[Analysis of breast cell differentiation in tissue culture under the influence of hormones]

Effects of insulin, hydrocortisone and prolactin on cell differentiation were studied in mammary gland tissue culture of pregnant goats. The morphological evidence suggests that the administration of the above hormonal triad during cultivation contributes to the development of "growth zone" around the explantat on the filter and to morphological changes of tissue which become specific of the mammary gland tissue in normally lactating animals. The metabolism of nuclear proteins, DNA synthesis and cell proliferation at the initial stages of epithelium development are demonstrated to be regulated by insulin together with hydrocortisone. The synthesis of milk proteins is influenced by prolactin. The effect of prolactin is realized only in newly-formed postmitotic population of secretory cells.