Abstract
The hypothesis that prostaglandin E2 (PGE2) is a circulating mediator of adrenocorticotropic hormone (ACTH) secretion in sheep was tested in conscious adult ewes using 30-min carotid artery infusions of 0, 5, 10, 100, and 500 ng.kg-1. min-1 PGE2 in saline. ACTH, cortisol, and aldosterone were significantly increased during the 500 ng.kg-1.min-1 infusion (166 +/- 61 to 233 +/- 38 pg/ml, 27 +/- 5 to 45 +/- 2 ng/ml, and 52 +/- 11 to 85 +/- 25 pg/ml, respectively). PGE2 infusions of 100 ng.kg-1.min-1 increased ACTH from 104 +/- 31 to 168 +/- 31 pg/ml and cortisol from 18 +/- 5 to 42 +/- 2 ng/ml. PGE2 infusions did not increase arginine vasopressin, plasma renin activity, or hematocrit. Heart rate and mean arterial pressure were minimally but significantly increased during the 500 ng.kg-1.min-1 infusion, from 84.9 +/- 2.8 to 99.3 +/- 5.4 beats/min and 95.5 +/- 1.8 to 101.0 +/- 3.4 mmHg, respectively. In a second study to test whether lower infusion rates of PGE2 increase plasma ACTH in sheep with lower resting hormone concentrations, sheep were infused and sampled through a tether system, preventing any disturbances due to human contact the day of an experiment. For all infusion rates ACTH baselines were less than or equal to 55 +/- 17 pg/ml, and cortisol baselines were less than or equal to 6 +/- 3 ng/ml.(ABSTRACT TRUNCATED AT 250 WORDS)
Published Version
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