Uptake and release of ascorbic acid by rat Leydig cells in vitro.
The mechanism by which ascorbic acid is transported into rat Leydig cells in vitro was investigated. Transport of [14C]ascorbic acid was temperature-dependent and inhibited in the absence of sodium in the incubation medium. The uptake of [14C]ascorbic acid was saturable (apparent Km approximately equal to 33 microM, Vmax approximately equal to 20 pmol/10(6) cells/min) and stereospecific. Uptake was not affected by removing glucose from the incubation medium, indicating that no significant uptake was occurring via the glucose transport system. Transport of [14C]ascorbic acid into Leydig cells was not affected by testosterone concentrations up to 7 microM or by LH at a concentration that causes maximum androgen secretion. Leydig cells preloaded with [14C]ascorbic acid rapidly released radioactivity into the incubation medium, a process that was unaffected by the presence of LH. The results suggest that ascorbic acid uptake by Leydig cells is by an electroneutral, sodium-dependent co-transport mechanism as in some, but not all, other types of cells.
Department of Physiology, Dalhousie University, Halifax, Nova Scotia.
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Moger
D000818:Animals; D001205:Ascorbic Acid / Q000493:pharmacokinetics*; D066298:In Vitro Techniques; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000494:pharmacology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000502:physiology; D013739:Testosterone / Q000096:biosynthesis
D013739:Testosterone; D007986:Luteinizing Hormone; D012964:Sodium; D001205:Ascorbic Acid