Mammary epithelial cells undergo structural and functional differentiation at late pregnancy and parturition to produce and secrete milk. Both TGF-β and prolactin pathways are crucial regulators of this process. However, how the activities of these two antagonistic pathways are orchestrated to initiate lactation has not been well defined. Here, we show that SnoN, a negative regulator of TGF-β s...

Closure of the tight junctions of the mammary epithelium has been shown to accompany the onset of copious milk secretion or lactogenesis, stage 2, in both goats and humans. Here we use injection of [(14)C]sucrose and FITC-albumin (fluorescein isothiocyanate-albumin) into the mammary duct to follow the course of tight junction closure during lactogenesis in mice. To examine the hormonal changes ...

OBJECTIVE The onset of copious milk secretion after birth is known as lactogenesis II. The objective of this study was to investigate the effect of preterm birth and antenatal corticosteroids on the timing of lactogenesis II after birth. METHODS Women who had received antenatal betamethasone treatment and were expressing for a preterm infant whose gestational age was <34 weeks (N = 50) were i...

The physiology of human lactation is described with secretions on mammary gland anatomy and development, the mechanisms of milk secretion and ejection, and the temporal sequence of events during the transition from pregnancy to lactation (lactogenesis). Finally, interactions between lactation and maternal metabolism are briefly described and the interaction of lactation with fertility discussed.

Activity of glucocorticoid receptor in mouse mammary cytosol changes during lactogenesis. The highest receptor activity is observed in the second half of pregnancy. The receptor from mammary glands from lactating and pregnant mice exhibits the same sedimentation pattern, as well as the same specificity and affinity for binding of steroid hormones.