THE INFLUENCE OF QUINONES ON THE OVARIAN RESPONSE OF IMMATURE RATS TO GONADOTROPIC STIMULATION1

Abstract

A series of quinones and napthoquinones have been tested in immature female rats for their ability to inhibit gonadotropins. Hydro-quinone, 2,6-dimethylhydroquinone and 2-methyl-napthoquinone produced no significant inhibition of the action of pregnant mare serum gonadotropin (PMS). Trimethylquinone and lapachol were effective in modifying the response of the ovary to PMS. The inhibition of a given dosage of PMS was proportional to the concentration of lapachol administered. Lapachol clearly depresses the ability of the ovary to respond at all levels of PMS, and exerts a marked inhibitory action even when the animal is given excessively large doses of the gonadotropin. The percentage inhibition produced by a given dosage of lapachol appears to be constant over the range of PMS concentrations that were tested (5-100 I.U.). In contrast, lapachol was unable to inhibit the action of chorionic gonadotropin (PU) or crude extracts of rat pituitaries. Neither hydrolapachol nor lomatiol was an effective inhibitor of PMS. There was a reduction in the succinoxidase activity of ovarian homo-genates from both PU and PMS treated rats injected with lapachol. The manner in which quinones inhibit the ovarian response to PMS is discussed.