Some aspects of differential labelling of individual mononucleotides derived from nucleic acids of animal cells incorporating [32P] orthophosphate.

Abstract

Specific activities were determined of individual 2′,3′-nucleotides derived from various RNA fractions and 5′-nucleotides derived from DNA and phenol-released RNA in rabbit lymphatic cells and rat liver slices incorporating [32P]orthophosphate for 1–2 hours in vivo or in vitro. The pattern of the specific activity of these nucleotides showed a marked difference between the lymphatic cells and the liver in several respected. In lymphatic cells, 5′-AMP derived from phenol-released RNA had a much lower specific activity than the other 5′-nucleotides, while in the liver 5′AMP showed the highest specific activity among the 5′-nucleotides. In lymphatic cells, the incorporation of radiophosphate into purine 5′-nucleotides of DNA was much lower than that into pyrimidine 5′-nucleotides in vitro, but the experiments in vivo did not result in such an uneven incorporation. Neither phenol-released RNA of lymphatic cells nor DNA of rat liver gave a similar uneven incorporation into purine and pyrimidine 5′-nucleotides in vitro. The incorporation pattern into 2′,3′-nucleotides was somewhat different between total and phenol-released RNA in lymphatic cells. Again no such difference was noted in the liver. A close agreement of the total activity of four 2′,3′-nucleotides of RNa was noted on some occasions, but apparently this was not a general phenomenon. The significance of these findings was discussed briefly.