Cardiotoxic Injury Caused by Chronic Administration of Microcystin-YR

摘要

Microcystins are cyclic peptide toxins.Chronic intoxication with well-known members ofthe microcystin family – microcystins-LR – inducesliver tumour formation, injury of kidney and heart.Despite worldwide distribution in the environment,the effects of microcystins-YR have not been studiedextensively. The aim of the study was to evaluatewhether microcystins-YR, in relatively low doses,have a toxic effect on cardiomyocytes of chronicallytreated rats. Male adult Wistar rats were treatedevery second day for 8 months with microcystins-YR(10 μg/kg i.p., N = 5). Control groups were treatedeither with vehicle (ethanol and methanol 4 : 1 v/v;N = 5) or with physiologic saline (N = 4). The heartsections of microcystin-YR-treated rats revealed decreased volume density of cardiac muscle tissue (microcystins-YR = 0.485 mm3/mm3 ± 0.003; vehicle =0.493 mm3/mm3 ± 0.002; saline = 0.492 mm3/mm3 ±0.002) due to fibrous proliferation. A few lymphocyteinfiltrates were observed. Most of cardiomyocyteswere enlarged (microcystins-YR = 20.19 μm ± 1.34,vehicle = 17.45 μm ± 0.52, saline = 16.00 μm ± 1.43),with enlarged and often bizarre-shaped nuclei anddecreased myofibril volume fraction (microcystinsYR = 0.416 mm3/mm3 ± 0.009; vehicle = 0.472 mm3/mm3 ± 0.009; saline = 0.479 mm3/mm3 ± 0.010). NoTUNEL-positive cells were found in the heart sections of rats in all groups. The results allow the conclusion that chronic exposure to low doses of microcystins-YR may cause atrophy and fibrosis of theheart muscle.