Expression and activity of arsenic methyltransferase Cyt19 in rat tissues

Arsenic has been reportedly metabolized by the repetitive reduction and methylation, and is excreted mainly in urine as methylated arsenicals such as monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV). Although it has been demonstrated that the methylation of arsenic is catalyzed by arsenic methyltransferase, Cyt19, very little is known about the characteristics of this enzyme. We investigated mRNA and protein levels of Cyt19 and the enzyme activity of Cyt19 in rat tissues by Northern and Western blottings and high-performance liquid chromatography–inductively coupled argon plasma mass spectrometry (HPLC–ICP MS). Both mRNA and protein levels of the liver were higher than those of other tissues. An intermediate expression of Cyt19 mRNA was observed in the heart and testis. Methylated arsenicals were found to be produced by the liver cytosol using the current HPLC–ICP MS method.