摘要:

Steroid hormone synthesis is controlled by two classes of mechanisms.“Acute”regulation entails rapid increases or decreases of steroid synthesis and secretion, principally mediated by rapid changes in the activities of the steroidogenic enzymes and by the availability of the substrate, free cholesterol.“Chronic”regulation entails increases or decreases in the amounts of the steroidogenic enzymes as well as their activities. The amounts of the enzymes are regulated principally by the amounts of the specific mRNAs encoding them. These, in turn, are regulated both transcriptionally and post-transcriptionally. The mRNAs are regulated by hormonal induction, by an ontogenic program, and in a tissue-specific fashion.

ISSN:0743-5800    

DOI:10.1080/07435808909039085

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractAmong the multifactorial aspects of regulation of steroid hydroxylase gene expression, it is the developmental process which leads to imprinting of expression of particular steroid hydroxylases in specific cell types. We have begun to investigate the ontogeny of steroidogenesis in fetal bovine tissues. Expression of most steroid hydroxylases and related enzymes is detectable in adrenals of the smallest fetuses studied and continues throughout fetal life. Like the other steroid hydroxylases, P-45017αis detectable in the earliest fetal adrenals studied. However, following an increase in expression, P-45017αdisappears from the fetal adrenal by 100 days gestational age and remains absent until about 230 days gestational age. The absence of P-45017αis correlated with the absence of cortisol in the fetal adrenal and the absence of ACTH in fetal plasma. Thus expression of P-45017αin bovine fetal adrenal appears to be strictly dependent on cAMP while expression of other steroid hydroxylases appears to involve both cAMP-dependent and cAMP-independent mechanisms. Furthermore, P-45017αis expressed in fetal testis at gestational times when it is absent in fetal adrenal. We have begun to examine binding of nuclear proteins from adrenals of various gestational ages to the 5′-flanking region of the bovine P-45017αgene. Preliminary evidence indicates the presence of a protein in nuclei of fetal adrenals not expressing P-45017αthat is not present in fetal adrenals of other gestational ages.

ISSN:0743-5800    

DOI:10.1080/07435808909039086

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

The steroid 21-hydroxylase (21-OH) gene is selectively expressed in the adrenal cortex and is transcriptionally regulated by ACTH. We examined the role of the 5′-flanking sequences of 21-OH in this regulated expression by analyzing their ability to direct the expression of a human growth hormone (hGH) reporter gene upon transfection into Y1 mouse adrenocortical tumor cells. The 330 bp of 5′-flanking sequences directed basal and hormonally-inducible expression of hGH in Y1 cells, but did not direct expression in I-10 mouse testicular Leydig cells. Both constitutive and hormonally-inducible expression required a functional cAMP-dependent protein kinase. These results indicate that the first 330 bp of 5′-flanking sequences of the 21-OH gene contain sufficient information for cell-specific and hormonally regulated expression, and that this expression requires the integrity of cAMP-dependent protein kinase. Markedly lower expression of hGH was seen when 156 bp of 5′-flanking sequences were placed in front of the reporter gene, suggesting that sequences between -330 and -156 are essential for expression. The addition of sequences from -330 to -150 to the p-156GH plasmid, in either the correct or the reverse orientation, restored promoter activity to approximately the level obtained with the 330 bp of 5′-flanking sequences. Moreover, the addition of sequences from -230 to -150 increased by 5-fold the expression of hGH driven by the heterologous thymidine kinase promoter. Based on these results, we conclude that an enhancer element is contained within the sequences from 230 to 150 bp upstream of the transcription initiation site.

ISSN:0743-5800    

DOI:10.1080/07435808909039087

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe cause and effect relationship between mutations in cAMP-dependent protein kinase activity and resistance of adrenocortical tumor cells to ACTH and cAMP was evaluated by transfection with cloned cDNAs encoding subunits of the mouse cAMP-dependent protein kinase. Protein kinase defective, Kin 8 adrenocortical tumor cells were transfected with pRev [an expression vector encoding the regulatory subunit of the type 1 cAMP-dependent protein kinase (R1)] or with pCαev [an expression vector encoding the catalytic subunit of cAMP-dependent protein kinase (c)]. The pCαev transformant recovered cAMP responsive protein kinase activity, whereas the pRev transformant recovered cAMP-binding activity, but did not recover cAMP responsive protein kinase activity. The pCαev transformant concomitantly recovered steroidogenic and morphologic responsiveness to ACTH- and 8-bromo-cAMP, whereas the pRev transformant remained resistant to these effects of the hormone and cyclic nucleotide. Since Kin 8 cells recovered their responsiveness to ACTH and 8-bromo-cAMP following

ISSN:0743-5800    

DOI:10.1080/07435808909039088

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

The results presented indicate that purified cytochrome P-45021which migrated upon SDS gel electrophoresis essentially as a single band, is further separable into different species by ion-exchange chromatography. The P-450 eluted from the CM-Sephadex column at different points along the buffer concentration gradient, exhibited significant differences in (1) the 21-hydroxylation of 17α-OH-progesterone compared to progesterone and (2) the Type I spectral change produced by 17α-OH-progesterone compared to that due toΔ4-androstenedione. These results indicate that the purified P-450 which appeared homogeneous contains different species differing in net charge and steroid preferences for 21-hydroxylation and binding. The ratio, 21-hydroxylation of 17α-OH-progesterone/progesterone ranged between 2.6 and 0.86 suggesting that the purified preparation is a mixture of 17α-OH-progesterone preferring and progesterone preferring species. Possible molecular bases for the heterogeneity of the 21-hydroxylase are discussed.

ISSN:0743-5800    

DOI:10.1080/07435808909039089

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

ABSTRACTCholesterol sulfate is a naturally occurring compound which is widely distributed among various tissues including the adrenal cortex. When added to adrenal mitochondria from ether-stressed rats, it inhibits pregnenolone synthesis from exogenous but not endogenous cholesterol. Evidence supports a locus of action at the level of an intramitochondrial cholesterol translocation system with no effect on the side-chain cleavage enzymatic system (cytochrome P-450scc). Levels of endogenous cholesterol sulfate in the adrenal are similar to the Ki for inhibition by this compound, suggesting a possible physiological role. Moreover, quantities of cholesterol sulfate present in isolated mitochondria from ether-stressed animals are variable, and levels correlate inversely with rates of pregnenolone production by these preparations. In the presence of malate, mitochondrial cholesterol sulfate is metabolized slowly to pregnenolone sulfate, and its removal correlates with activation of cholesterol side-chain cleavage. Cholesterol sulfate levels are not regulated acutely by stress, but can be decreased significantly after several weeks of daily injection of ACTH (a model of chronic stress). Such treatments result in an increased capacity of isolated adrenal mitochondria to synthesize pregnenolone, and increased activity correlates with increased levels of circulating corticosterone. Thus, we propose that cholesterol sulfate is a new physiological regulator of steroid hormone biosynthesis which may function to regulate the magnitude of the steroidogenic response of the adrenal cortex to ACTH.

ISSN:0743-5800    

DOI:10.1080/07435808909039090

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractCholesterol side-chain cleavage is sensitive to antibiotic inhibitors of protein synthesis, suggesting that a labile protein may play a regulatory role in this process. We have previously characterized such a factor - steroidogenesis activator polypeptide (SAP). Given the low molecular weight of SAP (Mr3215), a SAP precursor has been sought. Using immunoblotting techniques with two polyclonal antisera directed against portions of the SAP sequence, a single protein of apparentMr82,000 (p82) can be detected in rat adrenocortical tissue. Our data suggest that adrenal p82 is most likely the widely-distributed minor heat shock protein, glucose regulated protein 78 (GRP78). The two proteins share biochemical attributes, includingpI (5.2) and ATP affinity, and the reported amino acid sequences for SAP and for the carboxyl-terminal end of GRP78 are nearly identical. We propose that SAP is cleaved from GRP78 - or a cognate protein - and that this proteolysis is regulated in a manner characteristic of steroidogenic tissues.

ISSN:0743-5800    

DOI:10.1080/07435808909039091

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

We have reported previously that a protein, ib, is produced in adrenal cortex and other steroidogenic cells with the same tissue-specific peptide hormone or cAMP dose-response and the same kinetics as the increase in steroid hormone biosynthesis. In this study, we have fractionated adrenal cortex cells into subcellular components and used two-dimensional electrophoresis to characterize the proteins in these fractions. We have demonstrated previously that inhibition of cytosolic translation, e.g. by cycloheximide, prevents the production of protein ib. We also report that the production of this protein is not affected by inhibition of mitochondrial translation by chloramphenicol.

ISSN:0743-5800    

DOI:10.1080/07435808909039092

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

Corticostatins (CS's) are a family of low molecular weight peptides, rich in arginine and cysteine with the ability to inhibit ACTH stimulated adrenocortical steroidogenesis (1). They show a high degree of specificity in that they do not inhibit the action of angiotensin II in the adrenal cortex. Four corticostatins have been isolated from rabbit lung extracts and peritoneal neutrophil extracts and one from human neutrophils. Among them corticostatin I, CSI, is the most potent with an I.D.50of 25 nM. Corticostatin activity is different from other published inhibitory factors such as TGF-B and ANF, which inhibit basal and angiotensin II stimulated steroidogenesis (2,3,4). Other factors such as macrophage secreted products (5,6), and septic shock plasma factors (7) which have not been fully characterized also have suppressive activity on ACTH induced adrenocortical steroidogenesisin vitro. It is not yet clear whether there is any relationship between corticostatins and these macrophage products and shock plasma factor. Corticostatins do not inhibit dbcAMP induced steroidogenesis, however they do inhibit the accumulation of cAMP in response to ACTH in rat adrenal cell suspensions. Binding studies show that CSI is a competitive inhibitor of ACTH, probably acting by blocking, the address recognition site of the receptor. There is wide variation in the potency of the corticostatins ranging from an ID50of 100 ng/ml for CSI to a completely inactive analog, HP1. In this paper we will describe the purification of the corticostatins and some recent results obtained on their mechanism of action.

ISSN:0743-5800    

DOI:10.1080/07435808909039093

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractUrines of patients with primary aldosteronism were extracted, the extract repeatedly chromatographed with reversed phase HPLC. The fractions immunoactive against 18-hydroxycorticosterone antiserum and being more polar than the 18-hydroxycorticosterone were further purified, derivatized and investigated by GC/MS. In this manner the natural occurence of the 18,19-dihydroxycorticosterone, which was lately synthetized, in human urine was confirmed.

ISSN:0743-5800    

DOI:10.1080/07435808909039094

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor