Distribution of microcystin-LR to testis of male Sprague-Dawley rats.

Microcystins (MCs) are a group of cyclic heptapeptide toxins produced by naturally freshwater cyanobacteria. Among more than 90 identified analogues of microcystins, microcystin-LR (MC-LR) is the most abundant and toxic. Our previous investigations indicated that MC-LR displays male reproductive toxicity, but the target of MC-LR in testes remains unclear. To this end, the present study is designed to elucidate whether microcystin-LR could be distributed to testes and explore the target cells in testes. In the in vivo study, male Sprague-Dawley rats were injected intraperitoneally with MC-LR at a dose of 300 μg/kg per day for 6 days. MC-LR was detected in testes, mainly within seminiferous tubules, which was further validated by Western blot. The concentrations of MC-LR were determined by LC-MS analysis, with a result of 0.0252 ± 0.0037 and 0.0056 ± 0.0012 μg/g dry weight in liver and testis respectively. In the in vitro study, Primary cultured spermatogonia, Sertoli cells and Leydig cells were exposed to MC-LR respectively, and MC-LR was observed to enter spermatogonia and Sertoli cells, but not Leydig cells. These results suggested that the reproductive toxicity of MC-LR were induced by its distribution in testis. Spermatogonia and Sertoli cells are important target cells.