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At least 1,153 records · Page 64Linked to original sources
PubMed1992

The structure and activity of two cytochrome P450c21 proteins encoded in the ovine adrenal cortex.

The steroidogenic enzyme cytochrome P450c21 (CYP21A1) is synthesized in the adrenal cortex and is essential for cortisol and aldosterone production. We have studied the structure and activity of ovine P450c21 proteins by analysis and expression of the corresponding cDNAs. Two P450c21 mRNAs (2.2 and 1.7 kilobases) were detected in ovine adrenal RNA and corresponded to two types of P450c21 cDNA clones that differed in their 3' region. One clone encoded a protein similar in structure to bovine, murine, and human P450c21 proteins. The other clone contained a 3' deletion of about 500 nucleotides and encoded a P450c21 protein that was truncated by 18 residues at the carboxyl terminus. The boundaries of this deletion suggested that an additional splicing event was responsible for the shortened mRNA sequence. Detailed Southern analysis of ovine genomic DNA indicates that the two mRNAs are derived from one gene even though two P450c21 genes are present in the ovine genome. The activities of the two P450c21 proteins were determined by expressing the respective cDNA clones in COS cells. The complete P450c21 protein was an efficient catalyst of 21-hydroxylation reactions, whereas no 21-hydroxylation activity was detected in cells containing the P450c21 protein with the carboxyl-terminal deletion.

Adrenal Cortex↗
PubMed1982

Steroidogenic electron transport in adrenal cortex mitochondria.

The flavoprotein NADPH-adrenodoxin reductase and the iron sulfur protein adrenodoxin function as a short electron transport chain which donates electrons one-at-a-time to adrenal cortex mitochondrial cytochromes P-450. The soluble adrenodoxin acts as a mobile one-electron shuttle, forming a complex first with NADPH-reduced adrenodoxin reductase from which it accepts an electron, then dissociating, and finally reassociating with and donating an electron to the membrane-bound cytochrome P-450 (Fig. 9). Dissociation and reassociation with flavoprotein then allows a second cycle of electron transfers. A complex set of factors govern the sequential protein-protein interactions which comprise this adrenodoxin shuttle mechanism; among these factors, reduction of the iron sulfur center by the flavin weakens the adrenodoxin-adrenodoxin reductase interaction, thus promoting dissociation of this complex to yield free reduced adrenodoxin. Substrate (cholesterol) binding to cytochrome P-450scc both promotes the binding of the free adrenodoxin to the cytochrome, and alters the oxidation-reduction potential of the heme so as to favor reduction by adrenodoxin. The cholesterol binding site on cytochrome P-450scc appears to be in direct communication with the hydrophobic phospholipid milieu in which this substrate is dissolved. Specific effects of both phospholipid headgroups and fatty acyl side-chains regulate the interaction of cholesterol with its binding side. Cardiolipin is an extremely potent positive effector for cholesterol binding, and evidence supports the existence of a specific effector lipid binding site on cytochrome P.450scc to which this phospholipid binds.

Adrenal Cortex↗
PubMed1991

Localization of the gene transcripts of 11 beta-hydroxylase and aldosterone synthase in the rat adrenal cortex by in situ hybridization.

Using in situ hybridization, localization of the gene transcripts of 11 beta-hydroxylase and aldosterone synthase was investigated in order to clarify the sites for the synthesis of corticosterone (glucocorticoid) and aldosterone (mineralocorticoid) in the rat adrenal cortex. The gene transcript of 11 beta-hydroxylase was localized in all the endocrine cells of the entire adrenal cortex, while that of aldosterone synthase was exclusively confined in zona glomerulosa cells. These results represent that every endocrine cell of all the cortical zones synthesizes 11 beta-hydroxylase which converts 11-deoxycorticosterone to corticosterone, and only glomerulosa cells synthesize aldosterone synthase which produces aldosterone from corticosterone. Thus it is clearly shown that zona glomerulosa cells synthesize mineralocorticoid, while zona fasciculata as well as reticularis cells produce glucocorticoid.

Adrenal Cortex↗
PubMed1996

Identical origin of adrenal cortex and gonad revealed by expression profiles of Ad4BP/SF-1.

BACKGROUND: Ad4BP/SF-1 was originally identified as a steroidogenic tissue-specific transcription factor. Recent gene disruption studies with the mammalian Ftz-F1 gene encoding Ad4BP/SF-1 clearly revealed the essential function of the factor for adrenal and gonadal differentiation. RESULTS: In this study, we examined the early development of these tissues using Ad4BP/SF-1 as the marker. In rat foetuses of 11.5 days post-coitum (d.p.c.), a cell population designated adrenogenital primordium was firstly observed on symmetrical lines extending from the dorsal aorta to the dorsal coelomic epithelia of the primitive urogenital ridges. From 12.5 d.p.c., the rostral half of the adreno-genital primordium started to separate into two distinct cell populations. Judging from the distribution of primordial germ cells, the cell population on the dorsal aortal side is a primordium for the adrenal cortex whereas that on the coelomic epithelial side is for the gonads. At 13.5 d.p.c., these two primordia have separated completely. CONCLUSION: These observations clearly identified a novel adreno-genital primordium from which both the adrenal cortex and the gonads originate. An RT-PCR study conducted to detect adrenal- and gonad-specific mRNAs supported the above observations.

Adrenal Cortex↗
PubMed1985

Binding sites for inositol trisphosphate in the bovine adrenal cortex.

Binding sites for inositol trisphosphate (IP3) have been identified in bovine adrenal cortex, employing [32P]IP3 prepared from human erythrocytes radiolabeled with [32P]ATP. IP3 was bound to adrenal microsomes with high affinity (Kd = 5 nM) and low capacity (186 fmol/mg protein). During kinetic studies, half-maximal binding was reached in less than one min at 4 degrees C, and dissociation was even more rapid with t1/2 of about 10 sec. [32P]IP2 showed no binding to the microsomal sites, which represent putative receptors at which IP3 acts to elevate intracellular calcium concentration during the actions of peptide hormones such as angiotensin II.

Adrenal Cortex↗
PubMedDate not supplied

[Decrease in the intensity of the EPR cytochrome P-450, adrenodoxine and free radical signals in the adrenal cortex of dogs under the effect of o,p-dichlorodiphenyldichloroethane].

A study was made of the action of the adrenocorticolytic drug chloditane (o.p'-DDD) on the content of cytochrome P-450 adrenodoxine and free radicals in the dog adrenal cortex. After a single feeding of 50 mg/kg bw o.p'-DDD EPR signals with xi-factors 2.25, 1.94 and 2.00 reduced 30-40%. Three-fold feeding of the drug in a dose of 100 mg/kg bw produced a further demonstrable decrease of signals. These changes attest to a possible inhibition of the hydroxylase complex in the adrenal cortex induced by o.p'-DDD.

Adrenal Cortex↗
PubMed2006

Reciprocal regulation of a glucocorticoid receptor-steroidogenic factor-1 transcription complex on the Dax-1 promoter by glucocorticoids and adrenocorticotropic hormone in the adrenal cortex.

Numerous genes required for adrenocortical steroidogenesis are activated by the nuclear hormone receptor steroidogenic factor 1 (SF-1) (NR5A1). Dax-1 (NR0B1), another nuclear hormone receptor, represses SF-1-dependent activation. Glucocorticoid products of the adrenal cortex provide negative feedback to the production of hypothalamic CRH and pituitary ACTH. We hypothesized that glucocorticoids stimulate an intraadrenal negative feedback loop via activation of Dax-1 expression. Reporter constructs show glucocorticoid-dependent synergy between SF-1 and glucocorticoid receptor (GR) in the activation of Dax-1, which is antagonized by ACTH signaling. We map the functional glucocorticoid response element between -718 and -704 bp, required for activation by GR and synergy with SF-1. Of three SF-1 response elements, only the -128-bp SF-1 response element is required for synergy with GR. Chromatin immunoprecipitation (ChIP) assays demonstrate that dexamethasone treatment increases GR and SF-1 binding to the endogenous murine Dax-1 promoter 10- and 3.5-fold over baseline. Serial ChIP assays reveal that that GR and SF-1 are part of the same complex on the Dax-1 promoter, whereas coimmunoprecipitation assay confirms the presence of a protein complex that contains both GR and SF-1. ACTH stimulation disrupts the formation of this complex by abrogating SF-1 binding to the Dax-1 promoter, while promoting SF-1 binding to the melanocortin-2 receptor (Mc2r) and steroidogenic acute regulatory protein (StAR) promoters. Finally, dexamethasone treatment increases endogenous Dax-1 expression and concordantly decreases StAR expression. ACTH signaling antagonizes the increase in Dax-1 yet strongly activates StAR transcription. These data indicate that GR provides feedback regulation of adrenocortical steroid production through synergistic activation of Dax-1 with SF-1, which is antagonized by ACTH activation of the adrenal cortex.

Adrenal Cortex↗
PubMed1992

Ultrastructural evidence for a paracrine regulation of the rat adrenal cortex mediated by the local release of catecholamines from chromaffin cells.

The adrenal glands of perfusion fixed rats were investigated by light and electron microscopy. Within the rat adrenal cortex occurred rays and islets of chromaffin cells which were in close contacts with cortical cells on the electron microscopical level. We achieved to catch the process of exocytosis from a chromaffin cell located within the zona glomerulosa in direct apposition with an adrenocortical cell. The documentation of an exocytotic process from a chromaffin cell neighbouring a cortical cell provides direct evidence in support of a paracrine regulation of the cortex mediated by chromaffin cells.

Adrenal Cortex↗