Modulatory effects of unsaturated fatty acids on the binding of glucocorticoids to rat liver glucocorticoid receptors

Binding of the synthetic glucocorticoid dexamethasone to the rat liver cytosol glucocorticoid receptor was inhibited by physiological concentrations of nonesterified fatty acids as a function of increasing dose, degree of unsaturation, and chain length of the fatty acid. Polyunsaturated fatty acids were the most potent inhibitors. Scatchard analysis and Line-weaver-Burk plots of the binding data revealed that both the association constants and number of binding sites decreased and that polyunsaturated fatty acids inhibition was of a mixed non-competitive type. The dissociation rate constant of [3H]dexamethasone from glucocorticoid receptors was increased by up to 10 times in the presence of docosahexaenoic acid, whereas a competitive inhibitor like the glucocorticoid antagonist RU 38486 had no effect. Moreover, sucrose density gradient analysis showed that docosahexaenoic acid inhibited the binding of [3H] dexamethasone to both the 8.8S and 4S forms. The results strongly suggest that unsaturated fatty acids are interacting at a site on the receptor different from the hormone binding site and the heat shock protein and that by binding to a second site unsaturated fatty acids greatly change the conformation of the hormone binding site to reduce its affinity for the hormone, either partially or completely depending on the concentration and the class of the fatty acid.

A senescence up-regulated protein: the rat thyroxine-binding globulin (TBG)

Thyroxine-binding globulin (TBG), the major carrier of thyroid hormones in human serum, was thought to be absent in most species, including rodents. We demonstrated recently that in fact the rat possesses a TBG gene, virtually non-expressed in young adults, but actively transcribed during post-natal development. We now find that the TBG gene is also increasingly re-expressed during senescence. Evidence is presented suggesting that physiologically decreased thyroid hormone levels, characteristic of neonates and of ageing rats, might constitute a common factor inducing up-regulation of TBG in both developmental and ageing processes. Rat TBG is to our knowledge the first biochemical 'positive' (i.e. increasing) marker of non-pathological senescence, expressed at both biosynthetic and bloodstream levels.

ATP-dependent uptake of 5-hydroxytryptamine by secretory granules isolated from thyroid parafollicular cells

The current study was done to test the hypotheses that parafollicular granules contain a vacuolar ATPase (V-ATPase) similar to that found in chromaffin granules, that the transport of H+ into granules mediated by this enzyme drives the granular uptake of 5-hydroxytryptamine (5-HT, serotonin), and that secretagogues stimulate both the acidification of parafollicular granules and their ability to take up 5-HT by opening an anion channel in the granular membrane. Our studies indicate that parafollicular granules contain a V-ATPase that is antigenically similar to that of the V-ATPase of adrenal chromaffin granules; however, the parafollicular granular membrane differs from that of chromaffin granules in permeability to Cl- and K+. The membranes of granules derived from resting parafollicular cells appear to be relatively impermeable to Cl- but permeable to K+. Parafollicular granules (and ghosts derived from them) manifest ATP-dependent transmembrane transport of 5-HT. This transport is more dependent on the pH difference (delta pH) than on the membrane potential component of the proton electrochemical gradient across the granular membrane. Transport of 5-HT is thus inhibited more by exposure of parafollicular granules to agents, such as nigericin, that collapse delta pH than by those, such as valinomycin, that decrease transmembrane difference in potential. ATP-dependent uptake of 5-HT by granules isolated from secretagogue-stimulated parafollicular cells is greater than that into granules isolated from unstimulated cells. Since secretagogues open a Cl- channel in parafollicular granule membranes, which enhances acidification of the granules, the facilitation of 5-HT uptake by secretagogues is probably due to an increase in delta pH.

Endotoxin induced changes in serum estrogen in male rats: influence of testicular maturation

The influence of acute endotoxin (Endo) administration on adrenal and testicular serum hormones, corticosterone (B), progesterone (P4), 17 alpha OH progesterone (17 alpha OH P4), androstenedione (delta 4), testosterone (T), estrone (E1) and estradiol (E2) was studied in male rats aged 8, 12 and 15 weeks. The present study confirms that the concentrations of circulating steroid hormones in male rats vary with age, and indicate that the adrenal glands mature before the testes. The steroid response to Endo is age-dependent. B, P4, 17 alpha OH P4 was increased and T decreased in all animals. But, there was a very significant increase in estrogens (E1 and E2) and a decrease in delta 4 only in male rats aged 12 weeks and over. The lack of an estrogen response to Endo injection in 8 week-old rats may indicate that the reduced sensitivity (refractory period) to Endo (which has been reported to last until 21 days of age) continues longer. The reduced sensitivity to Endo which occurs in young rats could be due in part to the absence of adrenal-testicular cooperation as a result of partial testicular immaturity.

Sex steroids, glucocorticoids, stress and autoimmunity

Interest in the field of neuroimmunoendocrinology is in full expansion. With regard to this, steroid influence on the immune system, in particular sex steroids and glucocorticoids, has been known for a long time. Sex steroids are part of the mechanism underlying the immune sexual dimorphism, as particularly emphasized in autoimmune diseases. Immunosuppressive and anti-inflammatory effects of glucocorticoids are now considered a physiological negative feedback loop to cytokines produced during an immune and/or inflammatory response. Psychosocial factors may play a role in the development of immunologically-mediated diseases, e.g. autoimmune diseases. The nonobese diabetic (NOD) mouse, that develops an immunologically-mediated insulin-dependent diabetes mellitus (IDDM) is an interesting model to study the role of endogenous steroids. Insulitis is present in both sexes, but diabetes has a strong preponderance in females. Hormonal alteration, such as castration, modulates the incidence of diabetes, whereas environmental factors, such as stress, accelerate the disease. In the present paper, we have reviewed the role of gender, sex steroid hormones, stress and glucocorticoids in autoimmunity as well as analyzed their different levels of actions and interrelationships, focusing particular attention on the immunologically-mediated IDDM of the NOD mouse.

Immunological quantitation of rat and mouse thyroxine-binding globulins. Ontogenesis and sex-dependence of the circulating levels of the thyroxine-binding globulins

We describe the preparation of monospecific antisera against a thyroxine-binding globulin partially purified from immature rat sera by affinity chromatography on thyroxine-Sepharose. The antisera are used for the rocket immunoelectrophoresis assay of rat thyroxine-binding globulin and also, owing to their partial cross-reactivity with mouse thyroxine-binding globulin, for the quantitation of this serum binding protein in the mouse. The thyroxine-binding globulin is measured in developing rats and in sexually mature male and female rats and mice. The results of the ontogenetic study confirm the postnatal surge of serum thyroxine-binding globulin levels, formerly demonstrated with binding techniques. They allow further to define the correlations, dependent on age, of the immunoquantitated thyroxine-binding globulin and transthyretin levels with the abilities of the sera to bind thyroxine. In sexually mature rats and mice we demonstrate an opposite sex-dependence of thyroxine-binding globulin levels, characterized by increased levels of the protein in the female rats versus increased levels of the protein in the male mice. This is the first report of immunological quantitation of rat and mouse thyroxine-binding globulins.

Multiple signal transduction mechanisms leading to the secretion of 5-hydroxytryptamine by MTC cells, a neurectodermally derived cell line

Parafollicular (PF) cells of the thyroid gland are neural crest derivatives. These cells remain plastic even in adult animals and can be induced to exhibit neural properties when exposed to NGF in vitro. A human cell line derived from PF cells, medullary thyroid carcinoma (MTC), has previously been shown to synthesize and store 5-HT, a serotonin-binding protein (SBP), and several neuropeptides; moreover, when grown in impoverished media, MTC cells display neural properties. The purpose of the current study was to utilize MTC cells as a neurally relevant model system to investigate factors involved in mediating 5-HT secretion. Electron microscopic immunocytochemistry revealed that secretory vesicles of MTC cells costore immunoreactive 5-HT with SBP and calcitonin. The cAMP derivative, N6-2'-O-dibutyryl-adenosine 3',5'-cyclic monophosphate (dibutyryl-cAMP; 1.0 mM) increased the concentration of 5-HT in MTC cells and almost doubled the rate of synthesis of 5-HT from L-tryptophan. Dibutyryl-cAMP also significantly increased the secretion of 5-HT. Cycloheximide (20 micrograms/ml) and anisomycin (20 microM) inhibited the dibutyryl-cAMP-induced increase of 5-HT release, suggesting that this action of dibutyryl-cAMP requires protein synthesis. Cholera toxin (1.0 microgram/ml) and forskolin (0.05 mM) in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (1.0 mM) both increased 5-HT biosynthesis and secretion. Attempts were made to identify a ligand that stimulates cAMP-mediated secretion of 5-HT. Both thyroid-stimulating hormone (TSH: 50 mU/ml) and elevated [Ca2+]e (7.0 mM), each of which acts as a secretogogue for PF cells, stimulated the secretion of 5-HT. The effect of TSH was Ca2(+)-dependent. Immunocytochemistry with monoclonal antibodies to the TSH receptor confirmed that these receptors are present on MTC cells. Neither TSH nor elevated [Ca2+]e elevated cAMP levels. Measurements of Fura-2 fluorescence, however, indicated that both TSH and elevated [Ca2+]e increased cytosolic calcium ([Ca2+]i), as did elevation of [K+]e. It is concluded that exocytosis can be triggered in MTC cells by multiple signal transduction mechanisms. Either cAMP or elevated [Ca2+]i can stimulate secretion; however, a secretogogue that increases cAMP has yet to be identified.

Characterization of a major development-regulated serum thyroxine-binding globulin in the euthyroid mouse

We confirm our finding of a major development-regulated thyroxine-binding globulin (TBG) in the serum of the euthyroid mouse and investigate a number of its binding, structural and regulatory properties. Between 16 days foetal and 60 days postnatal life, the thyroxine (T4)- and tri-iodothyronine (T3)-binding activities of the sera show a striking ontogenic pattern: the binding is 2-3 times higher in foetuses than in mothers, then further increases after birth, reaching between 3 and 5 days maximum values which are 7-8 times higher than the adult ones. This pattern is not correlated with the ontogenesis of the acknowledged specific (transthyretin, TTR) and non-specific (albumin, alpha 1-foetoprotein) thyroid-hormone carriers of the mouse sera. PAGE studies demonstrate that the protein responsible for the elevated binding of the perinatal period is an alpha 1-globulin, with a migration similar to that of human and rat TBGs. Scatchard analysis is consistent with the notions that the T4-binding sites of TBG have high association constants, about two orders of magnitude above the T4 sites of TTR (10(9) M-1 as against 10(7) M-1) and low capacities (37 and 4 nmol/g of serum proteins in pups and adults respectively). Isoelectric focusing (i.e.f.) demonstrates that mouse TBG is a microheterogeneous protein separable, as a function of the pH gradient, in up to 10-12 isoforms, Marked shifts of the relative abundance of isoforms in the course of development are evidenced. The modulation of the TBG binding activity by non-esterified fatty acids (NEFA) and the control of its synthesis by the thyroid status are also reported. Mono- and poly-unsaturated NEFAs are strong inhibitors of the TBG, although they affect TTR less readily. On the other hand, the biosynthesis and/or secretion of TBG, but not of TTR, is under thyroid-hormone control, experimental hypothyroidism inducing a marked increase of the serum TBG. The TBG of mouse behaves as a highly significant parameter of development, pointing to a likely important function of the protein in the process of maturation. Our finding of major TBGs in both euthyroid rats and mice suggests that TBG is more widely spread than was thought until now, but difficult to detect in certain species outside definite maturation stages.

Distribution of laminin in the murine pituitary

The distribution and cellular localization of the glycoprotein laminin were investigated by light and electron microscopic immunocytochemistry in the adult murine pituitary gland. Immunoblots confirmed that laminin was the only protein in the pituitary gland of the adult male mouse to react with antilaminin serum. Laminin immunoreactivity was demonstrated at the light microscopic level simultaneously with that of beta-follicle stimulating hormone (beta-FSH) and beta-luteinizing hormone (beta-LH). In addition to its distribution is basal laminae, laminin immunoreactivity was coincidently expressed in gonadotrophs with the immunoreactivities of beta-FSH and beta-LH. Electron microscopic immunocytochemistry was employed on aldehyde-fixed sections embedded in L.R. White. Sites of binding of primary antisera to laminin were identified with affinity-purified secondary antisera directly coupled to 20 nm particles of colloidal gold. Three antisera recognizing laminin were compared and found to result in an identical pattern of immunoreactivity. Laminin was found extracellularly only in formed basal laminae in all three lobes of the pituitary and was not found in extracellular matrices of connective tissue. Laminin immunoreactivity was also found intracellularly in gonadotrophs but in none of the other endocrine or non-endocrine cells of the anterior lobe. Within gonadotrophs, only secretory granules were labeled. The majority, but not all, secretory granules were labeled in each of the gonadotrophs examined, and the proportion of granules labeled with laminin could not be increased by doubling the concentration of anti-laminin serum. Laminin immunoreactivity segregated with the subset of secretory granules containing beta-FSH. In contrast, laminin immunoreactivity was absent in the smaller subset of secretory granules that contain serotonin.(ABSTRACT TRUNCATED AT 250 WORDS)

The hepatic biosynthesis of rat thyroxine binding globulin (TBG): demonstration, ontogenesis, and up-regulation in experimental hypothyroidism

Using a human thyroxine binding globulin (TBG) cDNA probe, we demonstrate that rat liver contains two TBG mRNA species of different length, consisting of about 1.8 Kb and 2.4 Kb respectively. Slot blot analysis of the hepatic mRNAs from rats of different age reveals a fair correlation between the developmental trend of the messengers and that of the TBG circulating levels. Finally Northern blot and slot studies demonstrate that the increase of serum TBG induced in adults by thyroidectomy actually reflects an enhanced hepatic biosynthesis of the protein.

Effect of adrenalectomy at different pregnancy stages on maternal and fetal serum corticosteroid binding globulin and corticosterone in the rat

The response of pregnant rat corticosteroid binding globulin to maternal adrenalectomy was studied as a function of the stage of pregnancy. Non-pregnant or pregnant rats were deprived of their adrenal glands during 4 days. In non-pregnant animals, adrenalectomy led to undetectable corticosterone levels and to the doubling of corticosteroid binding globulin. In pregnant rats adrenalectomized at 12 days and studied at 16 days, the serum corticosterone was likewise undetectable and the corticosteroid binding globulin was doubled as compared with pregnant rats of the corresponding age. In contrast, adrenalectomy from day 14 to 18 or from day 16 to 20 did not deplete the maternal serum corticosterone and the corticosteroid binding globulin remained unchanged. Under these conditions neither fetal corticosteroid binding globulin nor fetal corticosterone were modified. However, when the pregnant rats adrenalectomized from day 16 to 20 also received an injection of 30 mg of metyrapone on days 19 and 20 in order to inhibit fetal adrenal secretion, the maternal response was again a depletion of serum corticosterone together with an increase in corticosteroid binding globulin. Under these conditions, the fetus also reacted by a fall of corticosterone and a rise of corticosteroid binding globulin. Our results suggest that the maternal response of corticosteroid binding globulin to adrenalectomy depends on the pregnancy stage inasmuch as it may be influenced by a supply of corticosterone from the fetus during late pregnancy. Moreover, they show that in this late period, fetal corticosteroid binding globulin is regulated independently.

Thyroxine-binding globulin and thyroxine-binding prealbumin in hypothyroid and hyperthyroid developing rats

We present evidence based on equilibrium and non-equilibrium binding studies, as well as on immunological techniques, that of the two rat specific thyroid-hormone-binding proteins, i.e., thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA), TBG but not TBPA is regulated by the thyroid hormones (TH). Hypothyroidism, induced from the day of birth by daily treatment with propylthiouracil (PTU-rats), leads to dramatic and sustained increases of the TH-binding abilities of the sera measured at equilibrium, whereas hyperthyroidism, induced by treatment with thyroxine (T4-rats), leads to the decrease of these abilities. Polyacrylamide gel electrophoresis and isoelectrofocalisation of radioiodinated T4-labelled sera, together with immunoassay of TBPA, demonstrate that both effects are due to TBG, the levels of which rise in PTU-rats and decline in T4-rats, while TBPA levels do not respond to either depletion or excess of the thyroid hormones. TBG rather than TBPA appears as the key thyroid-hormone-binding protein of the rat, inasmuch as it alone expresses a regulatory function of the thyroid hormones at protein synthesis level.

Conformational changes in rodent and human alpha-fetoprotein: influence of fatty acids

Binding, spectral and immunological studies were performed to demonstrate the conformational changes in rodent and human alpha-fetoprotein (AFP) induced by a free fatty acid environment. Scatchard analysis of estradiol (E2) binding to purified rat AFP indicated that unsaturated fatty acids changed the number of binding E2 sites and the apparent E2 equilibrium dissociation constant which varied non-linearly with docosahexaenoic acid concentration. UV spectral analysis of rodent and human AFPs showed that the absorbance minimum of AFP incubated with unsaturated fatty acid (L-AFP) was red-shifted, broadened and less pronounced than that of purified native AFP (N-AFP). Immunochemical studies with specific polyclonal antibodies to purified rodent and human AFPs (N-AFP antibodies) showed that these proteins lost immunoreactivity after incubation with unsaturated fatty acid. N-AFP antibodies recognized fewer epitopes on L-AFP than on N-AFP, whatever the species. Specific anti-rat L-AFP antibodies were used to demonstrate specific epitopes on rat L-AFP. Rat L-AFP antibodies did not recognize rat N-AFP. Saturated fatty acids were without effect on the binding, spectral and immunological properties of rodent and human AFPs. RIA or ELISA values for human AFP from fetal serum, hepatoma serum, and cord serum, were reduced 80, 50 and 5%, respectively, by unsaturated fatty acids. This decrease correlated with the relative percentage of polyunsaturated fatty acid in each biological fluid. Such results indicate that an unsaturated fatty acid environment induces conformational changes in AFP which may modulate the endocrine and immune functions of this protein.

The physicochemical and biological properties of alpha-fetoprotein depend of its ligand environment

The majority of studies have concentrated on the endocrine and immunological roles of alpha-fetoprotein (AFP). These studies have been strongly orientated and sustained by research showing that rat and mouse AFPs competitively bind estrogen and non-esterified fatty acids. AFPs of other species, such as humans, are not estrogenophilic but all those studied to date bind NEFAs tightly. Endogenous ligands can greatly influence the conformation of the protein and consequently its biological activity. AFP may have three possible mechanisms of action: a) Murine AFP may be a modulatory element of estrogen expression which determines, under the control of NEFAs the concentration of the active free steroid. b) The protein could be transformed by bound ligands, so enhancing or inhibiting its binding to a target cell receptor, and consequently modifying its biological activity. AFP per se, can be the regulatory element. c) AFPs of all species can work as fatty acid binding proteins and modulate the availability of free NEFAs (not bound to protein). These free NEFAs can, in turn, act positively or negatively on various proteins involved in the pathways of the transfer of the steroid and peptide informations leading to cell multiplication or differentiation.

Human medullary thyroid carcinoma: characterization of the serotonergic and neuronal properties of a neurectodermally derived cell line

Parafollicular (PF) cells have been found to be a good model system for the study of serotonergic cellular mechanisms relevant to neurons. PF cells are derived from the same region of the neural crest that gives rise to the neurons of the gut and are capable of extending neurofilament-bearing neuritic processes. PF cells also synthesize 5-hydroxytryptamine (5-HT) and costore 5-HT in the same vesicles as the specific 5-HT-binding protein, 45 kDa SBP. A hypothesis has been advanced that PF cells and enteric neurons share a common developmental precursor. The present investigation was undertaken in order to determine whether a human medullary thyroid carcinoma (MTC) cell line, which is derived from PF cells, sufficiently mimics PF cells that it can be substituted for them in investigations of serotonergic cellular biology. In contrast to PF cells, MTC cells can be propagated in vitro to provide adequate amounts of material for biochemical studies. MTC cells were found to contain neuropeptides, including calcitonin, calcitonin gene-related peptide, and somatostatin, which have also been reported to be present in PF cells and enteric neurons. MTC cells also were observed to store endogenous 5-HT, to be able to synthesize 3H-5-HT from 3H-L-tryptophan, and to take up 3H-5-HT from the ambient medium by a carrier-mediated mechanism very similar to that of serotonergic neurons. In addition, the longterm accumulation of 3H-5-HT in MTC cells was antagonized by reserpine, suggesting that the cells contain 5-HT storage vesicles that, like the synaptic vesicles of serotonergic neurons, are characterized by a reserpine-sensitive transporter of biogenic amines. MTC cells also contain type A, but not type B, monoamine oxidase. Finally, MTC cells were found to contain both 45 and 56 kDa SBP. MTC cells thus retain a great many of the properties of PF cells, and, like PF cells, they are serotonergic cells with characteristics similar to serotonergic neurons. Substantial differences were found in the content of immunoreactive 5-HT and neuropeptides in individual MTC cells. Moreover, the release of newly synthesized 5-HT to the medium exceeded the ability of the cells to store the amine. Studies of the ultrastructure of the MTC cells revealed a limited and highly variable number of secretory granules, probably accounting for their limited 5-HT storage capacity and for the heterogeneity of immunostaining with antisera to 5-HT or neuropeptides.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding activities of thyroxine binding globulin versus thyroxine binding prealbumin in rat sera: differential modulation by thyroid hormone ligands, oleic acid and pharmacological drugs

We use gel equilibration and electrophoretic techniques to compare the binding properties of thyroxine binding globulin and thyroxine binding prealbumin in rat sera. The evidence indicates that TBG bears the serum lowest capacity highest affinity sites for thyroxine (T4) and triiodothyronine (T3) (Ka1 greater than or equal to 10(9) M-1) as well as weaker saturable T3 sites (Ka2 approximately 10(8) M-1). TBPA bears for T4 only Ka2 approximately 10(8) M-1 sites and for T3 only Ka approximately 10(6) M-1 sites. Consistent with these parameters are the specific responses of TBG and TBPA binding activities to varying serum concentrations of T4, T3, oleic acid, the drugs diphenylhydantoin or salicylate. The primary attack of these compounds is aimed at TBG. Small T4, oleate or DPH doses chase the TBG-bound T4 to TBPA, high doses of T4 or oleate but not of DPH inhibiting the T4 binding to both proteins. In the T3-serum interactions, all tested compounds displace the TBG-bound hormone without chasing it to TBPA. The high reactivity of TBG sites designates the protein as crucially involved in modulating the free vs bound serum levels of T4 and T3 against physiological or pathological variations of binding competitors.

The microheterogeneity of rat TBG

Isoelectric focusing (IEF) of native sera from immature or adult rats and of purified or partially purified rat serum thyroid hormone-binding proteins, demonstrates that rat TBG is a microheterogeneous protein. Autoradiography and radioactivity scans of the IEF plates show that it consists of at least four main isoforms, with bands at pH 4.35, 4.45, 4.5 and 4.55. This pattern is remarkably similar to that reported for human TBG. This is the first demonstration of the polymorphism of this recently discovered major binding protein of the rat.

Thyrotropin induces the acidification of the secretory granules of parafollicular cells by increasing the chloride conductance of the granular membrane

Secretory granules of sheep thyroid parafollicular cells contain serotonin, a serotonin-binding protein, and calcitonin. Parafollicular cells, isolated by affinity chromatography, were found to secrete serotonin when activated by thyrotropin (TSH) or elevated [Ca2+]e. TSH also induced a rise in [Ca2+]i. We studied the effect of these secretogogues on the pH difference (delta pH) across the membranes of the secretory granules of isolated parafollicular cells. The trapping of the weak bases, acridine orange or 3-(2,4 dinitro anilino)-3'-amino-N-methyl dipropylamine (DAMP), within the granules was used to evaluate delta pH. In contrast to lysosomes, which served as an internal control, the secretory granules of resting parafollicular cells displayed a limited and variable ability to trap either acridine orange or 3-(2,4 dinitro anilino)-3'-amino-N-methyl dipropylamine; however, when parafollicular cells were stimulated with TSH or elevated [Ca2+]e, the granules acidified. Weak base trapping was also used to evaluate the ATP-driven H+ translocation into isolated parafollicular granules. The isolated parafollicular granules did not acidify in response to addition of ATP unless their transmembrane potential was collapsed by the K+ ionophore, valinomycin. Secretory granules isolated from TSH-treated parafollicular cells had a high chloride conductance than did granules isolated similarly from untreated cells. Furthermore, ATP-driven H+ translocation into parafollicular granules isolated from TSH-stimulated parafollicular cells occurred even in the absence of valinomycin. These results demonstrate that secretogogues can regulate the internal pH of the serotonin-storing secretory granules of parafollicular cells by opening a chloride channel associated with the granule membrane. This is the first demonstration that the pH of secretory vesicles may be modified by altering the conductance of a counterion for the H+ translocating ATPase.

Selective changes in binding and immunological properties of human corticosteroid binding globulin by free fatty acids

The steroid hormones, progesterone (P4) and cortisol (F), have different biological activities but are both bound to human corticosteroid binding globulin (CBG) with similar affinity. This study examines the effect of physiological concentrations of FFA on the binding of these steroids to purified CBG and to the serum of pregnant women. It also analyzes the influence of the FFA environment on the immunological behavior of CBG. Unsaturated fatty acids (UFA) had a dose-dependent inhibitory effect (P less than 0.001) on steroid binding to CBG which was offset by saturated fatty acid-induced potentiation of binding (P less than 0.01) when both were present with CBG. UFAs inhibited P4 binding more than F binding. Comparable results were obtained with pregnant serum or with pure CBG. UFAs seemed able, depending on their concentration, to promote different molecular states of CBG, some with enhanced F binding and significantly reduced P4 binding, and others in which both P4 and F binding was markedly reduced. Scatchard analysis of steroid binding to purified CBG indicated that the UFAs influenced the association constant (Ka) and the number of binding sites (n) for F and P4 binding differently. Low concentrations (less than 16 microM) of arachidonic acid (C20:4) slightly potentiated F binding, with no change in Ka and a 1.6-fold increase in n; this concentration of C20:4 reduced n for P4 binding by 40% and did not affect Ka. Higher C20:4 concentrations (greater than 32 microM), reduced the Ka for F binding but did not apparently change n; for P4 binding, Ka was sharply reduced and n increased. The apparent equilibrium dissociation constant (Kd) for both F and P4 binding varied nonlinearly and differently with increasing C20:4 concentration. Immunoelectrophoresis and immunoautoradiography showed a reduction, or loss, of CBG immunoreactivity in the presence of UFA. The extent of these changes varied with the concentration and class of the UFA. These results indicate that FFA induce conformational changes in CBG which may modulate its activity and so influence the role of this protein in both the endocrine and immune systems.

Abnormal free fatty acids and cortisol concentrations in the serum of AIDS patients

The serum free fatty acid (FFA), cortisol and urinary creatinine, 17-hydzoxycorticosteroid and 17-oxosteroid concentrations of acquired immunedeficiency syndrome (AIDS-I: beginning and AIDS-II: end phase) and AIDS-related complex (ARC) patients were determined. Both groups were compared to a control group (healthy men). ARC and AIDS-I patients. The ratios of stearic (C18:0) to oleic (C18:1) acid were 75%, P less than 0.01 (ARC) and 45%, P less than 0.05 (AIDS-I) greater than normal, due to a decrease in the relative percentage of monounsaturated fatty acids by 25%, P less than 0.001 (ARC) and 20%, P less than 0.01 (AIDS-I). In contrast, the relative percentage of polyunsaturated fatty acids was 85% greater than normal (P less than 0.001) in ARC and 100% greater than normal (P less than 0.001) in AIDS-I patients. Total FFA levels did not differ from controls. Serum cortisol levels were 35% (P less than 0.01) above normal in ARC and 60% (P less than 0.001) above normal in AIDS-I patients. Urinary 17-hydroxycorticosteroids and 17-oxosteroids were very low (2-3-fold lower than normal values, P less than 0.001) in both groups of patients. Urinary creatinine did not differ from controls. In AIDS-II patients the total FFA concentration was below normal 35% (P less than 0.01) and the stearic/oleic acid ratio was 50% above normal (P less than 0.05). The relative percentages of monounsaturated and polyunsaturated fatty acids in this group were similar to those of controls. Serum cortisol concentrations were significantly higher, 50% (P less than 0.001), but the urinary 17-hydroxycorticosteroids and 17-oxosteroids were 2-fold lower (P less than 0.001) than those of controls. Urinary creatinine did not differ from controls. These significant differences from normal may be implicated in the pathophysiology of AIDS and could represent not only a good index of diagnosis and prognosis, but also indicate new therapeutic approach to the disease.

Ultrastructural immunocytochemical studies of the localization and distribution of somatostatin, calcitonin, calcitonin gene-related peptide, and substance P in the bat thyroid follicle

Electron microscope immunocytochemistry was used to determine the intracellular localization and distribution among follicular elements of four peptides: calcitonin, somatostatin, calcitonin gene-related peptide (CGRP), and substance P in the thyroid glands of bats captured in the prehibernation phase of their annual life cycle. Previous studies have shown that this period of the hibernation-activity cycle is characterized by the accumulation and storage of secretory granules in parafollicular cells. Sites of binding of primary antisera to each of the four peptides were identified by means of affinity-purified secondary antisera directly coupled to colloidal gold particles. Calcitonin and somatostatin immunoreactivities were found in all parafollicular cells examined and in every secretory granule within these cells. CGRP was also found in all parafollicular cells examined (n = 75) but only in about half of their secretory granules. In contrast to these peptides, substance P immunoreactivity was not found in any parafollicular cells, but was localized exclusively in nerve endings within the basement membrane of the follicle.