INDUCTION OF LACTOSE SYNTHESIS BY PROLACTIN IN RABBIT MAMMARY GLAND EXPLANTS

The rate of biosynthesis of lactose from [14C]glucose was used to study the action of different hormone combinations on cultures of mammary explants from pseudopregnant rabbits. Insulin with or without cortisol had no effect, but insulin with prolactin induced lactose synthesis in vitroeven when prolactin was not added to the culture medium until 48 h after culture began. Insulin together with cortisol and prolactin produced a greater response when used from the beginning of culture. Differences between these results and those obtained with mammary tissue from pregnant mice are discussed.