Dependence of the biliary excretion of iopanoic acid on bile salts
Loeb, P.M.; Barnhart, J.L.; Berk, R.N.
Gastroenterology 74(2 Pt 1): 174-181
1978
ISSN/ISBN: 0016-5085 PMID: 620890 Document Number: 129846
The extent to which iopanoate excretion in bile is dependent upon bile salt excretion was investigated in unanesthetized bile fistula dogs. The biliary excretion of iopanoate was studied at 4 different rates of bile salt excretion in separate experiments produced by interruption of the enterohepatic circulation without bile salt infusion and by infusing sodium taurocholate at 3 constant rates (0.48, 1.87, and 3.21 .mu.mol/min per kg). Iopanoic acid was infused in stepwise increasing rates in each of the 4 groups of experiments. The maximum excretion of iopanoate into bile (Emax) was derived from a computer fit of the relation between the biliary excretion rate and plasma concentration of iopanoate for each of the 4 rates of bile salt excretion. The calculated Emax was closely linked to the rate of bile salt excretion. The Emax increased in an apparent linear manner from 0.20 to 2.36 .mu.mol/min per kg as the rate of bile salt excretion increased from 0.21 to 2.62 .mu.mol/min per kg. From the slope of the relation between the biliary excretion of bile salts and the Emax of iopanoate, it could be determined that 0.89 .mu.mol of iopanoate was coupled with each .mu.mol of bile salt. At low plasma concentrations of iopanoate (< 0.06 .mu.mol/ml) when maximum transport of the compound was not obtained, increasing rates of taurocholate infusion did not affect the biliary excretion of iopanoate.