Insulin and growth factors stimulate rapid posttranslational changes in glucose transport in ovarian granulosa cells

Abstract

The glucose analogues, 3-0-methyl-D-glucose and 2-deoxy-D-glucose, have been used to characterize glucose transport and its regulation by serum and growth factors in monolayer cultures of granulosa cells obtained from bovine ovaries. Uptake of 3-0-methylglucose was shown to be independent of the Na⁺-gradient, independent of energy, did not show accelerated exchange, and was stereospecific. Serum withdrawal resulted in a biphasic decrease in initial rates of glucose uptake with half-times for the two phases of 50 minutes and 3 hours. Insulin could prevent the decrease in uptake rates with a half-maximum concentration of 10.5 1/8 3 nM. Insulin was shown to stimulate DNA synthesis with a concentration of half-maximum response of 28 nM. Insulin or serum stimulation of 3-0-methylglucose uptake in serum-starved cells resulted in a two to threefold increase in initial rates, with a time for halfmaximum stimulation of 3 minutes. The insulin-stimulated increase was insensitive to cycloheximide and cyanide during the first 30 minutes, and this early, rapid stimulation was also produced by brain FGF (fibroblast growth factor), pituitary FGF, epidermal growth factor, calf serum, and some but not all samples of follicular fluid. Insulin also stimulated 2-deoxyglucose and a-aminoisobutyric acid uptake during the first 5 minutes of addition, and these early stimulations were shown to be posttranslational changes.