Effect of Zinc and Mercury on Lysosomal Membrane Stability of the Fish Oreochromis mossambicus (Peters)

Lysosomal enzyme release assay technique was carried out in the fish Oreochromis mossambicus exposed to mercury, a non-essential heavy metal, and zinc, an essential heavy metal. Mercury has an initial stabilizing effect on the lysosomal membrane followed by a progressive labilization indicating that sequestration of mercury by lysosomes, which relieves the biochemical machinery from the toxic effects, is efficient only up to a certain limit. Thereafter, the detoxifying machinery becomes ineffective resulting in the decline of the structure linked latency of lysosomal enzymes. On exposure to zinc, an initial labilization is seen probably due to the delayed onset of operation of the detoxifying mechanisms against this essential metal. Continued exposure to zinc stabilizes the membrane either by binding to the structural components or by inhibiting metal catalysed lipid peroxidation. Lysosomal enzyme release assay (LERA) is, thus, effective as a sensitive index of heavy metal stress and can be applied as a biochemical warning of environmental alterations.