Leydig cells from mature rat testes contain high levels of 11 beta-hydroxysteroid dehydrogenase (11HSD), an enzyme that oxidatively inactivates glucocorticoids. We have proposed that the 11HSD of Leydig cells protects the testis from the effects of high levels of glucocorticoids, as may occur in stress and Cushing's disease. In this paper we investigate whether testicular 11HSD by inactivating glucocorticoids diminishes their ability to inhibit testosterone (T) production. Corticosterone (B) and dexamethasone (DEX) inhibited T production by purified Leydig cells in a dose-dependent manner. Activity was diminished by 50% with 1.5 nM DEX vs. 0.4 microM B. The shapes of the inhibition curves were consistent with a saturable process; inhibition by both steroids was overcome with the glucocorticoid receptor antagonist RU486. We concluded that the effect was mediated by glucocorticoid receptors. Aldosterone, 11 beta-hydroxyprogesterone, and 11-deoxycorticosterone did not decrease T production. The greater potency of DEX compared to B may be due to its resistance to oxidative inactivation by 11HSD. As 11-dehydrocorticosterone, the product of the oxidation of B by 11HSD, did not inhibit T production, it was predicted that inactivation of 11HSD should enhance the inhibitory effect of B. Consistent with this prediction, inhibition by B was increased by carbenoxolone, an inhibitor of 11HSD, becoming more similar to that by DEX. Suppression of T production by DEX (which is not a substrate of 11HSD) was unaffected by carbenoxolone. We conclude that through reduction of the levels of inhibitory glucocorticoids, 11HSD has a novel role among Leydig cell steroid-metabolizing enzymes in the regulation of T production.
We have proposed that the 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) of Leydig cells protects against glucocorticoid-induced inhibition of testosterone (T) production. However, Leydig cells express type I 11 beta-HSD, which has been shown to be reductive in liver parenchymal cells. Because reduction would have the opposite effect of activating glucocorticoid, the present study was designed to determine: 1) whether Leydig cell 11 beta-HSD is primarily oxidative or reductive; and 2) whether oxidative and reductive activities are separately modified by known regulators of Leydig cell steroidogenic function. Leydig cells and liver parenchymal cells were purified from mature male Sprague-Dawley rats (250 g BW), and 11 beta-HSD oxidative and reductive activities were measured using radiolabeled substrates and TLC of triplicate media samples from 1-h incubations immediately after cell isolation. Enzyme activities also were examined in purified Leydig cells at the end of 3 days of culture in vitro in the presence of LH (10 ng/ml), dexamethasone (DEX, 100 nM), T (50 nM), or epidermal growth factor (EGF, 50 ng/ml). In confirmation of previous reports, the reductive activity of 11 beta-HSD was predominant over oxidation in liver parenchymal cells. In contrast, 11 beta-HSD oxidative activity prevailed over reduction in Leydig cells by a ratio of 2:1. The activities of 11 beta-HSD also were analyzed in Leydig cells that were purified 7 days after endogenous glucocorticoid levels were suppressed by adrenalectomy (ADX). Oxidative activity declined in Leydig cells after ADX (22.53 +/- 1.12 pmol/h.10(6) cells, mean +/- SEM vs. 31.47 +/- 1.48 pmol/.10(6) cells in sham-operated controls, P < 0.05), whereas there was no change in reductive activity. This indicated that physiologically active corticosterone is involved in maintaining the predominance of 11 beta-HSD oxidation. When enzyme activities were analyzed in Leydig cells after 3 days of hormonal treatment in vitro, oxidation and reduction were observed to change in opposing directions. Culture of Leydig cells from sham-operated control rats with either LH, T, or EGF resulted in declines in oxidative activity from 33.35 +/- 0.77 to 28.24 +/- 1.93, 27.30 +/- 0.96, and 24.13 +/- 1.02 pmol/ h.10(6) cells (x +/- SE), respectively. However, EGF stimulated 11 beta-HSD reductive activity in cultured Leydig cells from both control (from 18.97 +/- 1.10 to 27.16 +/- 0.71 pmol/h.10(6) cells and ADX rats (from 16.51 +/- 0.75 to 23.56 +/- 0.84 pmol/h.10(6) cells). Among the hormonal treatments, only DEX increased oxidative activity and simultaneously decreased reductive activity in Leydig cells from ADX rats. This increase accentuated the predominance of oxidative activity in Leydig cells, with a ratio of oxidative to reductive activity of 4:1 after DEX treatment, compared with 2:1 in controls that were untreated. We conclude that 11 beta-HSD activity in Leydig cells is primarily oxidative. Moreover, oxidation and reduction are regulated separately by hormones.
The estrogen and progesterone receptors of several organs of the prenatal cynomolgus macaque and the fetal mouse were studied using a combination of the dextran-coated charcoal technique and high-performance liquid chromatography. This procedure permitted the concurrent measurement of both receptors in minute amounts of tissue. Estrogen receptors, but not progesterone receptors, were found in the fetal monkey and mouse uteri. No estrogen or progesterone receptors were detected in the lungs, liver, kidney, heart, brain, adrenal gland, or limbs of mouse or monkey fetuses. The nonspecific binding of radioactive ORG-2058 was not displaced by unlabeled progesterone, 17 alpha-hydroxyprogesterone caproate, or ORG-2058. Because the steroid receptors that are indispensable mediators of steroid hormone action were absent from the nonreproductive tissues, prenatal development of these organs and tissues cannot be adversely influenced by exposure to estradiol, progesterone, or their synthetic analogues.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.