Stimulation of hexose transport in cultured human skin fibroblasts by insulin

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Abstract
The effect of insulin on hexose transport in cultured human skin fibroblasts.Studies were carried out on cultures of human skin fibroblasts to explore the effect of insulin on hexose transport in serum‐starved monolayers. Insulin (100 mU/ml) stimulated 2‐deoxy‐D‐glucose transport (30% above control values) after 30 minutes exposure time, the response being similar up to four hours exposure to insulin. In several experiments (n = 22) employing three cell strains, insulin (100 mU/ml) exposure led to variable stimulation of 2‐deoxy‐D‐glucose transport (an average of 37% above control values, with a range of 0 = 120%). The insulin‐induced stimulation of 2‐deoxy‐D‐glucose transport showed a dose dependency with increasing amounts of insulin, the response being maximal at an insulin concentration of 100 mU/ml. Kinetic analysis of 2‐deoxy‐D‐glucose transport showed that insulin addition resulted in a slight change in the transport Km (3.13 to 4.06 mM) and a 1.8‐fold increase in the transport Vmax (17.6 nanomoles/mg protein/min to 32.1 nanomoles/mg protein/min). Insulin also stimulated the transport of 3‐0‐methyl‐D‐glucose while the hexokinase activity of the cells was not affected. Further, this insulin‐induced stimulation of sugar transport was not blocked by cycloheximide. The results indicate that insulin stimulated the stereospecific carrier‐mediated of hexose transport in cultured human skin fibroblasts.