Showing papers on "Steroid biosynthesis published in 1981"

Role of follicle wall in meiosis reinitiation induced by insulin in Rana pipiens oocytes.

Abstract: The involvement of the ovarian follicle wall in insulin induction of Rana pipiens oocyte maturation in vitro was examined. Complete removal of the follicle wall significantly decreased, but did not obliterate, oocyte maturation (i.e., germinal vesicle breakdown, GVBD) induced by insulin. Dose-response studies of GVBD induction revealed that oocytes within intact follicles were at least 100 times more sensitive to insulin than denuded oocytes. Addition of cyanoketone, a steroid biosynthesis inhibitor, to intact follicles also suppressed insulin-induced GVBD. Inhibitory effects of either follicle wall removal or cyanoketone were not observed when denuded oocytes were treated with progesterone. Addition of either progesterone or pregnenolone to insulin-treated denuded oocytes augmented the oocyte GVBD response compared to either steroid alone and essentially replaced the effect of the follicle wall. In summary, steroidogenesis in the follicle wall appears to be a major factor contributing to the ability of insulin to induce GVBD. However, whether insulin stimulates follicle wall steroidogenesis or simply augments the biological activity of endogenous basal steroid levels is unresolved. The in vitro results show that oocyte maturation can be modulated by the combined actions of several hormones. Such steroid-insulin interactions may also be relevant to understanding the control of oocyte maturation in amphibians and other vertebrates, including mammals, under physiological conditions in vivo.

Hormonal and cellular interactions in follicular steroid biosynthesis by the sheep ovary.

Abstract: Studies of isolated cell types from sheep follicles revealed several functional changes which occur during follicular maturation. Cyclic AMP production by granulosa cells from the smallest follicles studied (1-3 mm diameter) was stimulated by FSH but not by hCG, suggesting functional FSH receptors at this early stage of differentiation. Medium-sized follicles (4-6 mm) responded to both FSH and hCG. Granulosa cells were unable to synthesize androgens, but readily converted exogenous testosterone to oestradiol-17 beta. This conversion occurred to a limited extent in the cells from the smallest follicles, but was much greater in medium and large (greater than 6 mm) follicles. Oestradiol production by theca preparations from small follicles was barely detectable, but increased markedly with increasing follicle size. Androgen (androstenedione and testosterone) production by theca preparations was stimulated by hCG. This stimulation was short-lived, and levels declined to below control values after 6 h of culture. This decline could not be prevented by addition of cyclic AMP. The presence of granulosa cells with thecal preparations (i.e. follicle wall tissue) enhanced production of androgen by the theca, the effect being more marked for testosterone than for androstenedione. In-vivo studies in which granulosa cells and follicular fluid were removed during the preovulatory period suggested that granulosa cells and/or follicular fluid contributed to the oestradiol secreted into the ovarian vein during this period, but did not exclude a significant contribution by the theca as well.

Prolactin Stimulation of Testicular Steroid Biosynthesis in the Male Rat

Abstract: The effect of prolactin on testicular steroidogenesis was studied in intact adult male rats and in animals treated for 12 days with the LHRH-agonist [D-Ala6, des-Gly-NH210]LHRH ethylamide (LHRH-agonist, 1 μg every third day). Testicular LH and prolactin receptors are decreased to 20 and 50% of control, respectively, 26 hours after the last injection of LHRH-agonist. This loss of testicular receptors is accompanied by an increase in the concentration of testicular pregnenolone (500%) and progesterone (700%), whereas 17-OH-progesterone, androstenedione, testosterone, and dihydrotestosterone are decreased to 50, 25, 10, and 60% of control levels, respectively. The Injection of 2 mg of ovine prolactin in intact rats 2 hours before sacrifice leads to an increase in testicular 17-OH-progesterone (300%) and androgen (100%) levels. However, in animals treated with the LHRH-agonist, prolactin injection leads to an increase in only progesterone and pregnenolone levels, whereas the concentration of the other steroids remains low. The present data indicate that the stimulatory effect of prolactin at an early stage(s) of the testicular steroidogenic pathway remains relatively intact In the desensitized testis and leads to an apparent accentuation of the LHRH-agonist-lnduced enzymatic blockage at the level of 17-hydroxylase and 17, 20-desmolase activities.

452 DIRECT DETERMINATION OF 17α-HYDROXYLASE (170Hase) DEFICIENCY IN A MALE PSEUDOHERMAPHRODITE BY IN VITRO STUDIES OF TESTICULAR STEROID BIOSYNTHESIS

Abstract: A 4 year old male (46XY) pseudohermaphrodite with 170Hase deficiency (Ped.Res.13:387A,1979) underwent bilateral orchiectomy 2 days after 3 days of HCG (2,000 u/day IM), during which serum levels of testosterone, dihydrotestosterone,androstenedione, 170H-progesterone (170HP) and estradiol did not increase while progesterone increased from 52 to 69 ng/dl. Teased testicular tissue was incubated with 10uCi (3.3 nmol) of 3H-pregnenolone or 3H-170HP in 3 ml NADP fortified KRB buffer, pH 7.4, for 3 hr. at 37°C with and without 100 IU/ml HCG. Thus the testes of this patient were unable to metabolize pregnenolone, but were able to metabolize 170HP. The data are consistent with deficiency of 170Hase activity.

Hormones and evolution: introduction

Abstract: Publisher Summary This chapter discusses the evolution of hormones in vertebrates and invertebrates. Most invertebrate neurosecretory hormones are specific for a certain phylum or even species and most vertebrate hormones can only be detected among vertebrates. In some vertebrate hormones, there is evidence for cladogenetic evolutionary trends; however, on the whole, these trends are minor. It seems that each phylum selected certain substances as chemical messengers and neither the chemical evolution of the messenger nor the evolution of the messenger's physiological action can be traced. Thus, the maturation-inducing hormone of echinoderms, 1-methyladenine, has no known physiological action in any other phyla. Similarly, the parent molecule of ACTH + LPH or, for that matter, the fragments of this molecule, ACTH, LPH, and alpha- and beta-MSH are not substances that are elaborated by different phyla and having different actions in different phyla. They are exclusively vertebrate hormones. However, with steroids, the situation is different. It seems quite plausible that coding for steroid biosynthesis/metabolism is a part of the eukaryotic genome, irrespective of evolutionary ranking.

Tumour steroid hormone synthesis and estrogen receptor status in breast cancer patients.

Abstract: The capacity of breast cancer to synthesise active androgens and estrogens has been related to estrogen receptor (ER) status in 79 postmenopausal patients with breast cancer. Although there was no quantitative relationship between levels of ER and steroid metabolism in ER positive tumours, there was (a) a positive correlation between estrogen synthesis and ER positivity and (b) increased androgen synthesis and ER negativity. This may imply an inherent difference in the handling of hormones in ER positive and negative tumours.