Defective blood coagulation is not causative of hepatic haemorrhage induced by microcystin-LR

Male rats were intraperitoneally administered a lethal dose of microcystin-LR (a toxin of cyanobacteria). Prior to haemorrhage in the liver, blood coagulation and platelet aggregation activities were measured. The number of cellular components, white blood cells, red blood cells and, especially, platelets, decreased 1-1.5 hr after the injection. Plasma kaolin-activated partial thromboplastin time was prolonged and fibrinogen concentration was reduced, but antithrombin III activity and fibrin degradation product concentration were not significantly changed. Platelet aggregation was not affected for up to 0.5-1.0 hr after administration. Sequential analyses of those parameters and hepatotoxic markers indicate that those hematologic changes as well as the hepatic injury occur suddenly after the massive bleeding. These results suggest that microcystin-LR does not directly act on the haemostatic system to cause a disseminated intravascular coagulation-like state. The decrease in blood coagulation activity and platelet particle concentration may be the results of secondary consumptive effects following the hepatic haemorrhage.