Influence of insulin on maintenance and secretory stimulation of mouse mammary tissues by hormones in organ-culture.

Mouse mammary tissues from late prelactating, early prelactating, and nonpregnant multiparous female C3H/Crgl mice were subjected to various hormones in organ-culture in a synthetic medium. The three types of tissue were maintained with the addition of insulin and cortisol, to some extent with insulin alone, and not at all with cortisol alone. The more differentiated the tissue in the direction of secretory activity, the greater was the need for cortisol in addition to insulin for maintenance in vitro. Following culture in insulin and cortisol, mammary tissues showed one of the following responses: (1) alveolar maintenance with loss of secretory activity, (2) maintenance of the initial histologic structure, or (3) reorganization of alveolar epithelium. Addition of mammotropin and somatotropin to media containing insulin and cortisol maintained the secretory state of late prelactating tissue and stimulated early prelactating and nonpregnant tissues to secretory activity. The optimum concentrations of MH an...