PROLACTIN STIMULATES PROLIFERATION OF CULTURED HUMAN KERATINOCYTES

The effect of the pituitary hormone prolactin on in vitro proliferatio n of human keratinocytes has been studied. Cell proliferation was dete rmined by [H-3] thymidine incorporation and cell enumeration in cultur e. Physiologic concentrations of prolactin markedly stimulated prolife ration of newborn foreskin keratinocytes in serum-free medium. in addi tion, it was able to replace almost completely the growth-promoting ef fects of bovine pituitary extract, a commonly added supplement for ker atinocyte culture. This activity was also evident in the absence of ep idermal growth factor, but required the presence of insulin. Radioliga nd-binding studies confirmed the expression of specific prolactin bind ing sites (Kd 8.9 nM; 1350 sites per cell) on freshly procured keratin ocyte membranes. These results extend its hormonal influences to inclu de regulation of in vitro proliferation of human keratinocytes, and su ggest the possibility of a completely defined growth medium for kerati nocytes.