title: Sodium-dependent regulation of steroidogenesis in rat granulosa cells: possible involvement of a Na+/H+ antiport.
abstract: The possible role of Na+/H+ antiport in the gonadotropic regulation of steroidogenesis was examined in rat granulosa cells incubated for up to 6 h in a chemically defined medium in the absence or presence of Na+ (128 mM), gonadotropin (FSH or LH; 0-500 ng/ml), dibutyryl cyclic AMP [Bu)2cAMP; 2 mM) and amiloride (0-1 mM). Replacement of Na+ (Na+0) in the incubation medium with choline chloride resulted in a marked decrease in basal and LH-, FSH- and (Bu)2cAMP-stimulated progesterone and 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OH-P) synthesis in vitro. The Na+/H+ exchange inhibitor, amiloride significantly suppressed basal and hormone-stimulated progestin production dose-dependently in the presence of Na+0. However, it was without effect in Na+-deficient medium. The effect of the inhibitor on progestin production appeared to be directed at specific step(s) involved in the synthesis of pregnenolone, as concentrations of amiloride which inhibited progesterone production failed to influence the metabolism of exogenous pregnenolone to progestins. Cell viability and the incorporation of [3H]leucine into acid-precipitable material were not affected by amiloride. Our findings support the contention that extracellular sodium is important for steroidogenesis in rat granulosa cells. The inhibition by amilordie indicates an involvement of the Na+/H+ exchange in the regulation of this granulosa cell function.
authors.affiliation: Department of Obstetrics and Gynecology, University of Ottawa, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.forename: E K
authors.initials: EK
authors.lastname: Asem
authors.forename: B K
authors.initials: BK
authors.lastname: Tsang
mesh_terms: D004092:20-alpha-Dihydroprogesterone / Q000096:biosynthesis*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000494:pharmacology; D011284:Pregnenolone / Q000096:biosynthesis; D011374:Progesterone / Q000031:analogs & derivatives* / Q000096:biosynthesis*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology*; D017923:Sodium-Hydrogen Exchangers
chemical_list: D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D004092:20-alpha-Dihydroprogesterone; D011374:Progesterone; D003994:Bucladesine; D011284:Pregnenolone; D000584:Amiloride; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D012964:Sodium