ENZYMES OF LACTOSE BIOSYNTHESIS IN NORMAL AND HORMONALLY STIMULATED RABBIT MAMMARY GLANDS

The activities of uridine diphosphate glucose (UDPG) pyrophosphorylase and UDPG-4′-epimerase in mammary glands of rabbits were determined in late pregnancy and lactation. The activities in animals during the last 4 days of pregnancy and during days 0–4, 5–9 and 11–21 of lactation increased but the difference in the activities was significant between the days 5–9 and 11–21 only and for the pyrophosphorylase activity between days for 0–4 and 5–9.Prolactin and cortisol acetate given daily for 3 or 5 days to rabbits pseudopregnant for 15 days caused increases in enzyme activities that were several times greater than those found in controls. The enzyme activities in the stimulated glands were similar to those observed in early lactation.The levels of deoxyribonucleic acid/g. wet tissue were the same in the stimulated and lactating glands.