ABSTRACT
Cyanobacteria (Microcystis aeruginosa), which produce powerful hepatotoxic cyclopetpides, were collected and submitted to the determination of toxicity through intraperitoneal injections made in 30 and 90 days-old Swiss albino mice. The liver and the spleen were histopathologically analyzed and the weight and vital signs development were monitored. Test of toxicity resulted in a LD 50 of 154.28 mg.Kg -1 . M.aeruginosa represented 95 (per cent) of the analyzed biomass. The ratios between liver weight and body weight in the animal inoculated with a single dose were 6.0 (per cent) and 7.2 (per cent), with multi doses 7.0 (per cent) and 7.5 (per cent) and in the control animals 4.0 (per cent) and 5.0 (per cent), for adult and young animals, respectively . There was an accentuated increase in the volume and weight of the spleen, and the animals inoculated with a single dose showed a ratio between spleen weight and body weight of 0.67 (per cent) and 0.37 (per cent), with multidoses 1.22 (per cent) and 1.05 (per cent) and the control animals the ratio was 0.12 (per cent) and 0.15 (per cent), for adult and young animals, respectively. The young animals inoculated with single and multi doses had an increase of 150 (per cent) and 407 (per cent) in the spleen size while the adults increased, 607 (per cent) and 845 (per cent), respectively, in relation to the control. The histopathological analysis showed strong differences in the structure of the hepatic parenchyme in control animals and in those exposed to the M.aeruginosa extract. The main alterations were the congestive aspect, including the sinusoid, and intrahepatic haemorrhagia. The histopathological analysis showed considerable increase in the number of multinuclear giant cells in the spleen of the animals intoxicated by M.aeruginosa.