Effects of OA (A), MC-LR (B) and MeOk (C) on metabolic rate in Clone 9 hepatocytes after 24 h incubation. 1D shows the effect of 1.5 µM OA or 15 µM MeOk on the metabolic rate of BE(2)-M17 human neuroblastoma cells after 24 h of treatment. Results are presented as percentage of Alamar Blue fluorescence relative to control cells (100%); mean values ± SEM, with n= 3. *P < 0.05; **P < 0.01, significantly different from control; Student's t-test. MC-LR, microcystin-leucine and arginine; MeOk, methyl okadaate; OA, okadaic acid.