The paper only aims to illustrate the problem with some substantial examples in support of the idea of the physiopathologic significance and physiologic mechanisms of transport in the blood of certain substances, thus suggesting the opening of a new chapter of physiology, to explain the fundamental physical-chemical mechanisms at the molecular level.
Ca = 6Ca – Pr / 3 / Pr + Ca.
Binding to plasma proteins depends on their
concentration, environment pH, H antagonizing the binding of Ca .
Oxygen is transported through well studied, understood reaction, on hemoglobin and can be correctly described by the dissociation curve of oxyhemoglobin (78, 99).
Serotonin (219, 220), a biogenic amine derived from tryptophan is involved in the function of the nervous
system as a synaptic mediator. It has importance in carcinoid
pathogenesis. It is completely transported, under normal circumstances,
attached to platelets. In pathological conditions, its transport is perturbed
and 5HT is also present in a
2.7.9. H-ion. Acidic-basic equilibrium.
Metabolic processes going on in tissues generate H+ which affects the blood pH shifting it to the acidic side. Depending on the intensity of metabolic processes, there are differences of pH of the efferent blood of different organs. Difference of pH also exists between different segments of the vascular tree. The pH of arterial blood is 7.4 and that of the venous blood is 7.35. A constant concentration of H is maintained through two main mechanisms.
In the first stage, the physical-chemical processes of
the blood buffer systems come into play for the maintenance of the acidic-basic
balance (68, 78) (Henderson-Haselbach equation).
describing the couples of acid/base buffers. There are four buffer
systems in blood:
In the mechanism of maintaining the blood pH, the most important role belongs to red cells and plasma proteins. Proteins intervene by their lateral and masked amino acid residues. Thus in the acidic environment, proteins accept a greater quantity of protons . At the level of elimination organs, protons are dissociated from the protein and removed. This is the second phase of mechanisms that maintain the blood pH. The concentration of hydrogen depends on age, activity, nictemer, digestion phase, etc.
2.7.10. Circulation of hormones with transporters.
Table. 12. Transporters hormonal blood protein. (221)
Protein transporter MW fluidic fractions number.
HSA ( hormone serum albumin) 69.000 0
CBG (corticosteroid binding globulin=transcortin) 52.000 26
AAG ( -acid glicoprotein )
2. 7.10.1. Growth hormone (GH).
GH secretion is achieved through the nutritional status and the stress of
organisms, of which the most important is the level of cellular proteins.
Malnutrition stimulates by feedback (60.14) the secretion of growth hormone
through hypothalamus with a regulatory loop that includes somatoliberine
and somatostatine. At the hormone receptor level
there occurs the separation of the polypeptide hormone
from its plasma protein transporter. The molecular weight of the receptor is
somewhat smaller than that of the original isolated receptor, the difference
being given by glycosilation. Anomalies of the
complementary DNA encoding for GH receptor are found in children with Laron dwarfism (syndrome of resistance to GH), proving the
biological importance of the receptor.
It increases during slow wave sleep and during the intake of free fatty acids. It also increases during fasting in anorexia nervosa, cirrhosis. It decreases in obesity, the emotional disorders (emotional depression). GH stimulates skeletal growth, the growth of connective tissue, of the muscles, of the viscera. There are two hypotheses concerning GH actions: the first one admits a direct action on cells, the second insists on somatomedinic mechanisms, attributing a special role to IGFI,
They influence protidic and lipidic metabolism and, like insulin, stimulate the transportation of glucose and amino acids into muscles, but by different mechanisms than those of GH (36). They stimulate the formation of the organ and bone matrix, capturing sulphate and thymidine in condrocytes whose growth they stimulate. The somatomedinic hypothesis starts from the observation that the growth of the mitotic cartilage in vivo depends on the presence of GH inactive in vitro. It is known that IGFI and IGFII are components of the serum. IGFII is increased in acromegaly and low in growth hormone deficiency, suggesting that IGFI is the main mediator under the influence of GH, the locally produced IGFO contributes to the stimulatory effects of GH in particular to longitudinal growth.
184.108.40.206. Thyroid hormones.
It carries only T. It has less affinity for the hormone. Carrying 20% of T. TBPA is synthesized in the liver. Albumin and prealbumiNa carrying 10% and 30% T, T. Capacity binding protein is influenced by certain conditions, and especially the TBG. Increased protein decreases the level of T and temporarily increases secretion of hypophysial TSH , therefore the synthesis of T and T At the same time with modifications of binding protein concentrations or their capacity to interact with hormones there occur changes of hormones concentration. Converting T to T is dependent on deiodinase in the pituitary and liver. There are a multitude of(242) conditions in which TBG may modify its ability to bind thyroid hormones. T is deiodinated at T in peripheral tissues: liver, kidney, brain, thyroid. HT level (198) is not influenced by age though the proteins are modified: albumins concentration decreases and there occurs a high concentration of -globulins. TBG synthesis is accompanied by increased blood lipids that inhibit the binding of proteins to T transporter, TBG, TBPA and prealbumins, a process, called "thyroid hormone binding inhibitor = THBI. Thus, T binding decreases in the elderly who have a poor state of nutrition. THBI increases its activity if the TBG and albumins decrease. It therefore lowers the concentration of bound T and increases the free form especially if chronic respiratory, kidney, cardio-vascular diseases are present and accompanied by a decrease in T3 as well.
Adjustment of thyroid function is performed by
classical mechanisms involving the thyroid, hypothalamus, pituitary and
peripheral consuming hormones, with a feedback mechanism. HT complexity of action,
with the associated transport mechanisms, requires in addition to clinical
activity of the thyroid gland the highlighting of quantitative aspects by
determining their concentration and the
investigation of transport mechanisms through several methods:
(4) Measurement of serum T4 and T3.
Dosing of T3 has no meaning, its values are always normal in the
plasma.T4 values (70-150 mM% a) reflect
(6) Analogue methods analogous. An HT antibody is
added and one determines a derivative marked by HT (analog), which binds de -antibody and not the binding protein of T. Competition
between the analogue and the free HT allows determination of free HT.
220.127.116.11. Corticosteroid hormones.
Corticosteroid hormones are somewhat similar
mechanisms of transport (246). The adrenal cortical has three distinct
morphological, enzyme and secreting areas: the glomerular
area secretes mineral corticoids (aldosterone, desoxycorticosteron): the fasciculated
area secreting glucocorticoids (cortisol
and corticosteron): the reticulata,
which secretes sexoid hormones (dehidroepiandosteron,
Their blood levels vary with age, nictemer, the level
of physical activity, etc.. Adrenal cortical hormones are derivatives of
cholesterol (215, 216) with progesterone as their turntable. Adrenal cortical
hormones, as in fact all steroids, are transported in the plasma, most of them
protein-bound (54). A small fraction of bind to circulating red cells and a
lesser part are in a
Hormone %free %albumin bound %bound CBG
The adjustment of cortisol secretion recognizes the general feed back mechanism having as the starting point the concentration of free hormone. In humans, CBG binds up to 25g / gm. As CBG becomes saturated, binding passes on to albumin. The adjustment of mineralocorticoids secretion has a more complex mechanism, involving, in addition to the common stimulus - the concentration of free hormone in blood- the level of extra cellular fluid and of the blood, arterial pressure, Na and K concentration in plasma correlated with the renin-angiotens in the system. The corticosteroids pathology recognizes as a mechanism, their synthesis, concentration and quality of plasma protein transporter, mainly CBG, (80) and finally the relative strength of the tissue toward the hormone, thus lowering their use. Structural changes in quality and reactive protein transporter works by increasing the processes of dissociating the complex CBG-cortisol. CBG activity is low in some types of stress (bacteria shock, fungi, or surgery, burns, operations in the abdomen and thorax, etc.).
Hypoalbuminaemia is also accompanied by a decrease in bound cortisol. These data confirm the importance of binding and transport mechanisms in the pathogenesis of endocrine disorders interesting the glucocorticoids. These processes are difficult to highlight in the case mineral corticoids processes, as binding and dissociation are fast and the hormone is bound for less time. Adrenal sexed hormones have mechanisms of transport and binding similar to those of gonadal hormones. They are bound by SSBG glycoprotein (tb.12) and albumin for which they have lower affinity.
18.104.22.168. Gonadal hormones.
Testosterone circulates in a bound state, bound 100%
to a β globulin, TEBG, having low capacity and to SHGB, together with dihydrotestosterone and androstendiol.
Synthesis is driven by oestrogenization. TEBG is
synthesized in the liver. It is generally admitted that senescence of the
endocrine system refers to the ability and rhythm of glandular secretion, to
the transport and metabolism of hormones in regulating the activity of systems
and hormonal receptor sensitivity (88). Another part of testosterone (37%)
circulates in a bound state, related to albumin, and a significant part is
carried on CBG. Only 2% moves in a
Beyond the age of 60, the plasma free fraction decreases and the albumin-bound fraction increases , due to the growth of increase its affinity for steroid. There is also an increase of affinity for SHBG, whose synthesis is stimulated by oestrogenization in the elderly.Progesteron however, induces a decrease of testosterone bound fraction. The metabolism occurs in the liver. The specific action of testosterone is to stimulate spermatogenesis.The non-specific effects refer to secondary sexual characteristics and metabolic effects. Secretion adjustment is achieved by feed back with a hypothalamus and hypophysis link acting through LH and FSH gonadoliberines and goNadotrophins.
Female gonadal hormones are secreted, as other steroids, by glands of coelomic origin, the ovary which has three anatomic functional compartments: follicular, secreting mainly, oestrogen hormones (oestradiol and oestron); progestational, composed of lutein cells and thecal cells which have progesterone as a specific product, and stromal, made up of stromal cells secreting androgens (androstendion, dehidroepiandrosteron, etc.).. The ways of synthesing them are the same as those of all steroids (215, 216).
Oestradiol is transported bound to SHGB, albumin, and the CBG. Together with oestrone, it binds, in a proportion of 98 - 99% to particular sites, with strong interactions, and thus it regulates its activity also owing to the multiple possibilities of the ovary to synthesize oestrogen hormones. Due to this fact, their concentration is not relevant, and, in addition , it intervenes in the response capacity of tissues. Ovarian hormones circulate mostly bound to albumin and globulin transporters. SHBG has a small binding ability, but has high affinity. Oestradiol, progesterone and oestron bind to a lesser extent. In the elderly, cirrhosis and hypothyroidism patients, SHBG increases in parallel with the oestrogenisation of the person. SHBG concentration in plasma is 2-3 mg ‰. It is synthesized in the liver. Synthesis is stimulated by oestrogen and inhibited by androgen. Progestern and 17-hydroxyprogesteron are transported also on CBG. Albumin has little affinity for these hormones, but their binding capacity is greater than that of THBG. Ovarian hormones are distributed among various adipose tissue, digestive tissue, target organs: endometrium, myometer, brain, mammary tissue, kidney). The free forms of ovarian hormones have a catamenial rhythm. They are eliminated by the kidneys and in bile. Their action is specific on the target organ and unspecific on metabolism general. The transport of progesterone uses the same transporter as oestrogens (173). Its synthesis increases during pregnancy. Progesterone has an oestrus cycle. Metabolism takes place in the target organs as well. Its main activity is to differentiate cells of progestogen organs.
[The remainder of Chapter 2 will be featured in the upcoming November-December issue of this Journal.]
Professor Marcel Uluitu, M.D. Ph.D. began his
scientific activity in Physiology in 1953 at the
Professor Uluitu has also investigated cerebral tissue excitability, studying the structure modification of the protein macromolecules, and the physiological and pathopysiological processes in which are involved Sodium and Lithium. He implemented an original method for physical and chemical processes which involve the chemic active sodium, in normal processes and in the cerebral excitability dysfunctions, in human and in experimental model (animal). These results of this work gave him the chance to outline the chapter herein relating to the physiology of substances transport in the blood. This is based on the physical and chemical interaction between blood components.
His papers are included in the
collections of the U.S. National Library of Medicine and the U.S. National
Institute of Health. He is a member of the
Dr. Diana Popa (Uluitu) is a
researcher in the Department of Microbiology, Immunology and Molecular Genetics
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