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Journal of Dairy Science Vol. 61 No. 12 1709-1714
© 1978 by American Dairy Science Association ®
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Regulation of Cortisol Uptake in Mammary Tissue of Cows1

R. J. Collier2 and H. Allen Tucker

Animal Reproduction Laboratory, Department of Dairy Science, Michigan State University, East Lansing 48824

ABSTRACT

Mammary tissue explants from four nonlactating, nonpregnant cows were placed into culture with media containing various combinations of insulin, prolactin, growth hormone, 17ß-estradiol, dexamethasone, and progesterone. Combinations of insulin, prolactin, growth hormone, or 17ß-estradiol had no effect on cytoplasmic or nuclear uptake of tritiated Cortisol compared with values at zero time. Combinations containing dexamethasone or progesterone reduced cytoplasmic and nuclear uptake of tritiated Cortisol. To examine inhibition by progesterone of binding of tritiated Cortisol, mammary tissue from each of four lactating, nonpregnant and four nonlactating, nonpregnant cows were placed in flasks containing tissue culture medium 199, tritiated Cortisol (2 ng/ml), and progesterone at concentrations of 0, 10–12, 10–11, 10–10, 10–9, 10–8, 10–7, 10–6, or 10–5 x 6.4 M. Cytoplasmic uptake of tritiated cortisol into nonlactating tissue decreased linearly as progesterone increased, whereas tritiated Cortisol uptake in lactating tissue did not decrease until progesterone exceeded 10–7 M. We postulated progesterone is sequestered in milk fat of cytoplasm of lactating tissue whereas in nonlactating tissue progesterone is available to compete with Cortisol at sites of Cortisol binding.

FOOTNOTES

1 Michigan Agricultural Experiment Station Journal Article No. 8410. This research was supported in part by USPHS Grant HD-05750 and FD 00706.

2 Dairy Science Department, University of Florida, Gainesville 32611.






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Copyright © 1978 by the American Dairy Science Association ®.