Effect of LH on Ovarian Ascorbic Acid Over a 24-Hour Period1

Publisher Website
Google Scholar
Abstract
The possibility of a 24-hr periodicity in ovarian responsivity to LH was investigated by measuring the ovarian ascorbic acid (OAA)-depleting effects of saline, 0.4 μg LH and 1.6 μg LH, administered at 4-hr intervals over a 24-hr period, in immature gonadotropin-primed rats in 2 separate experiments. A drop in OAA levels in the saline-injected rats occurred between 2 and 6 PM in both experiments, suggesting either an endogenous release of LH or a spontaneous timerelated fall in OAA concentration independent of hypophysial secretion. OAA levels (uncorrected for saline values) in the LH-treated rats also varied significantly with time. When these levels were corrected for simultaneous values in the saline-treated rats, OAA (0.4 μg LH)/OAA (saline) was inversely related to the saline-induced OAA levels; however, OAA (1.6 μg LH)/OAA (saline) was independent of the “saline” levels. These corrected OAA responses to LH still showed some alterations with time of day. However, while the time-ofday effect for the saline treatment was temporally consistent over the 24-hr period in both experiments, it was not so for the 2 LH treatments–peaks and troughs in the OAAdepleting activity of the administered LH occurred at different times over the 24-hr period in the 2 experiments. (Endocrinology76: 276, 1965)