摘要：Three kinds of plasma membranes in rat islet homogenate were fractionated on sucrose gradient centrifuged at 70000g (F1 : d20=1.14-1.18, F2 : d20=1.06-1.12, F3 : d20=1.02-1.05). Every fraction indicated both enzyme activities of 5'-nucleotidase and ATPase which were typical marker enzymes in pancreatic plasma membrane, and the D-[5-3H] glucose binding with them were dose-dependently inhibited by D-glucose, but not by L-glucose, D-galactose and 3-O-methyl-D-glucose. The D-[5-3H] glucose binding with only F2 fraction was inhibited by D-mannose and D-fructose which could stimulate insulin release (60%), phlorizin inhibited remarkably the binding with F3 fraction (68%), however, the D-[5-3H] glucose binding with either F1 or F2 fraction was slightly inhibited by preincubation with alloxan (0.2 mg/ml, 37°, 10min) (F1 : 29%, F2 : 39%) and that with F3 fraction was not effective (4%). It was found that the insulin release from the B granules which distributed in the pellet fraction on sucrose gradient centrifuged at 70000g, was induced by the interaction with F2 fraction. Each maximal capacity of glucose binding site in F1, F2 and F3 fractions was estimated at 3.2, 1.0 and 3.2 μmol/mg membrane protein, respectively, from those Scatchard's plots for the glucose binding. Consequently, it was estimated that the membrane which associated with insulin release was contained in F2 fraction among three fractions from the islet homogenate.
