The effect of luteinizing hormonereleasing hormone (LH-RH) on pituitary cytology was investigated in intact, hemicastrated, and castrated male and female rats using electron and light microscopy. Two hundred ng of LH-RH were injected into the carotid artery, and the animals were sacrificed 1, 3, and 9 min after the injection. Study of LH-containing gonadotrophs by an immunocytochemical method using peroxidase- labeled antibody showed depletion of peroxidase reactivity of LH cells 1 min after injection of LH-RH in intact and hemicastrated proestrous rats, and after 9 min in the castrated females. Serum LH levels measured by radioimmunoassay were found to be significantly elevated 3 and 9 min after LH-RH injection in intact, hemicastrated and castrated male and female rats. Serum FSH levels had risen 1, 3, and 9 min after injection of LH-RH in the intact males and hemicastrated proestrous females, had fallen 1 and 3 min after injection in the hemicastrated male and had not changed 1, 3, or 9 min after injection in the castrated male and females.
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