Adenosine triphosphatase in the microsomal fraction from rat brain.

2. The nuclei in vitro incorporate [2-14C]glycine and [1-14C]valine into nuclear protein and [6-14C]orotic acid and [8-14C]adenine into nucleic acids. 3. Anoxia and 2,4-dinitrophenol inhibit the incorporation of the radioactive precursors into nuclear proteins and nucleic acids. Chlorpromazine inhibits the incorporation of valine, but has no effect on the incorporation of orotic acid. 4. The specific activities of adenosine triphosphatase, succinoxidase, cytochrome oxidase,DPNHcytochrome c reductase, DPNH-neotetrazolium reductase and lactic dehydrogenase are reported. Evidence suggesting that succinoxidase activity isdue to mitochondrial contamination whereas cytochrome oxidase is a true nuclear component is presented. 5. The chemical composition and metabolism of rat-kidney nuclei and rat-liver nuclei are compared.