Gallbladder contractility in aspirin- and cholesterol-fed prairie dogs

Whether aspirin prevents cholesterol gallstone formation is controversial. This study aimed to investigate this issue and determine the depression of gallbladder smooth muscle contractility associated with cholesterol feeding in the prairie dog.

Prairie dogs were divided into four subgroups. Animals were fed control or 1.2% cholesterol diet and treated with placebo or aspirin for 2 weeks. The presence of crystals and stones was determined, and contractile force in response to cholecystokinin octapeptide (CCK-8) of gallbladder muscle strips was measured.

Maximal stress of 2.66 +/- 0.23 x 10(4) N/m2 was measured in muscle strips from animals on control diet. Maximal stress was significantly lower in strips from animals on high-cholesterol diet, being 1.49 +/- 0.16 x 10(4) N/m2 with placebo and 1.62 +/- 0.23 x 10(4) N/m2 with aspirin. The difference in maximal stress between aspirin-treated and placebo-treated animals was not significant. Although none of the animals on control diet had crystals or stones, all animals on the high-cholesterol diet, whether receiving placebo or aspirin, had crystals in the bile, and more than 65% had cholesterol stones.

Aspirin has no effect on stone formation, nor does it prevent the decrease in contractility despite a profound decrease in endogenous gallbladder prostanoid synthesis.