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J L Yau

Publications and source records attributed to J L Yau.

7 recordsLinked to original sources
PubMed1992

Central 6-hydroxydopamine lesions decrease mineralocorticoid, but not glucocorticoid receptor gene expression in the rat hippocampus.

The role of hippocampal noradrenergic inputs in the modulation of corticosteroid receptor expression has been investigated. Adult male rats were given central 6-hydroxydopamine (6-OHDA) and the expression of hippocampal mineralocorticoid (MR) and glucocorticoid (GR) receptor mRNA was examined after two weeks by in situ hybridization histochemistry. Expression of MR mRNA was significantly decreased in all subregions of the hippocampus except CA2, but 6-OHDA lesions had no effect on GR mRNA expression. These data reveal differential regulation of the two receptor types by noradrenergic inputs.

Animals↗
PubMed1992

Medial septal cholinergic lesions increase hippocampal mineralocorticoid and glucocorticoid receptor messenger RNA expression.

Loss of the cholinergic innervation of the hippocampus and failure of central (presumably hippocampal) suppressive control of hypothalamic-pituitary-adrenal axis activity are important features of Alzheimer's dementia. We have examined the effects of electrolytic lesions of the medial septal cholinergic innervation on mineralocorticoid (MR) and glucocorticoid (GR) receptor mRNA expression in rat hippocampus using in situ hybridization histochemistry. Expression of both MR and GR mRNA was significantly increased in a subregions of the hippocampus, but not neocortex, with the greatest increase in the CA1 area for MR mRNA and dentate gyrus for GR mRNA. Since glucocorticoids potentiate the effects of neurotoxins in the hippocampus, the increased expression of receptors following loss of cholinergic inputs in Alzheimer's disease may increase hippocampal neuronal vulnerability.

Acetylcholine↗
PubMed1992

11 beta-Hydroxysteroid dehydrogenase in the rat ovary: high expression in the oocyte.

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) catalyses the conversion of physiological glucocorticoids to inactive products, thus modifying the access of glucocorticoids to glucocorticoid and mineralocorticoid receptors. Glucocorticoids may affect ovarian function both indirectly and via binding to ovarian receptors. We have demonstrated 11 beta-HSD bioactivity and mRNA expression in rat ovary in vitro. The enzyme was localized to oocytes and luteal bodies immunohistochemically using two antibodies raised against purified rat liver 11 beta-HSD. These data are supported by in-situ hybridization studies, which also localized 11 beta-HSD mRNA expression to oocytes and luteal bodies. The results suggest that 11 beta-HSD may modulate the effects of glucocorticoid on ovarian function.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1991

11 beta-Hydroxysteroid dehydrogenase mRNA expression in rat kidney.

11 beta-Hydroxysteroid dehydrogenase (11 beta-OHSD) protects nonspecific renal mineralocorticoid receptors from exposure to circulating glucocorticoid in vivo by catalyzing the conversion of corticosterone to inactive 11-dehydrocorticosterone. Although 11 beta-OHSD bioactivity and aldosterone binding sites are found in distal tubular cells, mineralocorticoid receptor and 11 beta-OHSD immunoreactivities are not colocalized. However, there are several kidney isoforms of 11 beta-OHSD, not all of which may be immunoreactive, whereas only a single mRNA species has been described. Using in situ hybridization we found 11 beta-OHSD mRNA is highly expressed in all renal tubular epithelia in the rat. It is therefore likely that 11 beta-OHSD is colocalized with mineralocorticoid receptors in distal tubular cells.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1991

11 beta-hydroxysteroid dehydrogenase in vascular smooth muscle and heart: implications for cardiovascular responses to glucocorticoids.

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) converts the active glucocorticoid corticosterone to inactive 11-dehydrocorticosterone in the rat (or cortisol to cortisone in man), thereby protecting renal mineralocorticoid receptors from corticosterone or cortisol and allowing preferential access for aldosterone. We have previously demonstrated that cortisol-induced cutaneous vasoconstriction in man is potentiated by the 11 beta-OHSD inhibitor glycyrrhetinic acid, suggesting that 11 beta-OHSD may protect vascular corticosteroid receptors. In this study we report quantitation of 11 beta-OHSD bioactivity in homogenates of rat aorta, mesenteric artery, caudal artery, and heart, expressed as the percent in vitro conversion of 3H-corticosterone to 3H-11-dehydrocorticosterone. Nicotinamide adenine dinucleotide phosphate (NADP+)-dependent 11 beta-OHSD activity was found in all of these tissues and was significantly higher in resistance vessels than aorta (P less than 0.05) [without NADP+: caudal artery (4.2 +/- 0.2%) greater than mesenteric artery (2.5 +/- 0.7%) = heart (1.67 +/- 0.2%) greater than aorta (0.79 +/- 0.2%); with 200 microM NADP+: caudal artery (43.9 +/- 2.1%) greater than heart (20.6 +/- 1.0%) = mesenteric artery (17.7 +/- 3.1%) = aorta (11.4 +/- 0.4%); heart greater than aorta]. All of these were lower than renal cortex (29.4 +/- 1.8% without NADP+; 82.4 +/- 0.4% with NADP+; P less than 0.001). 3H-11-dehydrocorticosterone was the major metabolite of 3H-corticosterone (greater than 97% of 3H-corticosterone metabolized). Reduction of 3H-11-dehydrocorticosterone to 3H-corticosterone was not detected in these experiments. We also report localization of 11 beta-OHSD-like immunoreactivity by immunohistochemistry using antisera raised against rat liver 11 beta-OHSD, and of 11 beta-OHSD messenger RNA expression by in situ hybridization using complementary RNA probes transcribed from complementary DNA encoding rat liver 11 beta-OHSD. We found 11 beta-OHSD immunoreactivity and messenger RNA expression in vascular and cardiac smooth muscle cytoplasm but not in endothelium. Thus, 11 beta-OHSD is appropriately sited to modulate access of corticosterone to vascular receptors and could influence vascular resistance, cardiac output and thereby blood pressure.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1990

Modulation of the GABAA receptor by barbiturates and pregnane steroids: differential effects of the influence of assay temperature.

The effect of temperature on the modulation of the GABAA receptor by barbiturates and steroids has been investigated in-vitro using a radioreceptor binding assay. Displaceable [3H]muscimol binding to a crude membrane preparation from rat cerebral cortex was enhanced by the endogenous steroid metabolite, 5 beta-pregnan-3 alpha-ol-20-one, by the synthetic steroid, alphaxalone, and by pentobarbitone in a dose-dependent manner. Hydrocortisone and corticosterone had no significant effect on [3H]muscimol binding. Analysis of binding data using a curve-fitting program ('Ligand') showed that both pentobarbitone (1 mM) and 5 beta-pregnan-3 alpha-ol-20-one (10 microM) increased the apparent number of high affinity binding sites in the membrane but had no effect on the affinity of [3H]muscimol binding (Kd approx. 11 nM). Increasing the assay temperature from 0 degrees C to 35 degrees C decreased [3H]muscimol binding and decreased the enhancement of binding by pentobarbitone but had no effect on 5 beta-pregnan-3 alpha-ol-20-one enhancement of binding. 5 alpha-Pregnan-3 alpha-ol-20-one increased the apparent rate of association of [3H]muscimol binding to its receptor whereas pentobarbitone had no effect. These different effects on the apparent association rate and the different responses to temperature, suggest that the barbiturate and steroid may interact with the GABAA receptor through different binding sites.

Animals↗