Prolactin-independent induction of alpha-lactalbumin gene expression in mammary gland explants from pregnant Balb/c mice.

A four-fold increment of alpha-lactalbumin mRNA was induced in mammary gland explants from mid-pregnant Balb/c mice cultured for 24h in media containing insulin, cortisol and T3, and this response was enhanced by 40% with the addition of prolactin. In contrast, elevated beta-casein gene expression was evident only in explants cultured in media with insulin, cortisol, T3 and prolactin. These results suggest that the induction of the alpha-lactalbumin gene was prolactin-independent and did not result from retention of endogenous prolactin, or its effects, by the mammary explants.