Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Platelet-derived growth factor (PDGF) is a potent mitogen for several cell types. In addition, PDGF has vasoconstrictive action and shares some signal transduction mechanisms with angiotensin II (AII). In the present study, we have examined the effects of PDGF on basal and AII-induced aldosterone synthesis in freshly isolated rat adrenal glomerulosa cells. Recombinant human PDGF-BB caused a dose-dependent inhibition of AII-induced aldosterone synthesis being effective at concentrations as low as 10(-12) M. We also investigated possible mechanisms of action of PDGF. We have previously reported that the 12-lipoxygenase (LO) pathway of arachidonic acid plays a key role in AII-induced aldosterone synthesis. We thus examined whether PDGF action is mediated by changes in 12-LO activation. PDGF, at the same doses that blocked AII-induced synthesis also significantly inhibited AII-induced increases in the 12-LO product, 12-hydroxyeicosatetraenoic acid (12-HETE) formation. Further, the addition of 12-HETE completely restored the stimulatory effect of AII during inhibition by PDGF. These results suggest that PDGF could act, at least in part, by inhibition of AII-induced 12-HETE formation. We also examined the role of diacylglycerol (DG) formation since we have previously reported that DG is the source of arachidonic acid for 12-HETE formation. We observed that both AII and PDGF stimulated [3H]arachidonic acid-labeled DG formation. However, PDGF did not alter AII-induced DG formation suggesting that PDGF action is not mediated by affecting AII-induced increases in DG.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1992 Jan
PMID:Platelet-derived growth factor is a potent inhibitor of angiotensin II-induced aldosterone synthesis. 131 60

Adrenalectomy blocks the memory-improving effect of piracetam-like compounds in mice. If this blockade is due to the removal of endogenous corticosteroids, replacement therapy with exogenous corticosteroids should reinstate the effects on memory. The present experiments were designed to determine the appropriate replacement dose (concentration in the drinking fluid) for corticosterone and aldosterone, the main corticosteroids in mice. Based on the effects of corticosterone on thymus weight, replacement with 3 micrograms/ml corticosterone given in the drinking fluid (0.9% NaCl) for one week was found to be appropriate. The appropriate replacement dose for aldosterone was found by giving aldosterone to adrenalectomized (ADX) mice in the drinking fluid in combination with 3 micrograms/ml corticosterone. The combination of 3 micrograms/ml corticosterone + 30 ng/ml aldosterone resulted in a plasma ratio of corticosterone/aldosterone which most closely approximated the ratio seen in sham-ADX control animals. The physiologic adequacy of the corticosteroid replacement doses resulting from this study were clearly demonstrated in subsequent behavioral experiments where blockade of the memory-enhancing effects of piracetam by adrenalectomy were overcome by replacement with either 3 micrograms/ml corticosterone or 30 ng/ml aldosterone given in the drinking fluid.
J Steroid Biochem Mol Biol 1992 Mar
PMID:Adrenalectomy, corticosteroid replacement and their importance for drug-induced memory-enhancement in mice. 131 83

We have previously reported that mineralocorticosteroid receptor (MR) is a 8-9 S heterooligomeric complex that includes the 90 kDa heat shock protein (hsp90). To elucidate how antagonist-receptor complexes are biologically inactive in terms of transcriptional regulation, we analyzed the binding of mineralocorticosteroid agonists and antagonists with MR and the ligand-induced transformation of its heterooligomeric structure. This study was performed in the cytosol of adrenalectomized rat kidney and of COS cells transiently transfected with human MR cDNA. Although aldosterone antagonists (SC9420 and RU26752) bind MR with the same affinity as aldosterone, they dissociate much more rapidly from the 8-9 S form of both rat and human MR than does aldosterone. Using sedimentation gradient analysis, we showed that the interaction between hsp90 and the steroid binding subunit of MR is highly dependent upon the nature of the steroid ligand since the binding of aldosterone antagonists results in an easy release of hsp90. We propose that both rapid dissociation of ligand and weakened hsp90-receptor interaction play a key role in the mechanism of mineralocorticosteroid antagonism. In the COS cell model, cortisol, described as a weak mineralocorticosteroid agonist, dissociates also more rapidly from human MR than does aldosterone. Our results suggest that ligand binding kinetics and ligand dependent modification in receptor structure are important modulators of MR function as a transcriptional regulatory factor.
J Steroid Biochem Mol Biol 1992 Mar
PMID:Differences between aldosterone and its antagonists in binding kinetics and ligand-induced hsp90 release from mineralocorticosteroid receptor. 131 85

This study investigated the effects of the calcium channel blockers nifedipine (a dihydropyridine) and verapamil (a papaverine derivative), on aldosterone production utilizing isolation of the early and late phases of aldosterone biosynthesis. Pregnenolone production (the early phase of aldosterone biosynthesis) was assessed in trilostane-treated bovine glomerulosa cells, used to inhibit the conversion of pregnenolone onwards to aldosterone. Conversion of exogenous corticosterone to aldosterone, an index of late phase activity, was assessed using aminoglutethimide to inhibit endogenous aldosterone production. Low concentrations of nifedipine, 10(-11)-10(-9) M, stimulated basal total aldosterone biosynthesis by enhancing the late phase although the early phase was inhibited. In the presence of 12 mM potassium (K+), which is less effective in stimulating aldosterone production than lower K+ concentrations, aldosterone production was enhanced by nifedipine, 10(-8) M, by an effect on the late phase. At K+ 6 and 8 mM, nifedipine, 10(-4) M, inhibited the early phase. Nifedipine 10(-5) inhibited angiotensin II (AII)-stimulated total aldosterone biosynthesis by independent effects on the early and late phases. Verapamil, 10(-4) M, inhibited total and early phase aldosterone production at K+, 4 mM and inhibited both phases at K+, 8 mM, stimulation was not observed using verapamil. Verapamil, 10(-4) M, also inhibited AII-stimulated aldosterone production. Basal and AII-stimulated pregnenolone production were inhibited by verapamil, 10(-4) M (basal) and 10(-6) M (AII-stimulated). These studies using nifedipine have revealed subtle calcium-dependent mechanisms involved in the tonic inhibition of activity in the late phase of aldosterone biosynthesis and the reversal of the inhibitory effect of high K+ concentrations also on the late phase. In addition, the data reported indicate that both AII and K+ independently enhance activity in the early and late phases of aldosterone production by calcium-dependent mechanisms.
J Steroid Biochem Mol Biol 1992 Jul
PMID:Evidence for a tonic inhibitory role of nifedipine-sensitive calcium channels in aldosterone biosynthesis. 132 60

The intracellular mechanisms of action of alpha-MSH in rat adrenocortical cells were examined. When rat adrenal capsule (largely glomerulosa) cells were stimulated with a range of concentrations of alpha-MSH there was significant stimulation of aldosterone secretion at 10(-10) mol/l, although cyclic AMP was not increased until high concentrations of alpha-MSH were used (10(-6) mol/l and above). However, cells incubated with ACTH showed an increase in aldosterone secretion at 10(-11) mol/l and levels of cyclic AMP were elevated at 10(-9) mol ACTH/l. When rat adrenal whole capsules were incubated with alpha-MSH, membrane-bound protein kinase C (PKC) activity was increased and cytosolic enzyme activity decreased, showing PKC activation. Stimulation with angiotensin II also induced translocation of PKC activity, but ACTH did not. When [3H]inositol-loaded glomerulosa cells were stimulated with alpha-MSH there was significant generation of [3H]inositol trisphosphate (IP3) at concentrations of alpha-MSH which stimulated secretion of aldosterone. Significantly increased levels of [3H]IP3 were also measured when loaded cells were exposed to angiotensin II. ACTH did not cause any significant stimulation of [3H]IP3 production at any concentration used. These results indicate that activation of PKC and phospholipase C is important in modulating the steroidogenic effect of alpha-MSH.
J Mol Endocrinol 1992 Aug
PMID:Studies on the intracellular mechanism of action of alpha-melanocyte-stimulating hormone on rat adrenal zona glomerulosa. 132 51

A 167 amino acid fragment of the N-terminal domain of the human type I corticosteroid (mineralocorticoid) receptor was fused to the glutathione S-transferase gene using the Gex expression plasmid and the fusion protein used to raise the monospecific polyclonal antibody, MINREC4. Immunostaining experiments showed that MINREC4 specifically bound type I receptor in the distal tubule of the kidney, the ductal elements of the salivary glands and the epithelium of the distal colon in the rat. Adrenalectomy abolished staining in the parotid and colon, and reduced immunoreactivity in the submandibular gland. Administration of corticosterone or aldosterone resulted in partial restoration of immunostaining in the parotid, and a complete restoration of staining to intact levels in the submandibular gland and colon. These results suggest that adrenocorticoid binding to the type I receptor may result in tissue specific conformational changes in the binding protein and that the MINREC4 antibody may be used to study the effects.
Mol Cell Endocrinol 1992 May
PMID:Type I corticosteroid receptor-like immunoreactivity in the rat salivary glands and distal colon: modulation by corticosteroids. 132 51

The high selectivity, low conductance, amiloride-blockable, sodium channel of the mammalian distal nephron (i.e. cortical collecting tubule) is the site of discretionary regulation which allows maintainance of total body sodium balance. In order to understand the physiological events that participate in this regulation, we have used the patch-clamp technique which allows us to measure individual Na+ channel currents and permits access to the cytosolic side of the channel-protein as well as its associated regulatory components. Most of our experiments have utilized the A6 amphibian renal cell line, which when grown on permeable supports is an excellent model for the mammalian distal nephron. Different mechanisms have been examined: (1) regulation by hormonal factors such as Anti-Diuretic Hormone (ADH) and aldosterone, (2) regulation by G-proteins, (3) modulation by protein kinase C (PK-C), and (4) modulation by products of arachidonic acid metabolism. Consistent with noise analysis of tight epithelial tissues, ADH treatment increased the number of active channels in apical membrane patches of A6 cells, without any apparent change in the open probability (Po) of the individual channels. Agents that increased intracellular cAMP mimicked the effects of ADH. In contrast, aldosterone was found to act through a dramatic increase in Po rather than through changes in channel density. Inhibition of methylation by deazaadenosine antagonizes the stimulatory effect of aldosterone. In excised inside-out patches GTP gamma S inhibits channel activity, whereas GDP beta S or pertussis toxin stimulates activity suggesting regulatory control by G-proteins. PK-C has been shown to contribute to 'feed-back inhibition' of apical Na+ conductance in tight epithelia.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1992 Sep 08
PMID:Regulation of renal epithelial sodium channels. 133 27

The adrenal glomerulosa cell is a major site of action of angiotensin II (AII), which binds to AT1 receptors to stimulate phosphoinositide hydrolysis and Ca2+ mobilization, and the subsequent production of aldosterone. All also influences adrenal growth and proliferation and promotes thymidine incorporation in adrenocortical cells. In primary cultures of bovine glomerulosa cells, AII was found to induce the expression of several early growth response genes (c-fos, c-jun, JunB, and Krox 24). This effect of AII was dose-dependent and was blocked by [Sar1,IIe8] AII and the nonpeptide antagonist DuP 753, indicating that it is mediated by the AT1 subtype of the AII receptor. ACTH, which elevates cAMP in glomerulosa cells, was a relatively weak inducer of c-fos expression but was as potent as AII in stimulating the expression of JunB. ACTH did not further enhance the maximal effect of AII on c-fos expression. The role of the AII-induced cytoplasmic Ca2+ increase in generating the c-fos response was suggested by the ability of the Ca2+ ionophore ionomycin to induce c-fos expression. However, mobilization of intracellular Ca2+ by the Ca2+ ATPase inhibitor thapsigargin, as well as the stimulation of Ca2+ influx by depolarization with potassium, were less potent stimuli of c-fos expression. Omission of Ca2+ from the extracellular medium, which abolishes the plateau phase of the AII-induced Ca2+ signal without affecting the early increase due to Ca2+ mobilization, enhanced the early phase of the AII-induced c-fos response, indicating that Ca2+ also has an inhibitory effect on the early gene response. Activation of protein kinase C by phorbol 12-myristate, 13-acetate (PMA) also stimulated c-fos expression, but the combination of PMA and ionomycin did not further increase the c-fos response. Inhibition of protein kinase C by staurosporine, or its depletion by prolonged exposure to PMA, prevented the c-fos response to PMA but only partially inhibited the response to AII, suggesting the involvement of other factors in stimulus-transcription coupling from the AT1 receptor.
Mol Endocrinol 1992 Nov
PMID:Stimulation of early gene expression by angiotensin II in bovine adrenal glomerulosa cells: roles of calcium and protein kinase C. 133 25

Functional studies in extrarenal, non-epithelial cells such as smooth muscle cells and more recently circulating human lymphocytes have provided increasing evidence that aldosterone produces not only classical genomic effects, but also rapid, non-genomic effects on transmembrane electrolyte movements. These involve activation of the sodium/proton exchanger of the cell membrane at very low, physiological concentrations of aldosterone with an acute onset within 1-2 min. A second messenger cascade involved is the inositol 1,4,5-trisphosphate/calcium pathway which responds over the same rapid time course. Such changes clearly cannot be explained by genomic mechanisms, which are responsible for later effects than the membrane related rapid responses. The mechanisms underlying these rapid effects of aldosterone on electrolytes have been extensively studied in human lymphocytes, which thus may represent valuable tools in the delineation of the receptor-effector mechanisms involved. The unique characteristics of this new pathway for steroid action include its rapid time course, 10,000-fold selectivity for aldosterone over cortisol and the ineffectiveness of spironolactones, classical mineralocorticoid antagonists, as antagonists of the response.
Mol Cell Endocrinol 1992 Dec
PMID:Aldosterone-specific membrane receptors and rapid non-genomic actions of mineralocorticoids. 133 26

The role of AII receptors subtypes, AT1 and AT2, in the regulation of aldosterone secretion was studied in adrenal glomerulosa cells and membranes from rats on normal and low sodium intake, using AII receptor subtype-specific antagonists. In adrenal glomerulosa cells, more than 90% of the receptors were AT1 and there was a good correlation between the potencies of the antagonists to inhibit ligand binding, and AII-stimulated aldosterone production and inositol phosphate formation. The inhibition of basal and ACTH-stimulated cAMP by AII was also abolished by the AT1, but not the AT2, antagonist. Sodium restriction for 6 days increased both receptor subtypes in the same proportion, but only the AT1 antagonist inhibited AII-stimulated aldosterone production. The data demonstrate that AT1 receptor mediates the regulatory actions of AII in the adrenal zona glomerulosa.
Mol Cell Endocrinol 1992 Dec
PMID:Role of angiotensin II receptor subtypes on the regulation of aldosterone secretion in the adrenal glomerulosa zone in the rat. 133 30


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