Effect of Intracarotid Infusion of Prostaglandin F2α on Plasma Prolactin and Growth Hormone in Bulls

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Abstract
Two experiments were designed to localize the action of systemically administered PGF2α in causing increased plasma prolactin and growth hormone in bulls. Five bulls approximately 18 months old were each given 3-hr infusions of PGF2α at 0 (saline), 20, 200, and 2,000 ng/min into a carotid artery, and 2,000 ng/min and .2 mg/min into a jugular vein. Administration of PGF2α at .2 mg/min into a jugular vein was calculated to represent a dose of about 2,000 ng/min reaching the head. The design was a Latin square with 12 hr between beginning 3-hr infusions. Jugular vein blood was sampled at least every 30 min throughout. The high jugular dose (.2 mg/min) caused significantly increased plasma prolactin and growth hormone concentrations compared to saline controls. The 2,000 ng/min dose given via the carotid artery also was effective in increasing plasma prolactin and growth hormone, whereas a dose of 2,000 ng/min given into the jugular vein and 20 and 200 ng/min into the carotid artery were ineffective. In the second experiment, a 50 µg bolus of PGF2α given into a carotid artery in four bulls caused release of prolactin within 4 min, but growth hormone was not affected significantly. It is concluded that the major site of systemic PGF2α in enhancing prolactin and growth hormone secretion is the pituitary or the brain, with no more than minor indirect action at the periphery. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.