Insulin stimulation of glycogen synthase in cultured human diploid fibroblasts.
The effect of insulin on glycogen synthase activity in human diploid fibroblasts has been studied. As little as 2 X 10(-10) M insulin increased the glycogen synthase / activity without changing the total activity. Stimulation occurred within 5 min and became maximal in 30 min. A half-maximal increase of / activity was achieved at 3 X 10(-9) M insulin. Glucose starvation increased the magnitude of response of glycogen synthase to insulin but did not change the insulin concentration necessary to give a half-maximal stimulation. Glucose increased the basal level of / activity in human diploid fibroblasts; the effect of insulin was additive. During in vitro senescence the total glycogen synthase activity declined, but the concentration of insulin that produced a half-maximal stimulation remained unchanged. These data indicate that regulation of glycogen synthase activity in human diploid fibroblasts is responsive to physiologic insulin levels and that the system provides a useful model for the in vitro study of insulin sensitivity.
D002478:Cells, Cultured; D004171:Diploidy; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology; D005947:Glucose / Q000494:pharmacology*; D006006:Glycogen Synthase / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D012867:Skin / Q000201:enzymology*
D007328:Insulin; D006006:Glycogen Synthase; D005947:Glucose