Relative oral toxicity of eight common microcystin congeners in mice

Session: Poster Session

Donna Hill, US EPA, [email protected]
Neil Chernoff, US EPA, [email protected]
Johnsie Lang, US EPA/ ORISE, [email protected]
Judy Schmid, US EPA, [email protected]

Abstract

Microcystin-LR is the most common cyanotoxin and microcystin (MC) in US freshwater harmful algal blooms (HABS), yet there is limited animal toxicology that can be applied towards developing human health guidelines.  Eight microcystin congeners (MCLR, MCRR, MCLA, MCLY, MCLF, MCLW, MCWR, MCYR) were administered by gavage to male and female BALB/c mice at a single dose of 7mg/kg for comparison to the MCLR hepatic toxicity that occurs with this dose. Animals were monitored and euthanized 24 hours later for necropsy. Gross liver appearance scores, and serum chemistries for liver and kidney function were measured.  Based on serum markers for liver toxicity and gross liver appearance, four of the congeners produced little to no difference from controls at this dose:  MCRR, MCLF, MCLW, and MCWR.  The remaining compounds produced toxicity in the order of MCLA>MCLR>MCLY>MCYR.  Our relative toxicity results differed from previous in vitro predictions based on relative hydrophobicity or cell death using protein phosphatase inhibition. ELISA tests for MC content in environmental waters produce values for total MCs that are often converted to MCLR equivalents to determine potential toxicity. These results indicate a need to have a rapid measurement of specific MC congeners so HAB toxicity is not over- or under-estimated. 

Does not represent EPA policy.