ENZYMATIC ANALYSIS OF LIVER SAMPLES FROM RAINBOW-TROUT FOR DIAGNOSIS OF BLUE-GREEN ALGAE-INDUCED TOXICOSIS

Microcystin and related toxic peptides produced by cyanobacteria (blue -green algae) are potent and selective inhibitors of protein phosphata ses 1 and 2A. We adapted existing enzymatic techniques to analyze the liver of rainbow trout after oral administration of hepatotoxic cyanob acteria. Liver tissue was removed 3 and 12 hours after treatment, and phosphatase activity was determined in liver extracts, using a specifi c phosphoprotein substrate. In all samples from fish exposed to toxic cyanobacteria, phosphatase activity was suppressed, whereas the contro l enzyme, lactate dehydrogenase, present in the same liver extract, wa s not affected by cyanobacteria. Thus, experimental poisoning by hepat otoxic cyanobacteria resulted in an abnormally low ratio of phosphatas e to lactate dehydrogenase activity in the liver extracts. These resul ts indicate that specific inhibition of phosphatases 1 and 2A may prov ide a useful diagnostic tool to determine the early effects of cyanoba cteria toxic peptides directly in liver samples from poisoned animals. Although this test was developed with rainbow trout, it should be pos sible to extend the analysis of liver phosphatase activity to other sp ecies, including sheep and cattle, which are frequently affected by he patotoxic cyanobacteria.