Acute toxicity of Microcystis aeruginosa and its cardiovascular effects.

The acute toxicity of a water extract from unialgal-cultured blue-green alga Microcystis aeruginosa M228 on mice and rats was studied. The mice intraperitoneally injected with the extract became lethargic and piloerection was seen. Terminally their ears, tails, limbs, and eyes became chalky white. The LD50 value of the extract for mice was estimated at 14.4 mg dry wt of cells/kg and that of rats was 67.4 mg/kg. Tachycardia was shown in the mice injected with the extract. A value of LD50 of coadministration of the extract and phenoxybenzamine in mice was significantly larger than that of the extract alone and survival time of mice injected with the extract and phenoxybenzamine was prolonged. These results suggest that the extract of the alga may take the acute toxic effects via the sympathetic nervous system.