Showing papers on "Steroid biosynthesis published in 1977"

A study of the effects of methyl mercury, cadmium, arsenic, selenium, and a PCB, (Aroclor 1254) on adrenal and testicular steroidogeneses in vitro, by the gray seal Halichoerus grypus.

Abstract: An in vitro study on the effects of the contaminants polychlorinated biphenyl (Aroclor 1254) (PCB), methyl mercury (MeHg), arsenic (As), cadmium (Cd), and selenium (Se) on the biosynthesis of steroid hormones in the gray seal (Halichoerus grypus) indicated altered steroid biosynthesis. Biotransformed delta4-androstene-3, 17-dione (delta 4A), dehydroepiandrosterone, 11-ketotestosterone (11-KT), and testosterone (T) were detected in all seal testicular incubates. Yields of 11-KT were greatly increased in the presence of Aroclor 1254. All contaminants except As and Se stimulated the in vitro biosyntheses of T, with the greatest increase in production of T being in the Cd-treated tissue. Cortisol (F), corticosterone (B), aldosterone (ALDO) but no cortisone (E), were biosynthesized by the seal adrenal tissue. Corticosterone (B) was the principal transformation product in all incubations with less B produced by the treated adrenals than by the control. The lowest yeild of B was achieved by the Se-treated adrenal. The yeild of ALDO was also lower in all contaminant treated incubations, with Se and Cd giving the greatest inhibition. More F was biosynthesized by all the treated adrenals than by the control. The greatest increase of production of F(6-fold) from progesterone was by the As-treated adrenal.

Comparative physiology of the renin-angiotensin system.

Abstract: Renin or a renin-like substance is found in the kidneys of many vertebrate species. It is absent from the kidneys of cyclostomes and elasmobranchs and first appears in holosteans and the bony fishes as well as in all higher vertebrate species. Juxtaglomerular cell granules also appear first in holosteans and the bony fishes while the macula densa first appears in amphibians. In telecost fishes, the corpuscles of Stannius contain Bowie-stainable granules and a renin-like pressor substance. Among classes and, in some cases, species of vertebrates, specificity in the reaction of renin with a substrate has been demonstrated. There is also some species and class variation in the angiotensin molecule since angiotensins of fishes, amphibians, reptiles and birds have chemical characteristics different from each other and from those of ammmals. A role for renin in stimulating interrenal gland steroid biosynthesis and in influencing water and ion regulation in nonmammalian vertebrates is discussed.

Production and Metabolism of Progesterone and Androstenedione by Cultured Mouse Blastocysts

Abstract: A study designed to determine the point at which mouse embryo is 1st capable of producing progesterone and androstenedione is presented. Mouse preimplantation embryo and postblastocyst cultures were assayed by radioimmunoassay and thin-layer chromatography. Evidence of progesterone formation in the first 48 hours of culture was absent. A small amount of progesterone production was detected between the 6th-7th equivalent gestation days (EGD). By the 8th-9th EGD a peak production of .53 p mole/blastocyst/day was reached. After the blastocyst has attached to the surface of the dish and trophoblastic outgrowth has taken place progesterone is produced. These results were confirmed by chromatographic analysis and permeability studies. The ability of blastocyst and postblastocyst cultures to produce and metabolize androstenedione was also studied. Postblastocyst cultures were found to convert dehydroepiandrosterone (DHEA) to androstenedione. These results suggest that delta (5) 3beta hydroxysteroid dehydrogenase activity (3beta-HSD) needed to convert DHEA to androstenedione and other enzyme activities involved in the metabolism of progestin and androgen are only acquired by postimplantation conceptuses. This would negate the possibility that steroid biosynthesis by the mouse blastocyst is involved in its implantation.

Stimulation of corticosteroid biosynthesis by angiotensin I [des-asp1]angiotensin I, angiotensin II and [des-asp1]-angiotensin II in bovine adrenal fasciculata cells.

Abstract: The effect of angiotensin I (AI), angiotensin II (All), [des-asp1]AI, [des-asp1]AII and [des-asp1-arg2]AII on corticosteroid production in isolated fasciculata cells from bovine adrenals has been studied. All and [des-asp1]AII in concentrations ranging from 10−9M to 10−6M had a potent stimulatory effect on steroid biosynthesis. The dose-response curves for both peptides were identical. AI was about 3 times less potent than All and [des-asp1]AII. The effect of AI was not due to its conversion to All. [des-asp1]AI was as active as AI. No significant conversion to [des-asp1]AII was observed. [des-asp1-arg2]AII had only a minimal effect on steroidogenesis. The structural analog [sar1,-ala8]AII inhibited all angiotensins specifically and competitively. The affinity of the cellular binding site was higher for All and [des-asp1]AII than for [sar1ala8]AII, but lower for AI and [des-asp1]AI than for the inhibitor. Combination of submaximal doses of AI and All resulted in an additive effect on steroid production. B...

Ultrastructural evidence for the existence of steroid synthesizing cells in the ovary of the starfish, Asterias rubens (Echinodermata)

Abstract: The ultrastructure of cells showing characteristic features of steroid producing cells in the ovaries of the starfish, Asterias rubens, is described. The correlation between the appearance of these cells and steroid biosynthesis in ovarian tissue of A. rubens is discussed. The importance of the discovery of these cells in view of the biosynthesis of steroids and the phylogeny of Echinodermata is mentioned.

Histochemical localization of 3 beta-hydroxysteroid dehydrogenase in the testes of chicken-pheasant hybrids.

Abstract: Histochemical studies on the activity of 3β-hydroxysteroid dehydrogenase (3β-HSD) in the testes of adult chicken-pheasant hybrids and domestic fowl of similar age were carried out using dehydroepiandrosterone as the substrate. The reaction for 3β-HSD was positive in the interstitial tissue and negative within seminiferous tubules of domestic fowl. In chicken-pheasant hybrids, a strong positive reaction for 3β-HSD was observed in the interstitial tissue and within the seminiferous tubules suggesting that, in hybrid testes, both Leydig cells and cells of seminiferous tubules may be capable of steroid biosynthesis. Since the plasma testosterone levels in these birds were found to be extremely low, it is hypothesized that either the chicken-pheasant hybrids do not release testosterone in sufficient amounts in the circulation or the type of steroid produced by the 3βHSD-positive cells may be different from testosterone that is required for the maintenance of normal fertility and the development of secondary sexual characteristics.

Steroid biosynthesis by gonads of rats submitted to chronic hypobaric hypoxia.

Abstract: In vitro biosynthesis of steroids by testes and ovaries was studied in rats submitted to 6,000 m simulated altitude for 23 weeks and their controls at sea level atmospheric pressure. Gonads' homogenates were incubated in the presence of 4(-14) C-pregnenolone and cofactors. Extractions, partitions, paper chromatography and finally crystallizations until constant specific activity were performed. Tritium labelled internal standards were used to correct for methodological losses. In male animals, only androstenedione biosynthesis calculated per rat as well as the weight of the testes were reduced in hypoxia. Nevertheless, this reduction was accompanied by an equivalent decrease in body weight; testosterone biosynthesis was not significantly changed. On the contrary, in females, estradiol biosynthesis and the weight of the ovaries were significantly higher in hypoxic than in control animals. Macroscopic and microscopic aspect of the ovaries in hypoxic rats also indicate a hyperactivity of the steroidogenic function. Weight curves and mortality studies confirmed previous findings about the advantage of females in adaptation to hypoxia. Results show that ovaries play an active role in this process.

Changes in steroid biosynthesis by adrenal homogenates of the possum (Trichosurus vulpecula) at various stages of sexual maturation with special reference to 5β-reductase activity

Abstract: 1. 1. A marked difference was found in the yields of 11β-hydroxylated and 5β-reduced products from 14C progesterone by adrenal homogenates of immature and adult possums. 2. 2. From adrenals of immature possums and possums in early stages of gonadal activity (ages 5–18 months) the yields of conversion products were; cortisol 52.4 ± 2.4% , corticosterone 16.3 ± 2.2% , total 5β-reduced products 9.6 ± 3.4% (mean ± S.E.M.) . In yields aldosterone, 21-deoxycortisol, 11β- and 17α-hydroxyprogesterone. 3. 3. The yields of products from adrenals of young sexually mature possums (ages 15–24 months) were variable. From five the levels were similar to that of immature animals. From four there was an increase in the yields of 5β reduced products (of varying degrees) with a concomitant fall in unreduced products, the average yields being; cortisol 12%, corticosterone 3% and total 5β-reduced metabolites 60%. 4. 4. The yields of conversion products from adrenals of adults ( > 2 1 2 years old) were cortisol 1.3 ± 0.8% and total 5β-reduced-11-deoxy-steroids 71 ± 8% (mean ± S.E.M.) . 5. 5. The similarities of the changes in adrenal 5β-reductase activity in the possum and guinea pigs at different stages of development are discussed.