Luteinizing hormone depletes ascorbic acid in preovulatory follicles

Objective: The objective of the present studies was to determine whether luteinizing hormone (LH) depletes ascorbic acid in the preovulatory follicle. Design: Controlled, prospective experimental study. Setting: University-based research center. Animal(s): Sprague-Dawley female rats. Intervention(s): Follicular growth and ovulation were induced in immature rats by gonadotropin treatment. Main Outcome Measure(s): Analysis of ovary, follicle, and oocyte levels of ascorbic acid by colorimetric analysis and high-pressure liquid chromatography. Result(s) : Ovarian ascorbic acid was maximally depleted (50%) within 2 h of LH treatment and was sustained for 8 h. Follicle ascorbic acid levels were unchanged 1 h after LH injection but were significantly reduced within 2 h (40%). Incubation of isolated preovulatory follicles for 3 h with hCG or with menadione (a generator of oxygen radicals) reduced ascorbic acid levels. Isolation of cumulus-enclosed or denuded oocytes depleted ascorbic acid to undetectable levels, but follicular ascorbic acid levels were only moderately depleted by isolation and incubation. Accumulation of ascorbic acid by oocytes was significantly enhanced by the presence of intact cumulus cells. Conclusion(s): Elevation of LH and the production of oxygen radicals deplete ascorbic acid in the preovulatory follicle.