SULFATE AND GLUCURONIDE CONJUGATES OF BILIRUBIN IN EXPERIMENTAL LIVER INJURY*

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Abstract
Rats, including those with bile fistulas and isolated perfused liver systems, were utilized for the study of sulfate and glucuronide conjugates of bilirubin. The experimental conditions entailed exposure to carbon tetrachloride and ligation of the common bile duct for short and long periods followed by intra-peritoneal injection of inorganic s35()4. Pigments I and II of bile or plasma were separated and estimated by the technic of reversed-phase partition chromatography. The pigments were diazotized, purified further by chemical partition, and placed on paper chromatographic systems for radioautography and analysis. With acute obstruction to bile flow, pigment II was the predominant conjugated pigment in the plasma. With added CCI4 injury or with prolonged biliary obstruction, the proportion of pigment I in the plasma increased. Sulfate conjugate of bilirubin was not associated with pigment I, but was found with the glucuronide in pigment II. Incubation with B-glucuronidase permitted the separation of glucuronide from sulfate when chromatographed on paper. After ligation of the common bile duct for a short period (24 hours), approximately the same proportion of bilirubin sulfate appeared in the pigment II fraction of the jaundiced plasma as is ordinarily present in normal bile. With added CCI4 exposure or after prolonged obstruction, the relative amount of serum bilirubin conjugated as a sulfate increased. Carbon tetrachloride exposure also caused a relative increase in the sulfate conjugate of bilirubin in the bile. This increase was accompanied by a decrease in the proportion of bilirubin conjugated as the diglucuronide. With CCI4 injury a significant decrease in the molar ratio of glucuronide to bilirubin was demonstrated in the bile. Studies with the isolated perfused rat liver system indicated that formation of bilirubin sulfate depended on an intrahepatic mechanism, although extrahepatic formation was not excluded. In the isolated liver, these altered proportions of sulfate and glucuronide conjugates in response to CCI4 injury are not functions of differing renal thresholds for these substances.