Feline cholescintigraphy. Studies on role of cholecystokinin in regulation of gallbladder function

Quantitative cholescintigraphy using technetium-99m-disofenin was employed to study the kinetics of gallbladder filling and emptying in cats. The radionuclide rapidly visualizes the gallbladder, with activity continuing to rise during the 60 minutes after injection. The gallbladder emptied in a dose-response manner to the intravenous administration of the octapeptide of cholecystokinin (CCK-OP). An infusion of 10 ng/kg/min of CCK-OP resulted in 75% emptying of the gallbladder at 30 min compared to control. This was significantly greater emptying than with an infusion of either 0.1 or 1.0 ng/kg/min. After administration of a fatty meal, the 30-min gallbladder emptying was 73% of control, similar to the response to CCK-OP at a dose of 10 ng/kg/min. Intravenous administration of 1 mg/kg of L-364,718 (a CCK-receptor antagonist) completely inhibited the gallbladder response to a fatty meal but had no effect on gallbladder filling in the fasting state. These results suggest that feline cholescintigraphy can be used for the quantitative study of gallbladder emptying. While CCK appears to be the primary modulator of gallbladder contraction after a fatty meal, no influence of CCK was detected in the interdigestive (fasting) state.