The aminopyrine breath test (ABT) in a rat model of incomplete stenosis of the common bile duct

Abstract

The hepatic cytochrome P-450 microsomal mixed function oxidase system that plays a major role in the metabolism of many endogenous and foreign compounds is one of the several liver functions impaired in total bile duct obstruction. However, no information existed concerning to the function of this system in incomplete bile duct stenosis, as seen in man in chronic pancreatitis, early stages of tumorous lesions of the common bile duct or in primary sclerosing cholangitis, in which the clinical features could be poor for a long time. In the present study, the microsomal mixed-function oxidase activity was tested in rats with incomplete mild stenosis of the common bile duct, by following weekly the aminopyrine breath test up to three weeks of evolution. The bile duct stenosis was evident from the increase of the biliary pressure, upstream dilatation of the bile duct, and ductular proliferation. Thus leaving the conduct intact, this model simulates a compression or constriction of the bile duct at early stages. The results showed a decrease in the peak of the exhalation and a lengthening of the half time of elimination of 14CO 2 from the metabolized 14C-aminopyrine that was injected, which were restored by the third week. This pattern was rather similar to that of serum bilirubin, which after an initial increase then returned to basal values. The study suggested that aminopyrine breath test, considered a measurement of the demethylase activity of the microsomal mixed function oxidase system, may be impaired in the incomplete stenosis of the bile duct. Likewise hepatic adaptive changes could support its recuperation.