Secretin and pancreatic islet blood flow in anesthetized rats: Increased insulin secretion with no augmentation of blood perfusion

Secretin is a stimulator of both endocrine and exocrine secretions of the p ancreas, and we aimed to evaluate its effects on splanchnic blood flow in r ats with a microsphere technique. Anesthetized rats were infused with secre tin (0.5 or 2.0 mug/kg body weight/hr) for 10 minutes. Some animals were no rmoglycemic, whereas other received a glucose injection 3 minutes before bl ood flow measurements. Secretin did not affect serum insulin concentrations in normoglycemic animals but consistently led to higher insulin concentrat ions in the hyperglycemic rats. Total pancreatic blood flow was increased b y the highest secretin dose in normoglycemic animals, whereas no effects we re seen in the hyperglycemic rats. Administration of glucose caused a prono unced increase in islet and fractional islet blood flow in saline-infused a nimals. Secretin affected neither islet nor fractional blood flow in normog lycemic or hyperglycemic rats. Glucose administration increased duodenal bl ood flow in animals infused with saline and both duodenal and colonic blood flow in rats given the lowest dose of secretin. No effects on either colon ic or duodenal blood perfusion were seen in animals infused with the highes t dose of secretin. Secretin mainly affects blood flow to the whole pancrea s and not that of the islets. Furthermore, glucose-induced insulin release can be achieved without a simultaneous increase in islet blood flow; that i s these two events may be dissociated from one another.