EPA Science Inventory

Arsenic (+3 oxidation state) methyltransferase and the methylation of arsenicals in the invertebrate chordate Ciona intestinalis

Citation:

Nava, G. M., S. Cai, J. L. Boyer, A. Hernandez-Zavala, D. J. THOMAS, AND H. R. Gaskins. Arsenic (+3 oxidation state) methyltransferase and the methylation of arsenicals in the invertebrate chordate Ciona intestinalis. TOXICOLOGICAL SCIENCES. Society of Toxicology, 113(1):70-76, (2009).

Description:

Biotransformation of inorganic arsenic (iAs) involves methylation catalyzed by arsenic (+3 oxidation state) methyltransferase (As3mt), yielding mono- , di- , and trimethylated arsenicals. To investigate the evolution of molecular mechanisms that mediate arsenic biotransformation, a comparative genomic approach focusing on the invertebrate chordate Ciona intestinalis, was used. Bioinformatic analyses identified an As3mt gene in the C. intestinalis genome. Constitutive As3mt RNA expression was observed in heart, branchial sac and gastrointestinal tract. Adult animals were exposed to zero or 1 ppm of iAs for 1 or 5 days. Steady-state As3mt RNA expression in the gastrointestinal tract was not modulated significantly by 5 days of exposure to iAs. Tissue levels of iAs and its methylated metabolites were determined by hydride generation-cryotrapping-gas chromatography-atomic absorption spectrometry. At either time point, exposure to iAs significantly increased concentrations of iAs and its methylated metabolites in tissues. After 5 days of exposure, total speciated arsenic concentrations were highest in branchial sac (3705 ng/g) followed by heart (1019 ng/g) and gastrointestinal tract (835 ng/g). At this time point, the sum of the speciated arsenical concentrations in gastrointestinal tract and heart equaled or exceeded that of iAs; in branchial sac, iAs was the predominant species present. Ciona intestinalis metabolizes iAs to its methylated metabolites, which are retained in tissues. This metabolic pattern is consistent with the presence of an As3mt ortholog in its genome and constitutive expression of the gene in prominent organs, making this basal chordate a useful model to examine the evolution of arsenic detoxification. This is a brief article on recent work on the capacity of a primitive chordate, Ciona intestinalis, to methylate inorganic arsenic.

Purpose/Objective:

To study the orthologous AS3MT gene and its the funciton in arsenic methylation

URLs/Downloads:

TOXICOLOGICAL SCIENCES   Exit

Record Details:

Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Start Date: 01/01/2010
Completion Date: 01/01/2010
Record Last Revised: 02/04/2010
Record Created: 12/18/2007
Record Released: 12/18/2007
OMB Category: Other
Record ID: 187749

Organization:

U.S. ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF RESEARCH AND DEVELOPMENT

NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LAB

EXPERIMENTAL TOXICOLOGY DIVISION

PHARMACOKINETICS BRANCH