Structure and biochemistry of normal and mutant ( [formula omitted]) mouse mammary tissue during gestation and lactation

Abstract

Mammary gland structure and function in mutant hub hub (hyper-unconjugated bilirubinemia) mice were compared to controls (+/ hub). Pups from normal and mutant mice have decreased weight gain when suckled by mutant dams. Samples examined by light microscopy showed no apparent differences when excised at mid- (day 9–11) and late- (day 17–18) gestation, and early (day 3–4) lactation. There was some evidence that early involution may be occurring in the hub mice at midlactation (day 10–11). Total DNA was greater (33%) when sampled at midgestation in the normal mice but lower (20%) at late gestation when compared to the hub mice. Total protein concentration was higher (132%) during late gestation in hub mice but was lower (34%) by early lactation when compared to normal mice. Epidermal growth factor (EGF) in normal mice was 79% and 71% higher in early and midlactation, respectively, than in mutant mice. There were no differences in serum concentrations of progesterone between strains at any stage. From these results, there is a suggestion of premature production of proteins, possibly followed by early involution in hub mice. Milk yield was less in mutant mice than in normal mice. Low concentrations of EGF during lactation in mutant mice may partially account for the decreased growth observed in mutant and normal pups suckling mutant dams.