Effect of subchronic dietary administration of butylated hydroxyanisole on canine stomach and hepatic tissue.

Beagle dogs, 29 males and 30 females, were assigned to feeding groups of 0, 1.0 and 1.3% butylated hydroxyanisole (BHA) for 180 days. Animals were observed daily for physical signs of pharmacological or toxicological effect. Except for the production of a reddish-brown urine, no physical signs attributable to BHA administration were observed. Both food consumption and body-weight gain were reduced in the BHA-treated animals. Fifty-one animals completed the study. At termination, tissues were examined for gross BHA-related effects, and specimens were taken for enzyme analysis, light microscopy, electron microscopy and morphometric analysis. The liver showed a significant weight increase over the control in both sexes at both BHA dose levels. Ultrastructural examination of the liver of BHA-treated animals revealed proliferation of smooth endoplasmic reticulum and hepatocytic cytoplasmic myelinoid bodies. Enzyme analysis of hepatic tissue showed a significant increase in mixed-function oxidases, UDP glucuronyl transferase, glutathione S-transferase and epoxide hydratase in the BHA-treated dogs compared with the controls. Light microscopy revealed no proliferative/hyperplastic lesions of the stomach/gastric epithelium. Electron microscopic examination of the lower oesophagus and stomach specimens from representative animals from each treatment group failed to reveal any treatment-related effect as compared with controls.