Microcystin RR is a cyclic heptapeptide initially produced by species of cyanobacteria Microcystis. Microcystin RR exhibits cytotoxic, pro-oxidative, and carcinogenic properties. Microcystin RR induces endocrine disruption and alters cholesterol synthesis and lipid oxidation in vivo. Additionally, Microcystin RR induces mitochondrial dysfunction and oxidative stress, altering gonadal structure in development. In other animal models, Microcystin RR alters levels of Bcl-2, Bax, p53, and GRP78, inducing apoptosis and liver damage.