Superfund Research Program
Detoxification of Metals: In Vitro and In Vivo Studies
Project Leader: H. Vasken Aposhian
Grant Number: P42ES004940
Funding Period: 1995 - 2000
During the past year, new evidence has been developed which shatters former beliefs about arsenic toxicity. These three equally important results are 1) mono- methylarsonous acid (MMAIII ) is more toxic to human hepatocytes than is inorganic arsenite. This is the strongest evidence that has emerged, which brings into question methylation of inorganic arsenic as a detoxication process. 2) monomethylarsonous acid (MMAIII ) occurs in the urine of some humans chronically exposed to inorganic arsenic in their drinking water. This may indicate a new more selective biomarker for arsenic exposure. 3) the rate limiting enzyme of rabbit liver arsenic biotransformation is MMA(V) reductase. This points out the most crucial step in the methylation of inorganic arsenic.