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Effect of Ovariectomy on Pituitary Gonadotropins in the Cow¹

Laboratory of Genetics and Department of Gynecology and Obstetrics, The University of Wisconsin, Madison 53706

ABSTRACT

To study changes in pituitary follicle-stimulating and luteinizing hormone contents following ovariectomy, 24 heifers were spayed on the day of estrus and sacrified on Day 17 or Day 42. Twelve intact heifers were sacrified on Day 17 of the estrous cycle. Individual anterior pituitary glands from all animals were assayed for follicle-stimulating hormone by biological assay, and for luteinizing hormone by radioimmunoassay. Pituitary glands from ovariectomized heifers did not differ significantly in fresh or dry weight from those of control animals. Follicle-stimulating hormone content in pituitary glands from all spayed heifers was higher (P < .001) than in intact heifers, whereas pituitaries from spayed heifers at Day 42 had more (P < .05) follicle-stimulating hormone than did those at Day 17. Luteinizing hormone content for the pituitary glands of the intact heifers was significantly (P < .005) higher than the average for glands from all spayed heifers.

¹ This work was done under a cooperative agreement between the Research Division of the College of Agricultural and Life Sciences, University of Wisconsin, and the Dairy Cattle Research Branch, USDA, Beltsville, Maryland. It was supported in part also by The Ford Foundation Grant 63-505 and by the Program Project in Genetics, Grant GM 15422, from the National Institutes of Health. Published with the approval of the Director of the Research Division of the College; Paper 1423 from the Laboratory of Genetics.