The effects of phenylhydrazine and cobalt chloride on the electrophoretic and isoeletric focusing behaviour of some enzymes in Clarias gariepinus (Clariidae, Teleostei)

1. The electrophoretic and isoelectric focusing behaviour of the LDH, MDH and GPI isozymes of seven tissues was compared for several examples of Clarias gariepinus. 2. Some specimens were injected with phenylhydrazine, others with cobalt chloride while the remaining untreated specimens constituted the normal controls. 3. A significant decrease in, or even the total disappearance of, the activity of the different isozymes considered was found in some tissues from specimens subjected to phenylhydrazine. 4. These results were then correlated to the following: specific enzyme and tissue activity; aerobic or anaerobic metabolism; the nature of the toxic contaminant; hepatic lipogenesis as a defence mechanism in fish; and carbohydrate metabolism.