Subacute Inhalation Experiment for Methyl Bromide in Rats

Abstract

Male rats were exposed to four different concentrations of methyl bromide for 4 hrs/day ; 150 ppm for 11 weeks, 55 times, and to 200, 300, and 400 ppm for 6 weeks, 30 times. Changes in body weight, general condition and hema-tology, changes in organ weight, residual bromide ion concentration, and histopa-thology of several organs were studied. Suppression of body weight increment, abnormal clinical signs and severe weakness were found in the highly exposed group. Bromide ion accumulation was seen especially in the kidney and spleen, without significant dose-related change.
Remarkable changes appeared histopathologically in the brain and heart. Necrosis was exhibited zonally from the first to fourth layers of the dorso-external cortex bilaterally, showing a spongy, edematous and hyperemic appearance, accompanied by proliferation of blood vessels. This bilateral lesion had spread selectively to basal nuclei and brain stem. Multiple, small focal necroses were found in wide regions of the heart. Necrosis of the brain and heart, both of which have high sensitivity to oxygen defficiency, was thought to be caused by the longterm hypoxic condition as manifested in the histopathological findings.