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Adrenal-Gonad Interactions in Cattle. Corpus Luteum Function in Intact and Adrenalectomized Heifers^{1 ,2,}

Iowa State University^,5, Ames 50011

⁴ To whom reprint requests should be sent. Current address: Dept. of Vet. Biosci., Univ. of Illinois, Urbana 61801.

Abstract

To determine the effect of the hyperadrenal state on corpus luteum (CL) function, we treated intact and adrenalectomized (ADRX) heifers with adrenocorticotropin (ACTH) and hydrocortisone. ACTH treatment of intact heifers by infusion of 1 mg 1–24 ACTH/24 hr from day 2 to 25 of an estrous cycle increased progesterone concentrations in plasma to 4 ± .52 ng/ml plasma on days 3 to 4. Thereafter, progesterone concentrations declined, indicating severe suppression of CL function as compared to that of control heifers. Similar infusions of ACTH to ADRX heifers did not alter CL function as reflected by progesterone concentrations in jugular plasma. Infusion of ADRX animals with hydrocortisone succinate (100 mg/24 hr) decreased progesterone in plasma during the cycle, with maximum values averaging <4 ng/ml, compared to concentrations of 6 to 7 ng/ml in control ADRX heifers. Chronic administration of ACTH or hydrocortisone to heifers caused a decreased progesterone secretion during the luteal phase of the estrous cycle. On the basis of these results, we suggest that stress, as indicated by the hyperadrenal state, could inhibit progesterone secretion by the corpus luteum.

¹ Submitted to Iowa State Univ. by G. O. da Rosa in partial fulfillment of the requirements for the Ph.D. degree.

² The authors gratefully acknowledge the assistance of R. Strohbehn, S. Li and R. Van Zee in the sample collection and assay procedures. We also express our thanks to Dr. J.J. Chart of the Ciba-Geigy Company for contributing the Synacthen and to Dr. J. Lauderdale of the Upjohn Company for providing the hydrocortisone succinate. This work was supported in part by USPHS, NICHD Grant No. R01-HD 08698.

³ Current address: Universidade Estadual de Mato Grosso, Campo Grande, Mato Grosso do Sul, Brazil.

⁵ Veterinary Medical Research Institute, College of Veterinary Medicine.