11 beta-hydroxysteroid dehydrogenase activity in the mammary gland.

Levels of 11 beta-hydroxysteroid dehydrogenase activity in mammary gland homogenates from pregnant and lactating Sprague-Dawley rats were determined by incubation with [3H]corticosterone under standard conditions, followed by thin-layer chromatography of incubated media. Enzyme activity was high in virgin and pregnant rats, but fell soon after parturition, suggesting a possible role for this enzyme in the co-ordinate regulation of glucocorticoid effects on milk protein synthesis.