Effect of microcystin-LR on protein phosphatase activity in fed and fasted juvenile goldfish Carassius auratus L.

Fed and fasted juvenile goldfish Carassius auratus (30 g body weight) were injected intraperitoneally (i.p.) with microcystin-LR (MC-LR) (125 microg/kg body weight) to determine the effect of alimentary status on the hepatic toxicity of MC-LR. The toxin accumulation pattern was similar in both fed and fasted treatments. MC-LR accumulated during the first 48 h post-injection and decreased significantly between 48 and 96 h. MC-LR accumulation induced a decrease in hepatic protein phosphatase activity and glycogen content. Fasted individuals were more severely and more rapidly affected than fed ones. Both indicators were significantly altered after 6 h of fasted treatment. In particular, protein phosphatase activity was totally inhibited after 6 h in the fasted treatment but only lowered and not totally suppressed in the fed one. In both treatments, the recovery of enzyme activity was complete after 96 h. On the other hand, hepatic glutathione concentration and glutathione S-transferase activity were not significantly affected.