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)

A simple method is described for the simultaneous radioligand assay of four delta5-3beta-hydroxysteroids adjacent to one another on the biosynthetic pathway (pregnenolone [1], 17alpha-hydroxypregnenolone, dehydroepiandrosterone and 5-androsterone-3beta, 17beta-diol), and their four delta4-3keto products (progesterone, 17alpha-hydroxyprogesterone, 4-androstene-3, 17-dione and testosterone). Two plasma aliquots are extracted and fractionated each for four steroids and individual corrections are made for losses. For fractionation, maximum use is made of the high resolution and reproducibility of celite minicolumns, using propylene glycol as stationary phase, and a discontinuous gradient of ethyl acetate in iso-octane as mobile phase. The fractions are then assayed in the appropriate radioligand end-assay system. Each assay was finally validated by demonstrating coincidence of peaks of immuno- and radioactive steroid in extracts of female plasma. Results in pre-pubertal girls and women in the follicular phase of the menstrual cycle suggest that the major change in adrenal steroid production at puberty may be an increase in 17, 20-desmolase activity. There appears to be little reversal of this change in adrenal function after ovariectomy.
Steroids 1976 Aug
PMID:A simple method for the assay of eight steroids in small volumes of plasma. 97 34

Testicular homogenates of tamoxifen-treated rats were incubated with labeled steroid precursors (progesterone, 17 alpha-hydroxyprogesterone, dehydroepiandrosterone, androstenedione or testosterone) in order to study the effect of tamoxifen on testicular steroidogenesis. The results indicate that a 9 day treatment with a daily dose of 1 mg tamoxifen produces a reduction of the synthesis of testosterone. Inhibition of the 17 alpha-hydroxylase and C17,20-desmolase enzyme systems was observed together with an increased 20 alpha-hydroxysteroid dehydrogenase activity.
Steroids 1989 Jun
PMID:Effect of tamoxifen on the activity of enzymes of testicular steroidogenesis. 253 Jun 60

In an attempt to confirm where in the testosterone (T) biosynthetic pathway of the rat testis ketoconazole (KTZ) inhibits T production, rat testicular mince was incubated with either 10 micrograms/ml or 100 micrograms/ml KTZ in the presence and absence of hCG (1 IU), and intratesticular pregnenolone (delta 5P), progesterone (P), 17-alpha-hydroxyprogesterone (17 alpha-HP), androstenedione (A) and testosterone (T) were assayed. In the absence of hCG, 10 micrograms/ml KTZ was sufficient to reduce intratesticular T by 80%. At this concentration of KTZ, intratesticular 17 alpha-HP (ng/g testis, mean +/- SEM) increased from 0.3 +/- 0.1 to 1.3 +/- 0.2 (p less than 0.0025), whereas intratesticular A decreased from 84 +/- 7 to 17 +/- 1 (p less than 0.005). KTZ did not inhibit the conversion of P to 17 alpha-HP. From these data it was concluded that KTZ has its inhibitory effect on testosterone biosynthesis in the rat testis primarily at the step catalyzed by the 17,20 desmolase enzyme.
Steroids
PMID:Effect of in vitro ketoconazole on steroid production in rat testis. 383 56

Ketoconazole (K) is an antifungal imidazole derivative which has been shown to be a potent inhibitor of testosterone (T) biosynthesis in rodents and humans. To study the effect of K on rat testicular steroidogenesis we measured the activities of five testicular microsomal steroidogenic enzymes in K-treated rats and controls. Thirty male adult rats were given either 2 mg K or water every 12 hours by mouth during 5 days. Mean testicular weight was similar in both groups of animals. The K-treated group had a T serum concentration of 83 +/- 14 ng/dL whereas it was 94 +/- 16 ng/dL in the control group (NS). The K-treated animals had decreased activities of the 3 beta-hydroxysteroid dehydrogenase (830 +/- 48 vs 2,245 +/- 109 pmol/mg protein/min, P less than 0.001), 17-hydroxylase (243 +/- 5 vs 676 +/- 17 pmol/mg protein/min, P less than 0.001), 17-ketosteroid reductase (31 +/- 2 vs 169 +/- 7 pmol/mg protein/min, P less than 0.001), and aromatase enzymes (92 +/- 6 vs 123 +/- 7 pmol/mg protein/min, P less than 0.01). The 17,20-desmolase activity was similar in both groups of animals (210 +/- 4 vs 171 +/- 18 pmol/mg protein/min). We conclude that K given orally to rats inhibits the activity of several testicular steroidogenic enzymes.
Steroids 1985 Jul
PMID:Effects of ketoconazole on rat testicular steroidogenic enzymatic activities. 387 79

Yolk free blastoderms of chick embryo were incubated 3 or 22 hours with labeled pregnenolone, progesterone, 17-hydroxyprogesterone, dehydroepiandrosterone, androstenedione, testosterone and estradiol-17 beta. Metabolites and unconverted substrates were found both in the incubation medium and in the cells. Enzymes responsible for identified conversions were: 17 alpha-hydroxylase, 17-20-desmolase, delta 5 3 beta- and 3 alpha-hydroxysteroid dehydrogenase, 17 beta-hydroxysteroid dehydrogenase and 5 alpha- and 5 beta-reductase. The results suggest that the steroid metabolizing enzyme activities found may reflect a more general ability of early embryonic cells.
Steroids 1984 Mar
PMID:Early steroid metabolism by chick blastoderm in vitro. 624 Aug 3

Parturition in the sheep is preceded by a complex series of changes in both fetal and maternal plasma-steroid hormone concentrations. Using the chronically catheterized fetal sheep preparation, we measured unconjugated and sulfoconjugated pregnenolone, 17 alpha-hydroxypregnenolone, dehydroepiandrosterone, and estrone in fetal and maternal plasma over the final 20 days before spontaneous vaginal delivery at term. Where appropriate, third degree polynomial functions were fitted to the changing plasma hormone concentration profile. Fetal and maternal plasma pregnenolone and pregnenolone sulfate both fell from maximum values in the last 4 days of gestation. Fetal and maternal plasma estrone and estrone sulfate concentrations underwent a terminal rise over the last 4 days of gestation that was a mirror image of the fall in plasma pregnenolone and pregnenolone sulfate. Maternal 17 alpha-hydroxypregnenolone rose over the last 4 days of gestation. Fetal 17 alpha-hydroxypregnenolone, maternal and fetal plasma dehydroepiandrosterone sulfate, and fetal plasma dehydroepiandrosterone sulfate, and fetal plasma dehydroepiandrosterone showed no trend during the period of study. Maternal plasma dehydroepiandrosterone rose over the last 4 days of gestation. These results support the view that increased activity of placental 17 alpha-hydroxylase and 17-20-desmolase is responsible for the conversion of C-21 steroids to estrogens at term. delta 5-Steroids are present in very high plasma concentrations in fetal sheep plasma and may constitute a more important precursor pool for estrogen biosynthesis than does circulating plasma progesterone.
 ...
PMID:Time trend analysis of plasma unconjugated and sulfoconjugated estrone and 3 beta-delta 5-steroids in fetal and maternal sheep plasma in relation to spontaneous parturition at term. 627 3

Interstitial cells derived from intact immature rats were cultured as monolayers. Their response to gonadotropins was evaluated by radioimmunoassay of 3',5'-cyclic AMP and steroids in the medium. Steroids were measured either directly (testosterone and progesterone) or after previous oxidation and thin layer chromatographic purification of the steroid extracts (4-androstene-3,17-dione, 5 alpha-androstane-3,17-dione, progesterone, 5 alpha-pregnane-3,20-dione). It could be demonstrated that these cells respond to gonadotropins with increased secretion of C19- and C21-steroids for at least 10 days. The total amount of steroids secreted in the medium, however, decreases markedly. During the first days of culture C19-steroid production falls dramatically whereas the secretion of C21 derivatives increases. A major fraction of the extracted steroids has undergone 5 alpha-reduction. A characteristic feature of cultured interstitial cells is the bell-shaped profile of the dose-response curve for gonadotropin stimulated androgen production. This profile is the result of a steroidogenic lesion situated at the level of the 17 alpha-hydroxylase and/or 17,20-desmolase and induced by high concentrations of gonadotropins. Daily changes with medium supplemented with LH or FSH, initiated on day 3 of culture, prevent a further loss of steroidogenic potential, restore the ability to produce C19-derivatives, and tend to normalize the dose-response curve for gonadotropin stimulated production of androgens.
 ...
PMID:Androgen and progestogen production in cultured interstitial cells derived from immature rat testis. 629 Jul 87

Decreased sperm counts and impaired sperm motility are present in a substantial proportion of men with varicocele. Elevations in the temperature of the affected testis, and increased spermatic vein estradiol (E2) concentrations have been found in some of these patients. To investigate the possibility that increases in temperature lead to a pattern of testicular steroidogenesis that results in increased E2 synthesis, we have examined the effects of temperature changes on the activities of four important testicular steroidogenic enzymes. 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), 17-hydroxylase (17-OH), 17,20-desmolase (17,20-D) and aromatase activities were measured in the microsomal fraction of rat, pig and horse testes. Incubations were performed at 34 degrees C, 36 degrees C, and 38 degrees C. The activities of all 4 enzymes increased with each 2 degrees C temperature elevation in roughly proportional amounts. We conclude that minor elevations in incubation temperature are associated with increases in the in vitro activity of four key testicular steroidogenic enzymes.
Steroids 1984 Mar
PMID:The effects of temperature on the activity of testicular steroidogenic enzymes. 633 11

Hyperprolactinemia has been associated with several reproductive disorders. To investigate whether hyperprolactinemia directly affects rat ovarian function, we examined the ovarian histopathology and the activities of the four ovarian enzymes 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), 17-hydroxylase (17-OH), 17,20-desmolase (17,20-D) and aromatase in hyperprolactinemic rats and controls. Hypophysectomized, gonadotropin-treated Fisher rats were made hyperprolactinemic by isografting pituitary glands under the kidney capsule. The control animals received skeletal muscle. The ovaries were resected, pooled according to prolactin levels and microsomal enzyme activities were measured from each pool. Prolactin (PRL) levels were 344 +/- 23 ng/ml in the hyperprolactinemic rats and 18 +/- 5 ng/ml in the controls (p less than 0.001). Estradiol concentrations were 609 +/- 47 pg/ml in the hyperprolactinemic animals and 56 +/- 13 pg/ml in the controls (p less than 0.001). Ovarian and uterine weights were significantly higher in the hyperprolactinemic rats (p less than 0.02). Ovarian histopathology demonstrated benign polycystic transformation in the hyperprolactinemic animals. Hyperprolactinemia had no effect on 3 beta-HSD, but was associated with significant decreases in the 17-OH, 17,20-D and aromatase activities when compared to controls (p less than 0.001). We conclude that prolactin has a direct effect on rat ovarian function which appears to be independent of changes in gonadotropin secretion.
Steroids 1984 Jun
PMID:The effects of prolactin on rat ovarian function. 633 28

The luteinizing hormone releasing hormone analog D-Trp6-Pro9-Net-LHRH (LHRHa) inhibits rat testicular testosterone secretion. To determine whether LHRHa decreases serum testosterone concentrations solely by inhibiting gonadotropin secretion or, in addition, by influencing directly testicular testosterone biosynthesis, we examined the effects of LHRHa on the activities of 5 key testicular steroidogenic enzymes. Thirty hypophysectomized, hOG treated rats were given either LHRHa (1 micrograms sc/day) or saline during 7 days. The LHRHa treated animals exhibited a significant decrease of serum testosterone when compared to the control group (498 +/- 37 ng/dl vs 2044 +/- 105 ng/dl, mean +/- SEM, P less than 0.001). 17-Hydroxyprogesterone serum levels were also decreased in the LHRHa treated rats (61 +/- 6 ng/dl vs 93 +/- 7 ng/dl, P less than 0.005), while serum progesterone levels were similar in both groups of animals. These changes in steroid concentrations were associated with decreases in the microsomal enzyme activities of 17-hydroxylase (37 +/- 9 vs 654 +/- 41 pmol/mg protein/min, P less than 0.001), 17,20-desmolase (103 +/- 9 vs 522 +/- 47 pmol/mg protein/min, P less than 0.001), 3 beta-hydroxysteroid dehydrogenase (1.7 +/- 0.02 vs 4.1 +/- 0.1 nmol/mg protein/min, P less than 0.001), aromatase (95 +/- 7 vs 228 +/- 6 pmol/mg protein/min, P less than 0.001) and 17-ketosteroid reductase (167 +/- 9 vs 290 +/- 18 pmol/mg protein/min, P less than 0.01) in the LHRHa treated animals. These findings indicate that LHRHa can inhibit directly rat testicular testosterone biosynthesis.
Steroids 1984 Feb
PMID:Direct effect of the luteinizing hormone releasing hormone analog D-Trp6-Pro9-Net-LHRH on rat testicular steroidogenesis. 639 51


1 2 3 4 Next >>