Effect of vitamin A deprivation on maintenance of rat mammary tissue and on the potential of the epithelium for hormone-dependent milk protein synthesis.

Mammary tissue from rats severely deficient in vitamin A was compared with that from control animals. Glands from the deficient animals weighed only about 60% as much as those from control rats, a reflection largely of loss of material from the mammary fat pad. By contrast, vitamin A-deficient glands had as much epithelium as control glands. Furthermore, explants from the deficient glands were as responsive to insulin, glucocorticoid, and PRL as explants from control glands, in terms of the induction of casein synthesis and the alpha-lactalbumin and galactosyltransferase activities. It appears that vitamin A does not have a physiological role either in the maintenance of rat mammary epithelium or in its potential for hormone-dependent phenotypic expression. The results suggest that the anticarcinogenic activity of retinoids on rat mammary gland reported previously may lie outside the purview of these aspects of the mammary cell.