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H Coirini

Publications and source records attributed to H Coirini.

49 records · Page 3Linked to original sources
PubMed1987

Functions and dysfunctions of receptors for adrenal corticoids in the central nervous system.

Glucocorticoids (GC) have several known effects on the function of the nervous system, and GC receptors have been identified in regions responding to hormonal action. In the spinal cord, GC receptors have been characterized in vitro, which share several biochemical properties in common with receptors in better studied areas such as the hippocampus. Moreover, enzymes which are induced by GC in the hippocampus, such as glycerolphosphate dehydrogenase and ornithine decarboxylase, are also under specific GC control in the spinal cord. Yet GC receptors in the latter tissue divert from those in hippocampus during some in vivo as well as in vitro studies. In vivo, uptake of [3H]corticosterone by purified cell nuclei was 5-8-fold higher in the hippocampus as compared to the cord. In vitro, a higher percentage of GC receptors previously transformed by heating, showed affinity towards DNA-cellulose in the spinal cord than in the hippocampus. The enzyme RNAse A effectively increased receptor binding to DNA-cellulose in hippocampus, whereas the cord was insensitive to its action. These results suggest that there is a "receptor dysfunction" in the spinal cord, the significance of which is poorly understood in terms of the accepted model of steroid hormone action.

Aldosterone↗
PubMed1986

Mineralocorticoid regulation of salt intake is preserved in hippocampectomized rats.

Considering the high concentration of binding sites for [3H]-aldosterone in the hippocampus, a relationship between these sites and the regulation of sodium appetite by aldosterone was investigated. After surgical hippocampectomy, rats showed an approximately 80% depletion of [3H]-aldosterone binding sites. In spite of this reduction, hippocampectomized rats developed a sodium appetite after adrenalectomy; this sodium appetite was suppressed by continuous administration of aldosterone, a response similar to the pattern found in normal rats. These results suggest that the hippocampus is not the main target of the effect of the hormone on salt intake.

Adrenalectomy↗
PubMed1985

Further studies of brain aldosterone binding sites employing new mineralocorticoid and glucocorticoid receptor markers in vitro.

We have used synthetic markers of the glucocorticoid (GC) receptor (RU 28362) and of the mineralocorticoid (MC) receptors (RU 26752 and RU 28318) to characterize the specificity of the sites binding aldosterone (ALDO), dexamethasone (DEX) and corticosterone (CORT) in cytosol of hippocampus. The results obtained suggest that ALDO was bound mostly to a MC receptor, as the relative binding affinity (RBA) of the GC receptor marker (and that of the previously studied RU 26988) was negligible for this site, in contrast to the high RBA displayed by RU 26752. DEX was bound for a large part to a GC receptor, as RU 28362 competed for this site, although the MC receptor marker still showed some affinity. An intermediate effect of both marker types was obtained with CORT. RU 28318 was a weak competitor for either the GC or the MC binding site. Thus, RU 28362 and RU 26752 allowed the discrimination of two to three receptors in the hippocampus, similarly to those described in the kidney. Finally, we have demonstrated the usefulness of these synthetic markers in identifying MC binding sites in several brain regions and also in the hippocampus during ontogenetic development.

Adrenalectomy↗
PubMed1985

Properties and distribution of glucocorticoid-binding sites in cytosol of the spinal cord.

We have examined the spinal cord for the presence of glucocorticoid-binding sites. For this purpose, cytosol from the spinal cord of adrenalectomized rats was incubated with (3H)-dexamethasone. Maximal binding was obtained after 20 h of incubation at 0 degree C in the presence of 20 mM molybdate, whereas at 20 degrees C the maximum was at 2 h. Using a range of (3H)-dexamethasone concentrations (0.2-30 nM), low capacity (161 +/- 23 fmol/mg protein) and high affinity (Kd 3.2 +/- 0.3 nM) sites were measured. Binding sites decreased by 25% and Kd increased 2.5-fold after incubation with a pure glucocorticoid (RU 26988). Relative binding affinities of several competitors of 10 nM (3H)-dexamethasone were: triamcinolone acetonide 108, dexamethasone 100, RU 26988 54, corticosterone 18, progesterone 17, aldosterone 7, estradiol and testosterone less than 1. Sedimentation coefficients in glycerol gradients containing molybdate were in the range of those published for glucocorticoid receptors (9.6-9.8 S). Binding of (3H)-dexamethasone was decreased by omitting a SH-protective agent from the buffer or by addition of SH-blocking reagents such as N-ethylmaleimide and p-chloromercuribenzoate. Using rats of different ages, it was found that binding sites were much lower in spinal cord from 2- to 8-day-old rats than in rats of 13-20 days and adults. Regional distribution studies using cytosol from spinal cords dissected between vertebrae C1-C2, C3-C7, T1-T8, T9-L3 and L4-L6 revealed that binding sites were higher in regions containing the cervical (C3-C7) and lumbar (T9-L3) enlargements, with respect to L4-L6.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1984

Influence of phosphatase inhibitors and nucleotides on [3H]dexamethasone binding in cytosol of human placenta.

The purpose of this investigation was to establish the properties of [3H]dexamethasone binding sites in cytosol of human placenta at term. Cytosol containing 20 mM sodium molybdate (MoO4Na2) was incubated for 120 min at 20 degrees C with 40 nM [3H]dexamethasone. The following properties were observed: (a) a single population of binding sites of high affinity and low capacity was measured by Scatchard analysis; (b) potent glucocorticoids such as dexamethasone and cortisol displaced the tritiated ligand, progesterone showed an intermediate activity, whereas cortisone, testosterone and 17 beta-estradiol were ineffective competitors; (c) ultracentrifugation on 16-41% glycerol gradients containing 20 mM MoO4Na2 yielded sedimentation values of 10.25 +/- 0.35 S (n = 4 placentas); (d) the binding sites could be differentiated from the enzyme 11 beta-hydroxysteroid dehydrogenase, as the activity of the former, but not that of the latter, was greatly dependent on the presence of MoO4Na2 in the incubation medium. Inactivation of binding sites labelled with [3H]dexamethasone by incubation at 20 degrees C was prevented by phosphatase inhibitors such as 20 mM MoO4Na2 (P less than 0.01), 20 mM sodium tungstate (WO4Na2) (P less than 0.01) and to a lower extent by 5 mM ATP and cAMP (P less than 0.05). 50 mM NaF, 5 mM GTP or cGMP had no effect. The protection afforded by MoO4Na2 and WO4Na2 was correlated with a significant inhibition of the activity of acid phosphatase, but not alkaline phosphatase. Neither ATP nor cAMP modified phosphatase activity. It is suggested that binding sites for [3H]dexamethasone in cytosol of human placenta showed properties similar to those described for glucocorticoid receptors in target cells, and that these binding sites are regulated by phosphorylation and dephosphorylation mechanisms.

Acid Phosphatase↗
PubMed1983

The placenta as a glucocorticoid target tissue: exchange assay of (3H)-dexamethasone binding and effect of steroids on receptor content.

Binding of (3H)-dexamethasone was studied in high speed supernatant (HSS) of basal zone trophoblast and labyrinthine zone of rat placenta using an exchange assay. The system showed the following characteristics: (1) maximum binding was attained after 120 min of incubation; (2) molybdate was required in the medium to measure binding sites at 20 degrees C and equilibrium conditions; (3) exchange was near 90-100% between ligand and corticosterone added during a preincubation; (4) low capacity (190-250 fmoles/mg protein), high affinity (Kd 10(-8) M) binders were determined by saturation analysis; (5) competition with other steroids in vitro revealed that in basal zone trophoblast, only dexamethasone displaced the ligand, whereas in labyrinthine zone corticosterone, progesterone and testosterone competed to a smaller degree than dexamethasone. We have also studied the effect of in vivo treatment of pregnant rats for four days with dexamethasone, corticosterone, estradiol, progesterone or testosterone, on (3H)-dexamethasone binding. Of all tested compounds, only dexamethasone treatment (which was suspended 24 h before the experiment to prevent receptor occupancy by exogenous hormone) significantly decreased binding of the tritiated hormone in HSS of labyrinthine zone and basal zone trophoblast. These results suggest that dexamethasone regulates its own receptor in placenta. The physiological aspect of this phenomenon requires elucidation of the role of glucocorticoids on placental function in the rat.

Animals↗
PubMed1983

Identification of mineralocorticoid binding sites in rat brain by competition studies and density gradient centrifugation.

A search for mineralocorticoid binding sites in neural tissue was carried out on the basis of competition by two mineralocorticoid antagonists (spironolactone and glycyrrhetinic acid), a mineralocorticoid agonist (9 alpha-fluorocortisol) and a pure glucocorticoid (RU 26988). The hippocampus was selected for these studies, in view of its preferential concentration of binding sites for [3H]-aldosterone (ALDO) and two glucocorticoids: [3H]-corticosterone (CORT) and [3H]-dexamethasone (DEX). Inhibition studies performed with 5 X 10(-4)-5 X 10(-9) M spironolactone and with 5 X 10(-4)-5 X 10(-8) M glycyrrhetinic acid, showed a dose-response reduction of [3H]-ALDO, [3H]-CORT and [3H]-DEX binding, implying that in brain these compounds did not behave as exclusive ALDO antagonists. Two concentrations of 9 alpha-fluorocortisol (5 X 10(-9) and 2.5 X 10(-8) M) preferentially displaced [3H]-ALDO in comparison to [3H]-DEX or [3H]-CORT. Relative binding affinity (RBA) of 9 alpha-fluorocortisol was also higher for the mineralocorticoid than for the glucocorticoids. RU 26988 (5 X 10(-6)-2.5 X 10(-8)M) gave differential inhibition of the three ligands and its RBA for [3H]-DEX site was twice as high as for [3H]-CORT, and three orders of magnitude higher than for [3H]-ALDO binding sites, thus clearly separating sites for gluco- and mineralocorticoids. Further evidence for the presence of separate binding molecules for mineralo- and glucocorticoids in hippocampal cytosol was provided by ultracentrifugation on 16-41% glycerol gradients containing molybdate, which yielded sedimentation values of 9.88 +/- 0.27 for [3H]-DEX (n = 5), 10.48 +/- 0.27 for [3H]-CORT (n = 9) and 11.3 +/- 0.13 for [3H]-ALDO (n = 7).(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMed1982

Characteristics of aldosterone binding in rat and human serum.

Binding of cortisol and corticosterone by serum proteins is well established, but discrepancies exist regarding aldosterone. We have observed that approximately 1% of 3H-aldosterone incubated with rat serum was bound in a time-dependent process, although it was not competed by a large excess of non-radioactive aldosterone, assessed by Florisil separation or gel filtration on Sephadex G-50 columns. After electrophoresis on cellulose acetate of rat serum incubated with 3H-aldosterone, specific or non-specific binding to protein fractions was not obtained. Further, a 10 000-fold molar excess of aldosterone (10 microM) displaced only 34% of the bound 3H-aldosterone to rat serum, preventing the calculation of the IC50 value. Increasing concentrations of aldosterone (3-83 nM) did not displace 3H-corticosterone bound in rat serum to presumably corticosterone binding globulin (CBG). In contrast, inhibition of this binding by 3-83 nM corticosterone was concentration dependent, showing an IC50 value of 10(-8) M. In normal human serum, binding of 3H-aldosterone demonstrated competition by a 100 and 1 000-fold excess of aldosterone. Displacement curves of 3H corticosterone bound to human serum by 1.7-75 nM corticosterone or 0.05-8.8 microM aldosterone yielded IC50 values in the range of 10(-8) M for corticosterone and 10(-6) M for aldosterone. With horse serum, aldosterone's binding affinity was three orders of magnitude lower than that of corticosterone. These studies suggest that in the rat aldosterone was loosely and weakly bound to a high capacity binder, possibly albumin. In agreement with the work of others, in humans aldosterone may be bound to both CBG and albumin. The current data do not substantiate for the presence of specific aldosterone binding proteins in serum.

Aldosterone↗