A comparison of cell nuclei isolated from rabbit tissues by aqueous and non-aqueous procedures

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Abstract
A description is given of a modified method for the preparation of rabbit cell nuclei in nonaqueous media. Such non-aqueous nuclei (NAN), which retain their water-soluble constituents, are compared with nuclei (CN) isolated by the conventional citric acid method. On a percentage basis NAN have a much lower content of desoxyri-bonucleic acid (DNA) than CN have, but their content of ribo-nucleic acid (RNA) is slightly higher. The protein content of NAN lies between 79 and 92% and is considerably higher than that of CN (66-72%). In experiments on the incorporation of radioactive P into the cell nuclei of rabbit tissues, the specific activity of DNA was the same in NAN as in CN in all tissues examined except intestinal mucosa where, 2 hours after administration of P32, it was invariably higher in NAN than in CN. Activity of nuclear RNA was higher in CN than in NAN in all tissues examined. When NAN was treated with citric acid in conditions similar to those obtaining in the isolation of CN, no DNA was removed, but 14-23% of the protein content was extracted, together with about half the RNA. The RNA so removed had a specific activity considerably lower than that of the RNA which remained. The implications of these observations are discussed, and it is concluded that the RNA of the cell nucleus is heterogeneous in nature, a considerable proportion being lost in a conventional preparation of nuclei from aqueous media. Such nuclei are thus inadequate for a complete study of nuclear metabolism.
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