Strain Differences in Response of the Mouse Mammary Gland to Hormones In Vitro

Summary

Seven strains of mice were examined in regard to the hormonal requirements for the induction of mammary lobuloalveolar differentiation in vitro. The RIII and I^s required 5 days of pretreatment in vivo with estradiol and progesterone to show development in vitro; DBA/2, C3H, and BALB/c required 9 days; C57BL and A required 15 days. A greater length of pretreatment was correlated with the absence of the “inherited hormonal influence.” The minimal hormonal requirements in vitro varied with different strains. A concentration of 0.1 μg aldosterone per ml of medium was adequate for all strains except the A, which needed 1.0 μg/ml. Insulin requirements ranged from 0.5–2.5 μg/ml; prolactin and growth hormone requirements, from 0.1–5.0 μg/ml. These in vitro requirements and the “inherited hormonal influence” were not correlated.