Comparison of the sublethal effect of mercury and lead on visceral dehydrogenase system in three inland teleosts.

The sublethal effect of mercury and lead was investigated on visceral (liver, muscle, gill, kidney and brain) succinic, malic and lactic dehydrogenases in Labeo rohita, Clarias batrachus and Chana punctatus in acute experiments. The highest decrease of succinic, malic and lactic dehydrogenases was recorded in the hepatic tissue in comparison to muscle, brain, kidney and gill. This decrease was greater in L. rohita than in C. batrachus or in C. punctatus. Mercury was more effective than lead. Marked variations in the activities of the three dehydrogenases in dark tissues (liver, kidney) were noted after exposure to mercury than lead in the above mentioned species. The observed dehydrogenase variations are discussed in relation to the breakdown of gas exchange at the lamellar level, to visceral hypoxia, hypoglycaemia, impaired aerobic and anaerobic pathways, formation of a metalloenzyme complex and alterations in mitochondrial electron transport.