Effects of insulin, cortisol and prolactin on lipid, protein and casein syntheses in goat mammary tissue in organ culture.

The actions of insulin, prolactin and cortisol on protein, lipid and casein syntheses were examined in goat mammary explants in culture. The synthesis of the three products was stimulated by insulin and prolactin associated or not with cortisol. Casein synthesis was stimulated only when prolactin was present in the culture medium. Prolactin alone was able to significantly support the induction of casein synthesis. After preculture in the presence of insulin alone, the tissue lost part of its capacity to respond to the prolactin stimulus but, when precultured in the presence of insulin + cortisol, it retained its total sensitivity. These data suggest that insulin, prolactin and cortisol are involved in the maintenance of goat mammary tissue in culture but that prolactin essentially stimulates milk synthesis.