Effect of tauroursodeoxycholate on the biliary transport maximum of sulfobromophthalein in the rat

The effect of tauroursodeoxycholate (TU) infusion on the plasma level and biliary transport maximum (Tm) of sulfobromophthalein (BSP) was examined in male rats during a continuous intravenous infusion of BSP with different TU infusion rates. The infusion rate of 0.6 mumol/min/100 gm body weight of TU caused significantly higher bile flow and BSP Tm values compared with the respective control values in rats with only a BSP infusion. These values, however, were significantly lower than values obtained by an equimolar infusion of taurocholate (TC). The higher infusion rates of TU (1.2 and 1.8 mumol/min/100 gm) tended to cause higher bile flow rates, but the BSP Tm value did not increase beyond the value obtained at the lower infusion rate (0.6 mumol/min/100 gm). In the highest TU infusion rate study (1.8 mumol/min/100 gm), plasma BSP concentrations were significantly higher than corresponding control values or values at a lower TU or TC infusion rate. It was concluded that in rats TU can significantly increase the BSP Tm, but to a lesser extent than TC. Furthermore, it was suggested that TU infusion at a higher rate significantly interferes with the hepatic uptake (or storage) of BSP.