Increased biliary excretion of ouabain induced by bucolome in the rat

1. Following the intravenous injection of 3H-ouabain (0.4 or 0.6 mg/100 g body weight) the plasma concentration and biliary excretion of ouabain were compared for control male Wistar rats and rats given bucolome (BC, 1-cyclohexyl-5-n-butyl-2,4,6-trioxoperhydroxypyrimidine, 20 mg/100 g) 40 min before the ouabain injection. In bucolome treated rats, the bile flow rate was 80-90% higher than in control rats and the biliary excretion rate of ouabain for the 40 min post-injection period was significantly higher in bucolome treated rat groups. The increase was due to an approximately two-fold increase in the excretion rate in the first 10 min period. On the other hand, plasma concentration of ouabain was significantly higher in bucolome treated rats compared with control rats at corresponding time intervals. Plasma volume as determined by 131I-labelled albumin dilution was not decreased in bucolome treated rats. 2. The results indicated that the significant increase in biliary excretion of ouabain administration was due to the enhancement of the hepatic transport and/or biliary excretion process and not due to an increase in hepatic uptake.