Measurement of blood flow in pancreatic islets of the rat: effect of isoproterenol and norepinephrine.

Blood flow to the pancreatic islets of the anesthetized rat has been measured by application of microspheres, intravital staining of the endocrine tissue by Dithizon, and induction of organ transparency by incubation in glycerol. Thus the microspheres could be counted separately in the islet tissue and in the remaining organ. The total pancreatic blood flow in the rat amounted to 0.48 +/- 0.04 ml.min-1.g-1 and the flow fraction of the islet tissue to 1.22 +/- 0.09%, corresponding to a flow rate through the pancreatic islets of 5.42 +/- 0.63 microliters/min. When isoproterenol was applied (0.1 and 1.0 micrograms.kg-1.min-1 iv for 15 min), total pancreatic blood flow rose to 0.60 +/- 0.08 and 0.98 +/- 0.10 (P less than 0.01) ml.min-1.g-1, whereas the flow fraction to the islets decreased to 0.82 +/- 0.08 (P less than 0.01) and 0.61 +/- 0.07% (P less than 0.01). The absolute islet perfusion remained nearly unchanged. Norepinephrine (2.0 and 5.0 micrograms.kg-1.min-1 for 15 min) similarly increased total blood flow to 0.78 +/- 0.08 (P less than 0.01) and 0.64 +/- 0.08 ml.min-1.g-1) while reducing the islet flow fraction to 1.15 +/- 0.13 and 0.83 +/- 0.05% (P less than 0.01). The absolute flow rate through the islet tissue did not change significantly. The conclusion may be drawn from these experiments that changes in total pancreatic blood flow are not necessarily accompanied by corresponding changes in the perfusion rate of the endocrine islet tissue.