IN-VITRO UPTAKE AND METABOLISM OF [3H]CORTICOSTERONE BY MAMMARY GLANDS FROM PREGNANT, LACTATING AND POST-LACTATIONAL RATS AND BY PARAMETRIAL ADIPOSE TISSUE FROM LACTATING RATS

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Abstract
The study was designed to determine the influence of the physiological state on the invitro uptake and metabolism of glucocorticoid hormone by the mammary gland. [3H]Corticosterone was accordingly incubated with minced mammary glands from pregnant, lactating and post-lactational rats. The total uptake of [3H]corticosteroid was obtained from the concentration of radioactivity by the tissue and the specific activity of the steroid substrate. The extent of 21-acylation was determined as the percentage of the radioactivity in the chromatographed tissue extracts attributable to 21-acyl-[3H]corticosterone. The results indicated that the uptake of [3H]corticosteroid increased with advancing pregnancy, attained a high plateau level during lactation, and steadily declined during the post-lactational period. The extent of 21-acylation of [3H]corticosterone varied from 10 to 40%, fluctuating widely in all physiological states, particularly during the post-lactational period. It was inferred that the stromal elements, presumably the adipocytes, of the mammary gland can also acylate the corticosteroid hormone, a view which gained experimental support from similar studies with minced parametrial adipose tissue from lactating rats.