Protein phosphorylation profile and adduct formation in liver and kidney of microcystin-LR-treated mice

Microcystins are cyclic peptide toxins implicated in several livestock and human deaths. The toxicity of microcystins has been attributed to the highly specific inhibition of serine/theronine protein phosphatases-1 and 2A. Reversible protein phosphorylation is an essential regulatory mechanism in many cellular processes. We aimed to investigate the protein phosphatase inhibition, profile of phosphorylated proteins of serine and threonine residues and microcystin-protein phosphatase adduct in vivo after microcystin-LR exposure by intraperitoneal route in mice. At 1 LD50, there was significant inhibition of protein phosphatases 1 and 2A activity in liver after 30–120 min exposure but there was no effect in kidney. At 0.5 LD50 there was no inhibition of protein phosphatase activity in both liver and kidney. Similarly, time-dependent phosphorylation of serine and threonine residues was observed at 1 LD50. Microcystin-LR—protein phosphatase adduct was time and dose dependent in liver. At 0.5 LD50 the adduct could be detected at 1 and 3 days post-exposure. No adduct could be detected in kidney.