Oxytocin and the Secretion of Luteinizing Hormone in Cattle

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Abstract
Frequent collection of jugular blood samples on days 2 through 6 of the estrous cycle from three control and three treated heifers showed that plasma concentrations of LH were not affected by exogenous oxytocin for a period up to 8 hr. postinjection. A similar experiment employing blood samples collected 10 to 21 hr. after injection, from three control and three treated heifers, again showed that plasma LH levels were not lowered or elevated by oxytocin. Pituitary content and concentrations of LH and FSH in these animals, sacrificed at day 7 of the estrous cycle, had not been altered by oxytocin treatment. Corpus luteum progesterone concentration and total progesterone content were not significantly reduced by oxytocin treatment. Peripheral blood concentrations of LH were higher on Days 3 and 4 than on days 2, 5 and 6 of the bovine estrous cycle. These elevated LH values represent a normal, physiologic stimulus for maximal luteal development and increased corpus luteum function which occurs after day 4 of the cycle. Copyright © 1971. American Society of Animal Science . Copyright 1971 by American Society of Animal Science.