Abstract
Lysosomal membrane lability and enzyme activities were measured in gill and liver tissues of the bluegill sunfish (Lepomis macrochirus). Exposure to sublethal cadmium concentrations for 10 or 21 days resulted in significant increases in the lability of liver lysosomal membranes, as measured by release of N-acetyl-β-D-glucosaminidase (NAG) and acid phosphatase (ACP). Acid phosphatase and NAG activities in liver were decreased by 10 day exposure to cadmium. However, after 21 days of exposure, liver NAG activity was elevated. Cadmium exposure did not affect the lysosomal lability index or the total enzyme activity of lysosomes isolated from gill tissue.In vitro exposure of isolated liver lysosomes to cadmium demonstrated that the increase in membrane lability was not a direct effect of cadmium on the lysosome. Stress induced by crowding the fish had no effect on liver lysosomal membrane lability. Starved bluegill sunfish had significantly destabilized lysosomes, as measured by both NAG and ACP. However, starvation did not affect the total activity of either enzyme. Neither size nor sex had any effect on lysosomal membrane lability, which indicates that field experiments will not be confounded by these factors. The problem of metal bioconcentration in fish has created the need for diagnostic tests which can be utilized to understand the biological effects of these contaminants on fish. The lysosomal membrane lability assay currently holds promise for use as a health monitoring tool.
Published Version
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