High performance liquid chromatographic analysis of polypeptide hormones in transplanted rat islets

This report describes high performance liquid chromatographic analysis of transplanted pancreatic islets. A reversed phase ODS column made it possible to measure rat insulin I, II, rat C-peptide I, II and glucagon simultaneously in isolated rat islets without using radioisotopes. Freshly isolated islets contained 118.0 +/- 9.7 ng (mean +/- SE, n = 6) insulin and 3.01 +/- 0.60 ng glucagon per islet. The insulin I/II ratio was 1.22 +/- 0.03. Isolated islets were then cultured in vitro or transplanted into mice under the renal capsule. Transplantation induced mild hypoglycemia in the recipients. The graft mean survival time was 7.2 +/- 0.4 days (n = 5). Both cultured (n = 7) and transplanted (n = 6) islets showed similar alterations of polypeptide hormones on day 4. Insulin decreased to one third and glucagon remained unchanged. The insulin I/II ratio increased twofold. In conclusion, it was suggested that the general fate of isolated islets was caused by ischemia and denervation. Relatively, ischemia may not damage alpha cells but may damage beta cells because alpha cells are peripherally located. Denervation may release beta cells from a resting state under neural tonic inhibition. Mild hypoglycemia and an increased insulin I/II ratio were related to the accelerated insulin synthesis in the isolated islets.