Microcystins (MCs) are a group of widely characterized cyclic heptapeptides able to induce a series of liver injury, including acute liver failure and primary liver cancer.Although the dualistic effects of MCs have been postulated, the specific action mode and the possible mechanisms according to the exposure dosage of MCs remain unknown.Thus in the present study, the primarily cultured rat hepatocytes was used to systematically investigate the hepatotoxic characteristics of MC-LR (one of the most abundant and toxic MCs variants).