The influence of liver disease on the methylation of arsenite in humans.

The capacity for inorganic arsenic (ASi) methylation in 13 healthy volunteers and in 30 patients with different types of liver disease has been assessed by measuring the amount of unmetabolized ASi, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) excreted in urine within 24 h after the IV injection of 7.14 micrograms/kg ASi. Liver disease does not affect the percent of the injected dose excreted within 24 h but has striking and opposite effects on the proportions of MMA and DMA. MMA excretion is highly correlated with the 14C-aminopyrine breath test (r = 0.73; P less than 0.05). The reduction in the proportion of MMA excreted in urine and the increase in that of DMA are similar with regard to sensitivity and specificity for detecting liver impairment. Unlike the 14C-aminopyrine breath test, the inorganic arsenic methylation test offers the advantage of being unaffected by treatment with microsomal enzyme inducers.