The glutathione S-transferases (GST) play important roles in the detoxification of microcystins (MCs). For better understanding of the responses of GST isforms to MCs exposure, informations about the effects of MCs on GSTs are necessary. In this experiment, we cloned the full length cDNA of 14 GST isoforms (GST alpha, kappa, mu, omega, pi, theta, zeta, and microsomal GST) from Wistar rat. The mRNA abundance of each rat GST isoform in the liver, kidney, and testis was analyzed by real time quantitative PCR. Multiple GST isoforms were constitutively expressed in all examined organs, but some isoforms were expressed at higher level in one organ than in others. The relative changes of the mRNA abundance in the liver, kidney, and testis of Wiatar rat i.v. injected with crude MCs extract at dose of 1LD(50) were also analyzed. Generally, the expression of most GSTs in the liver and testis was suppressed while that in kidney was induced after being injected with MCs. It is suggested that the transcription of GST isoforms varied in different ways within an organ and between organs of Wistar rat exposed to MCs. (c) 2009 Wiley Periodicals, Inc. Environ Toxicol 26: 187-194, 2011.