Comparative effects of secretin (SEC) and cholecystokinin-octapeptide (CCK-8) on pancreatic microcirculation

Using epifluorescent microscopy, we investigated the dynamic changes in pancreatic microcirculation in vivo after bolus administration of secretin (SEC) (0.1-10.0 micrograms/100 g body wt) and cholecystokinin-octapeptide (CCK-8) (0.005-1.2 micrograms/100 g body wt) in pentobarbital-anesthetized rats. Pancreatic capillary red cell velocity as a monitor for pancreatic capillary blood flow was measured in 1-min intervals from 2 min prior to 8 min following bolus infusion of SEC or CCK-8. Physiological concentrations of SEC did not increase pancreatic capillary blood flow. However, pharmacological SEC concentrations induced a dose-dependent increase in pancreatic capillary blood flow (to 162 +/- 19% of baseline; P < 0.05), due to an increase in blood flow velocity (to 153 +/- 18% of baseline; P < 0.05). In contrast, bolus administration of physiological CCK-8 concentrations, which have been proven to stimulate enzyme secretion, induced a transient and dose-dependent increase in pancreatic capillary blood flow (to 235 +/- 24% of baseline; P < 0.05), due to an increase in blood flow velocity (to 184 +/- 13% of baseline; P < 0.05) and capillary diameters (+0.63 +/- 0.15 micron; P < 0.05).