Homogenized milk: is it really the culprit in dietary-induced atherosclerosis?

Xanthine oxidase activity was assayed in commercial samples of homogenized milk subjected to pH ranging from 6.7 to 2.0 and held at room temperature for 5 min. Activity decreased sharply between pH 5.5 and 3.2. Below pH 3.2 no activity was detected. Also, rabbit anti-bovine xanthine oxidase failed to crossreact immunologically with xanthine oxidase of mouse milk. These results cast doubt on the hypothesis that dietary xanthine oxidase participates in the formation of atherosclerotic plaques.