Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0338671 (Steroids)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The 5alpha reductase activity ofthe monkey epididymis was studied. The enzyme was found in particulate subcellular fractions, its distribution closely resembling that of the microsomal marker enzyme NADPH: cytochrome c reductase, suggesting an association of 5alpha reductase with membranes of the endoplasmic reticulum. Maximal enzyme activity was found at pH 5.4 and at 32--37 C. The crude nuclear preparation had a Km: 0.315 x 10(-6)M and Vmax: 168 pmoles/mg protein/h. The microsomal enzyme had a Km: 0.243 x 10(-6)M and Vmax: 828 pmoles/mg protein/h. Neither enzyme preparation was affected by addition to the incubation media of dihydrotestosterone (DHT) or 5alpha-androstane-3alpha,17beta-diol. The endogenous androgen concentration in the epididymides of 2 different monkeys, in ng/g wet weight was: DHT 20.81 +/- 1.98; T: 9.0L +/- 2.83; diol: 3.03 +/- 0.41.
Steroids 1978 Jan
PMID:Androgen concentration and partial characterization of 5alpha reductase in the epididymis of the rhesus monkey. 2 92

Microsomes prepared from rat uterine homogenates harbor high-affinity (Ka = 10(10) M-1), low-capacity binding sites for estrogens. Previous work from our laboratory has demonstrated that these estrophiles are located on endoplasmic reticulum and are not cytosolic contaminants of the membrane preparation. Subfractionation of microsomes into granular and agranular membranes and polysomes revealed approximately equal distribution of estrogen-binding activity among each of these constituents. These binding sites were fully extractable with 0.6 M KCl. Microsomal estrophiles solubilized under conditions of low ionic strength and complexed with estradiol migrated as 8S forms on continuous sucrose gradients. In the presence of 0.4 M KCl, the solubilized binding sites exhibit a sedimentation coefficient of 4S. Extracted binding sites do not undergo heat-induced transformation from a 4S to 5S species. The monoclonal antibody JS34/32 interacted with the endoplasmic reticulum-associated estrogen-binding sites when present in 50-fold molar excess, but not at lower antibody to binding site ratios. In comparison, the rat uterine cytosolic estrogen receptor formed complexes with JS34/32 at antibody to receptor ratios as low as 2:1. These results suggest that the endoplasmic reticulum possesses estrogen-binding sites with biochemical properties that differ from those of the classically described cytosolic (loosely associated nuclear) estrogen receptor.
Steroids 1991 Feb
PMID:Characterization of estrogen-binding sites associated with the endoplasmic reticulum of rat uterus. 202 Sep 79

Ventral prostate was used as a system to study the nature and properties of microsomal androgen receptor. The endoplasmic reticulum from rat ventral prostate contains high-affinity, low-capacity binding sites for androgen that are intrinsic to this intracellular compartment. Microsomal androgen receptors are not due to plasma membrane or cytosol contamination and they display a fast turnover, with depletion after 1 hour and complete replenishment 6 hours after androgen stimuli. Cycloheximide, but not actinomycin D, inhibits microsomal androgen receptor replenishment, indicating that testosterone may control microsomal receptor levels acutely by posttranscriptional mechanisms. Microsomal androgen receptor is a 5S protein that has a higher stability than its cytosolic counterpart, regardless of the presence of ligand. It does not become activated after heat or salt treatment. After extraction of binding sites, microsomes are capable of accepting cytosol mibolerone-receptor complexes to a level similar to the concentration of depleted binding sites; microsomes from nontarget tissues do not manifest such capability. The results indicate the coexistence of a non-DNA-binding form of androgen receptor in the microsomal membranes with the typical DNA-binding form of androgen receptor present in the cytosol of ventral prostate homogenates. Microsomal androgen receptor may represent an additional level of regulation of androgen action in the intact target cell.
Steroids 1991 Feb
PMID:Role of microsomal receptors in steroid hormone action. 202 Sep 80

Morphologic changes at the interface of rat endometrial luminal epithelial cells and the stromal cells immediately adjacent were examined and correlated with hypertrophy of the epithelial cells during estradiol (E2) infusion (1 microgram E2/24 h). While the lamina densa in castrate endometrium was thread-like, it became thicker and apparently more granular in some areas below the luminal epithelium during E2 infusion. However, no changes were seen in the intensity of laminin-like immunoreactivity at various time points up to 96 hours after beginning infusion, suggesting that these alterations were due to changes in nonlaminin components. The stromal cells adjacent to the basal lamina in the castrate state had cell processes extending toward the epithelium that terminated on the basal lamina. Under estrogen infusion, stromal cell bodies migrated close to and became oriented along the basal lamina. No interruptions were seen in the lamina densa or in the laminin-like immunoreactivity in the basal lamina. Thus, there were no direct morphologic interactions between epithelial and stromal cells induced by estrogen. Some of the stromal cells developed a dilated rough endoplasmic reticulum and some developed multiple elaborate processes within 41 hours after minipump implantation. Within 28 hours, nuclear hypertrophy had occurred in 15% of the epithelial cell layer. If interactions occur between stromal and epithelial cells, and morphologic evidence presented here suggests they do, then all such interactions are through an intact lamina densa-laminin layer, and any chemical mediators affecting cells on opposite sides of the lamina densa must migrate through it.
Steroids 1991 Mar
PMID:Rat endometrial stromal-epithelial response to estrogen infusion. 204 30

Glucose and steroids have been used in the treatment of children with Reye's syndrome, while carnitine and coenzyme Q10 have been the subject of some recent studies which suggest that these agents may have a role in the treatment of Reye's syndrome and Reye-like syndrome due to margosa oil poisoning. Because of the paucity of causes of Reye's syndrome seen at any one centre, the clinical variability of the disease, and limited knowledge of definite aetiologic factors, controlled clinical trials are not easy to carry out or to interpret in human cases. These caveats were overcome by evaluation of these four treatment modalities in an established margosa-oil-induced animal model of Reye's syndrome. Effectiveness of the treatment modalities was determined from clinical response and histopathologic parameters (grading of light microscopic fatty changes and ultrastructural changes in the hepatocytes). Results show that carnitine per se produces a small improvement in survival, but statistically, more significant benefit is seen with glucose administration. Carnitine plus 10% dextrose appears to produce better results. Evaluation of coenzyme Q10 and carnitine on histopathologic parameters in the liver after a sublethal dose of margosa oil showed no obvious ameliorating effect on liver pathology. Steroids (dexamethasone/methylprednisolone) had no beneficial effects in reducing mortality, affecting glycogen storage or lipid accumulation. Changes in the mitochondria, ribosomes and endoplasmic reticulum were unaltered from the groups treated with margosa oil alone. While glucose and carnitine supplements appear to be beneficial, the other modes of therapy do not seem to hold much promise in the treatment of Reye-like syndrome in the margosa-oil-induced animal model.
 ...
PMID:Evaluation of the possible role of glucose, carnitine, coenzyme Q10 and steroids in the treatment of Reye's syndrome using the margosa oil animal model. 228 30

The present in vitro studies using interstitial cells of adult rat testes demonstrated that ethanol inhibits LH- and 8-bromo-cyclic AMP-stimulated testosterone synthesis, pregnenolone- and progesterone-stimulated testosterone synthesis, and basal testosterone synthesis. However, the patterns of inhibition following exposure to 0.22 to 880 or 1100 mM ethanol were different. In general, the inhibition curves for LH-, 8-bromo-cyclic AMP-, pregnenolone- and progesterone-stimulated testosterone synthesis were biphasic, with a gradual slope from 0.22 to 220 mM ethanol, and a sharper slope with concentrations of ethanol greater than 220 mM. Basal testosterone synthesis was reduced only to 74% of control with ethanol concentrations up to 44 mM, and higher concentrations of ethanol reduced testosterone synthesis no further. The effect of ethanol on Lh-stimulated cyclic AMP accumulation showed an even different pattern: some of the lower concentrations of ethanol inhibited cyclic AMP accumulation, while higher levels of ethanol progressively increased cyclic AMP accumulation. These studies demonstrate that isolated interstitial cells are highly sensitive to the direct effects of ethanol; they also suggest that the principle site of ethanol inhibition may be at the level of the smooth endoplasmic reticulum where progesterone is converted to testosterone.
Steroids 1980 Nov
PMID:Direct inhibition of testosterone synthesis in rat testis interstitial cells by ethanol: possible sites of action. 625 26

In anterior pituitaries from male rats, it appeared that 5 alpha-androstane-3 beta,17 beta-diol was quickly metabolized into 5 alpha-androstane-3 beta,6 alpha-17 beta-triol and 5 alpha-androstane-3 beta,7 alpha,17 beta-triol by action of 6 alpha- and 7 alpha-hydroxylases. Hydroxysteroid hydroxylases were located in endoplasmic reticulum and were dependent on NADPH+. Their optimum pH was 8.0, optima temperature, 37 degrees C, and their apparent Km was 2.7 microM. Hydroxylative reactions were not reversible and not modified by gonadectomy. Hydroxylation seemed an efficient control of the pituitary level of 5 alpha-androstane-3 beta,17 beta-diol.
Steroids 1982 Dec
PMID:Studies on the 5 alpha-androstane-3 beta,17 beta-diol-6 alpha-hydroxylase and on the 5 alpha-androstane-3 beta,17 beta-diol-7 alpha-hydroxylase in anterior hypophysis of male rats. 718 13

Over 400 P450s have been identified to date in prokaryotes and eukaryotes, plants and animals, mitochondria and endoplasmic reticulum. These enzymes function in areas such as metabolism and steroidogenesis. The eukaryotic members of this gene superfamily of proteins have proved difficult to study because of the hydrophobic nature of their substrates, their various redox partners, and membrane association. To better understand the structure/function relationship of P450s-what determines substrate specificity and selectivity, what determines redox-partner binding, and which regions are involved in membrane binding-we have compared the three crystallized, soluble bacterial P450s (two class I and one class II) and a model of a steroidogenic, eukaryotic P450 (P450arom), to define which structural elements form a conserved structural fold for P450s, what determines specificity of substrate binding and redox-partner binding, and which regions are potentially involved in membrane association. We believe that there is a conserved structural fold for all P450s that can be used to model those P450s that prove intransigent to structural determination. However, although there appears to be a conserved structural core among P450s, there is sufficient sequence variability that no two P450s are structurally identical. NADPH-P450 reductase transfers electrons from NADPH to P450 during the P450 catalytic cycle. This enzyme has usually been thought of as a simple globular protein; however, sequence analysis has shown that NADPH-P450 reductase is related to two separate flavoprotein families, ferredoxin nucleotide reductase (FNR) and flavodoxin. Recent studies by Wolff and his colleagues have shown that the FAD-binding FNR domain and FMN-binding flavodoxin domain of human NADPH-P450 reductase can be independently expressed in Escherichia coli. The subdomains can be used to reconstitute, however poorly, the monooxygenase activity of the P450 system. We have been utilizing the reductase domain of P450BM-3 to study the mechanism of electron transfer from NADPH to P450 in this complex multidomain protein. We have overexpressed both the FNR subdomain and the flavodoxin subdomain in E. coli and fully reconstituted the cytochrome c reductase activity of this enzyme. Our studies have shown that electron transfer from NADPH through the reductase domain to the P450 requires shuttling of the FMN subdomain between the reductase subdomain and the P450. Studies of the factors that control the molecular recognition and interaction among these three proteins are complicated by the weakness of the association and changes in the strength of the interaction depending on the redox state of each of the components. How these structural and mechanistic studies of a soluble bacterial P450 can be extended to gain a better understanding of the control of membrane-bound eukaryotic P450-dependent redox systems is discussed.
Steroids 1997 Jan
PMID:P450BM-3; a tale of two domains--or is it three? 902 25

Principal cells show marked structural differences in the proximal, middle, and distal regions of the vas deferens, reflective of diverse functional activities. In the present study, we performed electron microscopy to examine the structural features of principal cells using glutaraldehyde-fixed, Epon-embedded material, while functional parameters were examined using light microscopic immunocytochemistry on Bouin-fixed, paraffin-embedded material. In the proximal region, the cuboidal principal cells resembled those of the cauda epididymidis, but few clear cells and occasional narrow cells were present. In the middle region, principal cells often contained blebs of their apical cytoplasm containing vesicular and tubular profiles. These blebs extended far from the cell surface and appeared to be liberated into the lumen, suggesting an apocrine type of secretion. In the distal region, dilated intercellular spaces containing numerous membranous profiles of different shapes and sizes were noted between adjacent principal cells and overlying basal cells. The use of an anti-aquaporin-1 antibody revealed an intense reaction over the endothelial cells of numerous vascular channels in the lamina propria. Taken together, these observations suggested water transport from the lumen of the vas deferens via the dilated spaces to underlying vascular channels, the function of which may be to concentrate sperm. The infranuclear cytoplasm of principal cells of this region showed whorls of smooth endoplasmic reticulum (sER). Large intracytoplasmic cavities were found within the sER aggregates, and these contained membranous profiles that appeared to peel off from the surrounding sER elements. Various images of such cavities closely juxtaposed to the lateral plasma membrane suggested that the membranous profiles of the intercellular spaces were derived from them. Use of anti-3beta-hydroxysteroid dehydrogenase antibody revealed an intense reaction over principal cells of the vas deferens, as well as over the blebs in the lumen of the vas deferens, which is indicative of the steroid synthesis performed by these cells. The release of sER membranous profiles into the dilated spaces and the presence of blebs in the lumen may represent a means of transporting steroids that are destined for different sites out of the principal cells. Steroids in the blebs would be ultimately destined for utilization by luminal sperm, while those steroids in the dilated spaces are designed for utilization by muscle layers of the lamina propria. In summary, principal cells of the vas deferens appear to be involved in synthesis and secretion of steroids and in eliminating water from the lumen of the vas deferens.
 ...
PMID:Principal cells of the vas deferens are involved in water transport and steroid synthesis in the adult rat. 1010 Apr 86

Previous work from our laboratory demonstrated that 1,25(OH)2D3 rapidly stimulated hydrolysis of membrane polyphosphoinositides (PI) in rat colonocytes and in Caco-2 cells, generating the second messengers DAG and IP3. [Ca2+]i subsequently increased due to IP3-mediated release of intracellular Ca2+ stores, and to Ca2+ influx through a receptor-mediated Ca channel. Studies examining purified antipodal plasma membranes and experiments using Caco-2 cell monolayers found that 1,25(OH)2D3 influenced PI turnover only in the basolateral (BLM) and not brush border (BBM) membranes. Vitamin D analogues with poor affinity for the vitamin D receptor were found to effectively stimulate PI turnover, suggesting the presence of a unique vitamin D receptor in the BLM. Studies from our laboratory have demonstrated saturable, reversible binding of 1,25(OH)2 D3 to colonocyte BLM. Recently, we found that 1,25(OH)2D3 activated the tyrosine kinase c-src in colonocyte BLM by a heterotrimeric guanine nucleotide binding protein (G-protein)-dependent mechanism, with subsequent phosphorylation, translocation to the BLM, and activation of PI-specific phospholipase C gamma. Due to the rise in [Ca2+]i and DAG, two isoforms of protein kinase C (PKCalpha and PKCbeta2), but not other isoforms were activated by 1,25(OH)2D3 in rat colonocytes. Recent studies demonstrated that the seco-steroid translocated the beta2 isoform to the BLM, but not the BBM. In contrast, the alpha isoform did not translocate to either antipodal plasma membrane, but modulated IP3-mediated Ca2+ release from the endoplasmic reticulum. Preliminary studies have shown that 1,25(OH)2D3 also activated phosphatidylcholine phospholipase D (PLD) in Caco-2 cells, generating phosphatidic acid and contributing to the sustained rise in DAG. PLD stimulation occurred by both PKC-dependent and -independent mechanisms. Inhibitors of G-proteins, c-src, and PKC blunted the seco-steroid-mediated activation of PLD. Cells stably transfected with sense PKCalpha showed increased 1,25(OH)2D3-stimulated PLD activation, whereas transfectants with antisense PKCalpha had an attenuated response. In addition, 1,25(OH)2D3 also regulated PLD by activating the monomeric G-protein rho A by a mechanism independent of the G-protein/ c-src/PKC pathway.
Steroids
PMID:Rapid effects of 1,25(OH)2 vitamin D3 on signal transduction systems in colonic cells. 1032 82


1 2 3 4 Next >>