Pharmacokinetic studies of biliary excretion. IV. The relationship between the biliary excretion behavior and the elimination from plasma of azo dyes and triphenylmethane dyes in rat.

Abstract

The relaionship between the biliary excretion behavior and the elimination from plasma was studied using the same series of azo and triphenylmethane dyes in the previous papers in rat. Amaranth (AM) and new coccine (NC) in azo dyes, and Brilliant blue FCF (BB) and light green SF (LG) in triphenylmethane dyes, were used for the comparison. In azo dyes, the plasma elimination constants of NC, 0.034×10-1min-1 was almost three times samller than that of AM, 1.19×10-1min-1, but the elimination curves were considered similar with each other. And the difference of the binding ratio with plasma protein was only 10%. It was suggested that the remarkable difference of the biliary excretion behaviour between AM and NC, did not depend on the first step in the blood and that there were some other factors such as uptaking into liver celles, urinary excretion, metabolism and so on. As for triphenylmethane dyes, the plasma elimination of BB was remarkably rapid and it's half life was about 2.8 min. And it was of interest that the bile to plasma concentration ratio reached more than 500 at 15 min after intravenous injection. The elimination of LG was very slow and it's half life was about 40 min and 15 times lager than that of BB. And the binding ratio of LG was 2.5 times larger than that of BB. It was concluded that the remarkable difference of biliary excretion between BB and LG depended mainly upon the difference of binding ratio with plasma protein and slow disappearance from blood of LG.