Hepatic and extra-hepatic glutathione-S-transferase activity in wild pigeons (Columba livia).

ABSTRACT

Glutathione-S-transferase (EC 2.5.1.18) activity was assayed in hepatic and extrahepatic tissues of pigeons using l-chloro-2,4-dinitrobenzene and l,2-dichloro-4-nitrobenzene as substrates. Gluthathione-S-transferase activity towards l-chloro-2,4-dinitrobenzene in pigeon was in the order kidney >liver >testes >brain >lung>heart. The enzyme activity with 1- chloro-2,4-dinitrobenzene as substrate was 40-44 times higher in pigeon liver and kidney than that observed with l,2-dichloro-4-dinitrobenzene as substrate. Km values of hepatic and renal glutathione transferase with l-chloro-2,4-dinitrobenzene as substrate were 2.5 and 3 mM respectively. Double reciprocal plots with varying reduced gluthathione concentrations resulted in biphasic curves with two Km values (liver 0.31 mM and 4mM; kidney 0.36 mM and 1.3 mM). The enzyme activity was inhibited by oxidized gluthathione in a dose-dependent pattern. 3-Methylcholanthrene elicited about 50% induction of hepatic glutathione transferase activity whereas phenobarbital was ineffective.