Liver Xanthine Oxidase and Qo 2 in Relation to Thyroid Activity ∗

Abstract

Summary

The Qo₂ of a liver slice, in contrast to an homogenate, was relatively independent of the xanthine oxidase activity of the liver, since the latter could be varied widely by dietary procedures without affecting the former.

Thyroxine increased the liver slice Qo₂ of rats fed stock chow, a purified 21% casein diet, or a purified 8% casein diet; no hyperthyroidal exhaustion of the liver Qo₂ could be produced.

Thyroxine had no effect on liver xanthine oxidase when rats were fed a purified 21% casein diet, but tended to give higher values with chow-fed adult rats. When administered with a low protein diet, thyroxine prevented the marked depletion of liver xanthine oxidase and gave results more characteristic of starvation than of a low protein diet.

Growth hormone and ACTH had no effect on liver xanthine oxidase.