Lactose synthesis and the utilisation of glucose by rat mammary acini

Abstract

1. 1. Glucose uptake and lactose synthesis were measured in acini prepared from lactating-rat mammary gland and suspended in medium 199. 2. 2. Changes in the rate of glucose uptake, due to different concentrations of medium glucose or to the inclusion of phloretin or theophylline. were accompanied by larger changes in the rate of lactose synthesis. 3. 3. No clear evidence for cyclic nucleotide control of lactose synthesis was obtained. 4. 4. Direct measurement of intracellular glucose concentration (0.45 ± 0.08 mM) showed that it must be a rate-limiting factor for lactose synthesis and that glucose transport from the plasma into the mammary cell must be rate-limiting for glucose metabolism in general.