The cytotoxicity of microcystin-LR on primary rat hepatocytes and continuous cell lines

Objective The toxicities of microcystin-LR on primary rat hepatocytes and 8 continuous cell lines were investigated to compare their sensitivity to the toxin and to select the appropriate cell lines as models for further study.Method The isolated primary rat hepatocytes and the continuous cell lines were mixed with various concentrations of purified microcystin-LR in 96 well microtitre plates and incubated for 0, 6, 12, 24, 48, 72, and 96 h; meanwhile morphological alterations, colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-dephenyltetrazolium bromide (MTT) assays, lactate dehydrogenase (LDH) release assay were respectively used to evaluate the end point of toxicity.Results Microcystin-LR at level of 5.0 ng/mL exhibited toxic effects on the primary rat hepatocytes after 24 h incubation.Typical S-pattern of dose-response curve for the 48 h incubation hepatocyte with EC_(50) of 5.2 ng/mL was observed and the leakage of LDH from primary rat hepatocytes reached the highest level above 90% at 20 ng/mL of the toxin. Among 8 continuous cell lines, only KB cell line showed reliable significant dose-response effect at toxin concentrations greater than 18.8 μg/mL with 96 h incubation.In KB cells the toxin induced marked morphological alterations at a concentration of about 37.5 μg/mL after incubation for 8 hours and significant amounts of LDH were released from the cells incubated for 72 h at concentrations of 18.8 μg/mL and higher.Conclusion Primary rat hepatocyte is a sensitive cell model for detection of acute toxicity of microcystin-LR and the continuous KB cell line might be suitable for long-term and a little high dose exposure study on the toxin. Other subjected cell lines are not good materials for evaluating cytotoxicity of microcystin-LR.