The Distribution and Toxicological Effects of Inhaled Methyl Bromide in the Rat

Abstract

Sixty-day-old male CD rats were exposed by nose only to 14C-methyl bromide (55 ppm) for 3 min. The data indicated that the liver, lung, and kidney were the major organs of 14C distribution immediately after exposure. Up to 32 hr after exposure, the major routes of excretion were pulmonary (14CO2) and renal, with approximately 43% and 21% of the total inhaled radiolabel being eliminated, respectively. In separate experiments, 60-day-old CD male rats were exposed by whole body inhalation for 6 hr/day for 5 and 10 days to 30 ppm methyl bromide or filtered air. Glutathione (GSH) S-transferase and glucose-6-phosphate dehydrogenase (G-6-PDH) activities were increased in the lung. A decrease in GSH-reductase and GSH-S-transferase activities were found in the liver. Serum chemistries indicated a decrease in Cholinesterase, BUN, uric acid, and cholesterol, and leucine aminopeptidase exhibited an increase in activity. These data indicate that methyl bromide is quickly distributed to all tissues after inhalation and rapidly metabolized. A small percentage is cleared slowly and incorporated into metabolic pools, as evidenced by 25% of the initial dose of 14C-methyl bromide found in the rat 32 hr postexposure and the alterations found in hepatic enzyme activities.