Studies with chlorambucil I. Effect on lactate dehydrogenase in the testes of albino rabbits treated with multiple doses of chlorambucil

Treatment with multiple sub-lethal doses of chlorambucil resulted in lower activity levels ad specific activity of LDH and low protein content in the testes of albino rabbits. Electrophoretic analysis and assay of individual isozymes eluted from DEAE-Sephadex A-50 indicated that this loss in activity was related to the differential and/or selective action of chlorambucil on LDH4, which was affected most, while LDH3 and LDH5 were affected to a lesser degree. Kinetic inhibitory studies on purified rabbit muscle LDH in vitro revealed that chlorambucil in the reaction mixture binds to non-active enzyme sites resulting in non-competitive irreversible inhibition of LDH.