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Title: Pancreatic hormone receptors on islet cells. Author: Van Schravendijk CF, Foriers A, Hooghe-Peters EL, Rogiers V, De Meyts P, Sodoyez JC, Pipeleers DG. Journal: Endocrinology; 1985 Sep; 117(3):841-8. PubMed ID: 2990873. Abstract: To assess whether islet cells are equipped with recognition units which allow an intra-islet regulation via released hormones, the presence of insulin and glucagon receptors is investigated on purified pancreatic A and B cells. Mono-[125I]glucagon is shown to bind specifically to islet B cells, with similar binding characteristics as in isolated hepatocytes but involving less receptors per cell (2.10(4) per B cell vs. 8.10(5) per liver cell). Binding is half-maximally displaced by 5.10(-9) M glucagon, a concentration known to induce half-maximal biological effects in isolated B cells. These results are compatible with a regulatory role of glucagon in the insulin release process. No specific binding of [125I]tyr-A14-insulin is detected on pancreatic A cells. In order to increase receptor assay sensitivity, [123I]tyr-A14-insulin is prepared with at least 5-fold higher specific activity. Its validity for in vitro receptor analysis is demonstrated in IM-9 lymphocytes, where insulin binding is detectable down to 10(4) cells/ml. However, no insulin-binding sites are identified on pancreatic A cells, even at 10(6) cells/ml. If isolated A cells contain high affinity insulin receptors, their number should be inferior to 400 per cell, which is 50- to 500-fold lower than in classical insulin target cells. These findings explain the insensitivity of the glucagon release process to acute exposure to insulin.[Abstract] [Full Text] [Related] [New Search]