PANCREATIC-ISLET BLOOD-FLOW IN THE RAT AFTER ADMINISTRATION OF ISLET AMYLOID POLYPEPTIDE OR CALCITONIN-GENE-RELATED PEPTIDE

Anesthetized male Sprague-Dawley rats (350-400 g) were injected intrav enously with either 0.1, 1, 15, or 25 nmol rat islet amyloid polypepti de (IAPP), 65 or 650 pmol rat calcitonin gene-related peptide (CGRP), or saline alone. IAPP at the two highest doses decreased the mean arte rial blood pressure (BP), increased blood glucose concentrations, and decreased serum insulin concentrations. CGRP at both doses decreased t he BP but did not affect the blood glucose concentrations. The blood f low to the whole pancreas, pancreatic islets, adrenal glands, colon, d uodenum, liver, and kidney was measured with a microsphere technique 3 0 min after administration of IAPP and 3 min after injection of CGRP. The two higher doses of IAPP (15 and 25 nmol) markedly reduced the who le pancreatic blood flow, whereas the islet blood flow remained unaffe cted. This resulted in an increase in the fraction of whole pancreatic blood flow diverted through the islets from similar to 10 to 17%. No blood flow changes in the pancreas or the islets were observed when 0. 1 or 1 nmol IAPP was injected. CGRP at both doses caused a decrease in both whole pancreatic and islet blood flow. No changes in fractional islet blood flaw were observed, despite similar effects on mean arteri al BP as observed after IAPP injections. Neither adrenal, duodenal, co lonic, hepatic, skeletal muscle, nor renal blood flow were significant ly affected by any of the concentrations of IAPP used, whereas 650 pmo l CGRP decreased both duodenal and colonic blood flow. We conclude tha t IAPP and CGRP have different effects on pancreatic islet blood flow and that IAPP may be of importance for islet blood flow regulation.