Time course of the effect of OA, MC-LR and MeOk on glucose uptake in Clone 9 hepatocytes. 2-NBDG was added to cells at a final concentration of 500 µM, and fluorescence inside the cells was measured for 30 min, every 5 s. Effect of 1.5 µM OA (A), 1.5 µM MC-LR (B), 1.5 µM MeOk (C), 15 µM MeOk (D) or vehicle (control) was evaluated. Results are presented as mean ± SEM of n= 4 experiments. *P < 0.05; **P < 0.01, significantly different from control; Student's t-test. 2-NBDG, 2-{N-[7-nitrobenz-2-oxa-1, 3-diazol 4-yl] amino}-2-deoxyglucose; A.U., arbitrary units; MC-LR, microcystin-leucine and arginine; MeOk, methyl okadaate; OA, okadaic acid.