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

The hepatic cytochrome P-450 microsomal mixed function oxidase system that plays a major role in the metabolism of many endogenous and foreign compoun ds is one of the several liver functions impaired in total bile duct obstru ction. However, no information existed concerning to the function of this s ystem in incomplete bile duct stenosis, as seen in man in chronic pancreati tis, 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 lime. In the present study, the microsomal mixed-function oxidase act ivity was tested in rats with incomplete mild stenosis of the common bile d uct, by following weekly the aminopyrine breath test up to three weeks of e volution. The bile duct stenosis was evident from the increase of the bilia ry pressure, upstream dilatation of the bile duct, and ductular proliferati on. Thus leaving the conduct intact, this model simulates a compression or constriction of the bile duct at early stages. The results showed a decreas e in the peak of the exhalation and a lengthening of the half time of elimi nation of (CO2)-C-14 from the metabolized C-14-aminopyrine that was injecte d, which were restored by the third week. This pattern was rather similar t o 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 duc t. Likewise hepatic adaptive changes could support its recuperation. (C) 19 99 Elsevier Science Ireland Ltd. All rights reserved.