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Adrenocorticotropin Alteration of Bovine Peripheral Plasma Concentrations of Cortisol, Corticosterone, and Progesterone^{1, 2,}

Department of Dairy Science, University of Florida, Gainesville 32610

ABSTRACT

Seven Holstein cows, 60 to 90 days postpartum, received either 200 IU ACTH (n=4) or saline (n=3) intravenously with treatments reversed 2 days later. Blood samples (30 ml) were collected from indwelling jugular catheters at –60, 0 pre-injection, and 5, 15, 30, 45, 60, 120, 180, and 240 min postinjection. Solvent extraction, purification by Sephadex LH-20 column chomatography and competitive protein-binding analyses were used to isolate and quantify plasma cortisol, corticosterone, and progesterone. Mean cortisol (ng/ml) at the respective sampling times was 3.1 vs. 3.6 (saline vs. ACTH), 4.9 vs. 4.1, 5.9 vs. 33.7, 8.8 vs. 30.0, 4.8 vs. 45.8, 3.3 vs. 28.8, 3.2 vs. 31.3, 4.4 vs. 36.6, 2.6 vs. 26.8 and 5.2 vs. 34.7. Both the magnitude of the cortisol response and the interval to maximum response to ACTH varied among cows (P<.01). Adrenocorticotropin elicited a corticosterone increase (P<.01) concurrently with the cortisol increase, but it was of lower magnitude, reaching 7.6 ng/ml at 30 min. Mean progesterone at the respective times was 1.7 vs. 2.1, 2.4 vs. 2.0, 2.0 vs. 3.1, 2.0 vs. 4.5, 2.2 vs. 4.2, 2.5 vs. 4.2, 2.2 vs. 3.9, 2.3 vs. 2.4, 2.6 vs. 2.8 and 2.2 vs. 2.0 ng/ml, and the increase due to ACTH administration was significant (P<.025) between 15 to 60 min post-injection. Results suggest that the adrenal contributes a significant proportion of plasma progesterone.

¹ Florida Agricultural Experiment Station Journal Series 4321.

² Supported in part by a Biomedical Science Grant, National Institute of Health, Bethesda, Maryland 20014.

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