Experimental Studies on the Effects of Certain Organic Anions upon the Exeretion of Bilirubin

Abstract

The effects of several organic anions on Bilirubin excretion were studied in rats with biliary fistula, and the following results were obtained.
1) Pretreatment of rats with phenobarbital increases excretion of endogenous as well as exogenous bilirubin. A study with ³H-delta-aminolevulinic acid has suggested an increase of biliary ³H-bilirubin in an early pnase of the administration of the former, and hence increase of early labeled bilirubin. Increased biliary excretion of unconjugated bilirubin load was seen only shortly after the administration.
2) Novobiocin inhibited the biliary excretion of bilirubin, suggesting an inhibition in the process of bilirubin excretion. The effect was rather short, but competition as substrate for excretion seems rather unlikely.
3) A mutual inhibition for excretion is obvious between BSP and bilirubin. The biliary excretion of BSP was markedly reduced by coadministration of bilirubin, and the reduction was most pronounced in the fraction of nonconjugate BSP during the early phase of administration.
The same was true with ¹³¹I-BSP. These results indicate that the biliary excretion of bilirubin as a function of hepatocyte is influenced by a number of organic anions and various mechanisms during the transport in the cell, which involves several biochemical processes.