Effects of Insulin on Isolated Rat Mammary Cell Metabolism: Glucose Utilization and Metabolite Patterns1

Abstract

Insulin stimulated productions of C0₂, lactose and lipid from glucose by isolated mammary cells incubated in vitro 2- to 3-fold. Casein synthesis was only slightly stimulated by insulin. Increasing glucose concentrations in the medium did not reduce insulin stimulation of CO₂ and fatty acid productions but abolished insulin stimulation of glyceride glycerol synthesis. The contribution of the pentose phosphate pathway to glucose oxidation was enhanced by insulin as indicated by four separate methods of calculation. The data indicated that the triose phosphate isomerase reaction is in equilibrium in isolated mammary cells. Metabolite patterns in isolated mammary cells are similar to those observed in vivo when insulin is present. Calculated values of free nicotinamide adenine dinucleotides in isolated cells shifted toward a more reduced state when insulin was not added to incubation media. Changes in glucose-6-PO₄ levels are discussed in relation to hexokinase activity. (Endocrinology89: 1263, 1971)