Rat mammary gland metabolism relative to epithelial and connective tissue content

Abstract

The respiration rate of rat mammary gland slices increased directly with the epithelial proliferation induced by pregnancy and lactation. In the absence of glucose the respiration was depressed, particularly in slices with the largest epithelial content. Dinitrophenol (5 x 10–5 m) provided a metabolic distinction between the epithelium of pregnant and lactating mammary glands; it stimulated the respiration of the former and depressed the respiration of the latter. The rate of anaerobic glycolysis (q1acN2) for mammary epithelium was adduced to be 4–5 µl/hr mg dry nonfat tissue and the rate remained in that range during lactation and pregnancy; the rate of aerobic glycolysis increased during pregnancy and decreased during lactation. Alkaline phosphatase activity did not vary directly with the mammary epithelium content and it was suggested that the rate of epithelial cell proliferation (mitoses) and hormonal factors might also be of importance in determining the total activity observed. The increase in glucose 6-phosphate dehydrogenase and 6-phosphogluconic acid dehydrogenase activity during pregnancy and at the onset of lactation was not directly related to the increase in mammary epithelium.