In-vivo induction of lactation in mammary glands isografted from neonates to pregnant mice.

Neonatal mammary rudiments isografted into C3H mice at mid-pregnancy responded to endogeneous gestational and puerperal hormonal stimuli in the hosts with morphogenetic and functional differentiation, and lactated within 9 days after birth. Neither lobulo-alveolar development nor lactation took place in neonatal mammary isografts when intra-uterine fetal death or stillbirth occurred in the pregnant host mice or when neonatal mammary rudiments were isografted into puerperal mice without being exposed to gestational hormonal stimuli before transplantation. Neonatal mammary rudiments isografted on day 0 post partum had much more extensive proliferation of end-buds when recovered on day 12 than on day 21 post partum. Histological features of neonatal mammary grafts closely reflected the endogeneous hormonal condition of the host mice.