The relationship of the BSP retaining capacity of organic anion binding protein in the liver to the transport of BSP from plasma to bile was examined in CCl
4-treated rats. These proteins were separated into Iigandin and Z protein by Sephadex G-75 gel chromatography. The BSP retaining capacity of these proteins was significantly decreased by CCl
4 administration (2.5 ml/kg, p.o.). At 3 hours after CCl
4, this decreased capacity was caused mainly by the decrease in their binding affinity, at 24 hours after CCl
4, however, it was accompanied by decreases in both their binding affinity and protein amounts. At 3 hours, the hepatic uptake of BSP evaluated by determination of plasma BSP concentration, the initial disappearance rate (K
1), and the hepatic dye content did not differ from those in the controls, and biliary excretion of BSP was unchanged. At 24 hours, hepatic uptake and biliary excretion of BSP as well as bile flow were significantly decreased. From these results, it is suggested that the alteration in the retaining capacity of ligandin and Z protein would not be a determinant factor in the transfer of BSP from plasma to bile.
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