title: Characterization of insulin binding sites in cultured smooth muscle cells of rat aorta.
abstract: Insulin receptors could be demonstrated in cultured smooth muscle cells of rat aorta. The specific binding of 125I-insulin was time-, temperature- and pH-dependent. The optimal temperature for our studies was 12 degrees C. At this temperature maximal specific binding was 0.5% of total counts at 120 min incubation. The pH-optimum for the binding process was between 7.5 and 8. Degradation of 125I-insulin at 12 degrees C was 14%, no degradation of binding sites could be measured at this temperature. Dissociation of 125I-insulin was rapid. 50% of the labeled hormone remained associated with the cells. Half-maximal inhibition of 125I-insulin binding was produced by insulin at 4 X 10(-11) mol/l. Scatchard-analysis gave curvilinear plots, that may suggest negative cooperativity. Specificity of binding was studied in competition experiments between 125I-insulin, insulin, proinsulin, insulin-like growth factors and human growth hormone. Half-maximal inhibition of 125I-insulin binding was produced by proinsulin at 2 X 10(-9) mol/l and by insulin-like growth factors at 9 X 10(-9) mol/l. Human growth hormone had no significant effect on the insulin binding.
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism; D001161:Arteriosclerosis / Q000378:metabolism; D002478:Cells, Cultured; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D051381:Rats; D011972:Receptor, Insulin / Q000032:analysis*
chemical_list: D011972:Receptor, Insulin