Fig. 3. Expression of apoptosis regulators in Lif^-;/-; and wild-type mammary gland. (A) Regulation of STAT proteins, milk protein and apoptosis related protein expression in involuting glands in absence of LIF. The levels of pSTAT5, total STAT5, pSTAT1, STAT1, ß-casein, Bcl-x, Bax, p53, p21 and ERK1/2 in mammary glands from 2 day involuting mice were determined by western blot analysis. Extract from interferon gamma-treated KIM-2 cells was used as positive control for pSTAT1 and STAT1. Graphs indicate densitometry analysis for three independent mice, mean±s.e.m.. Lif^-;/-;, black bars; Lif^+/-;, white bars. (B) Expression and activation profiles of STAT3 and ERK1/2 during mammary gland development. Western blot analysis of wild-type mammary glands harvested at indicated time points The blot was probed with antibodies specific for pSTAT3, total STAT3, pERK1/2 and total ERK1/2. d Preg, day pregnancy; d Lac, day lactation; h Involution, hours involution.