Insulin and glucagon binding and degradation by kidney cell membranes.
The binding and degradation of insulin and glucagon to kidney cell membranes was examined. Time- and temperature-dependent specific binding of [125I]iodo-insulin to kidney cell membranes was demonstrated. The membranes also degraded insulin in a time-, temperature-, and protein concentration-dependent manner. The apparent Km of the degradation was 2.7 x 10(-7) M. Glucagon degradation by the kidney membranes was extremely active. Per milligram of protein the kidney membrane was over 20 times as active as the liver membrane. Even at 4 C, significant glucagon degradation occurred. Because of this very active degradation, glucagon binding could not be accurately assessed. The kidney glucagon-degrading activity was inhibited by glutahione and EDTA but unaffected by N-ethylmaleimide, ACTH, or insulin, all potent inhibitors of liver glucagon degradation. The apparent Km for glucagon degradation by the kidney, however, was essentially identical with that for the liver, 2.4 x 10(-6) M.
D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D005934:Glucagon / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D008297:Male; D051381:Rats; D013696:Temperature
D007328:Insulin; D005934:Glucagon; D004492:Edetic Acid; D005033:Ethylmaleimide