Influence of dehydrocholate and taurocholate

The influence of dehydrocholate on bromsulphthalein relative-storage capacity, biliary transport maximum (Tm), and fractional transfer rates between plasma, liver, and bile have been studied in unanaesthetized dogs. In six dogs, storage capacity, Tm, and fractional transfer rates from plasma to liver, liver to bile, and liver to plasma were measured during 0-15 M NaCl infusion and the measurements were repeated under a dehydrocholate infusion of 95 ,tmol.min-', ie, an infusion rate approaching the known biliary Tm of bile salts. It was found that: (a) storage capacity and fractional transfer rates from plasma to liver were significantly lower during dehydrocholate infusions (respectively 18-0 + SD 9-0 mg.mg-'. 100 ml-' and 0-120 ± SD 0-035 min-') than during NaCl infusions (respectively 47-0 ± 21-0 mg.mg-1.100 ml-' and 0-280 ± SD 0-055 min-'; P < 0-001); -(b) Tm and fractional transfer rates from liver to bile were also significantly lower during dehydrocholate infusions (respectively 3-2 ± SD 1-1 mg.min-1 and 0-013 ± SD 0-004 min-') than during NaCl infusions (4.8 ± SD 1-1 mg.min-' and 0-033 ± SD 0-017 min-'; P < 0.02); (c) in three additional experiments, taurocholate had similar effects on storage capacity and Tm. These findings suggest that competition occurred between bile salts and bromsulphthalein forhepatic uptake and storage. They support the hypothesis that the decreased disappearance rate and relative storage capacity of bromsulphthalein observed during biliary obstruction may be due to competition between bile salts and bromsulphthalein for hepatic uptake and storage.