Regulation of Peptide Hormone Receptors and Gonadal Steroidogenesis

Effect of scrotal insulation on the pituitary--testicular axis of the ram

“…This aggregation effect will be less pronounced in the perfused tissue used in the present study as space left after shrinkage of the seminiferous epithelium is partly accounted for by the dilated lymphatics. Kerr, Rich & de Kretser (1979) have confirmed the impressions of earlier workers (Hanes, 1911;Lynch & Scott, 1951) (Chemes, Ri varóla & Bergada, 1976;Christensen & Peacock, 1980 (Schanbacher, 1979a;1980 (Schanbacher, 1979b;D'Occhio, Schanbacher & Kinder, 1982 (Catt et al, 1980) and an LHRH-like factor produced by the seminiferous tubule (Sharpe, Fraser, Cooper & Rommerts, 1981) have been shown to exert an intratesticular control of Leydig cell steroidogenesis, the relationship between these substances and Leydig cell structure and function has not yet been investigated. The role of the seminiferous epithelium in exerting some control of Leydig cell activity has been emphasized by Ucci (1982), who showed that there was an inverse relationship between Leydig cell size and activity, and germ cell maturation in the normal urodele testis.…”

Presence of specific growth hormone binding sites in rainbow trout (Oncorhynchus mykiss) tissues: Characterization of the hepatic receptor

“…Similar phenomena have been noted for GH/receptor binding in rabbit (Gerasimo et al, 1979). Such nonreversible binding of the hormone to its receptor might correspond to a first step of the internalization process as was found in human chorionic gonadotrophin-receptor interaction (Catt et al, 1980).…”

Mechanisms subserving the trophic actions of insulin on ovarian cells. In vitro studies using swine granulosa cells

“…The time course of insulin action and the susceptibility of insulin's effects to inhibitors of protein and RNA synthesis, suggest that insulin exerts important facilitative or trophic effects on one or more steps in the steroidogenic pathway of ovarian cells. This inference is congruent with the capacity of insulin to augment granulosa-cell production of progesterone, as well as its precursor, pregnenolone, and progesterone's major metabolite, 20a-hydroxypregn- distinctly separable initial mechanisms (46,47), but their distal intracellular effects seem to converge in the concerted stimulation of pregnenolone and progester- The present studies provide several significant and complementary lines of evidence that major actions of insulin are exerted at the level of the mitochondrial cytochrome P-450cscc, the terminal oxidase of the cholesterol side-chain cleavage system that catalyzes the rate-determining step in progestin biosynthesis (48). First, insulin enhances pregnenolone production from endogenous substrate, when further metabolism of pregnenolone is blocked.…”

“…However, the exact concentrations of insulin used in long-term (48 h) (47). Furthermore, in maturing follicles, steroidogenesis is closely regulated by estrogen and gonadotropic hormones (46,47), the latter presumptively acting through the cAMP effector system (46). Our in vitro studies indicate that insulin effectively amplifies the stimulatory actions of estradiol and cyclic AMP.…”