Effect of mirex on induced ovulation in immature rats (38550).

PMS-induced ovulation was significantly inhibited in 28-day-old immature rats by acute administration of the chlorinated pesticide Mirex. Numbers of ova recovered were reduced by 40-80% from controls with dose levels of Mirex ranging from 0.4 to 50 mg per animal. When injections of Mirex 48 hr after PMS were followed by HCG the inhibitory effect of the insecticide was overcome, suggesting that the ovary is not the primary site of action. Injections of Mirex at intervals preceding the PMS-induced LH surge resulted in an inhibition of ovulation. Administration of the insecticide after the expected release of LH was ineffective. There was no indication of a premature or delayed release of LH due to injection of Mirex. TPHE DATA SUGGEST THAT Mirex inhibits PMS-induced ovulation by an unknown effect upon neural mechanisms controlling the release of LH.