The interaction of cortisol and prostaglandins on the phenotypic expression of the alpha-lactalbumin gene in the mouse mammary gland in culture.

Addition of cortisol at concentrations above 300 nM selectively inhibited the synthesis of alpha-lactalbumin and the accumulation of its mRNA in the mouse mammary gland cultured in the presence of insulin and prolactin, whereas the same treatment augmented casein synthesis and the accumulation of casein mRNA. Prostaglandin E2 or F2 alpha reversed the inhibitory effects of cortisol in a dose-dependent manner, without affecting casein production. The levels of prostaglandin E2 or F2 alpha in tissue explants cultured with insulin and prolactin increased about 2.6-fold over those in uncultured tissue, and the addition of cortisol decreased these levels approximately 2-fold. These results indicate the ability of prostaglandins to counteract the inhibitory effect of cortisol on the alpha-lactalbumin gene expression in the mouse mammary gland.