Azoproteins of liver nuclei isolated in an aqueous or nonaqueous medium from rats fed an azocarcinogen.

The proteins and azoproteins of liver nuclei isolated in aque ous or nonaqueous medium from livers of rats fed the hepato carcinogen 3'-methyl-4-dimethylaminoazobenzene for 20 days were compared. The two types of nuclear preparation ap parently contained similar quantities of saline-soluble and-insoluble protein-bound azo dyes. in aqueous nuclei, the pro tein-bound dyes represent only 3% of those in liver, were 86% saline-soluble, and were present at a concentration (per mg protein) 43% that in cytoplasm. One-half of the proteins of both nuclei were saline-soluble and were similar according to free boundary and column zonal electrophoresis. In contrast to the situation with aqueous nuclei, which contain sizeable amounts of the specific soluble azoproteins, little of these slow h2-like azoproteins were found in the nonaqueous nuclei. The possible basis of this difference is discussed.