NUCLEIC ACID CONTENT OF RETICULOCYTES AND ITS RELATION TO UPTAKE OF RADIOACTIVE LEUCINE IN VITRO

Abstract

Over the last two decades much evidence of an indirect nature has suggested that nucleic acids may be controlling factors in protein synthesis. A number of workers, notably Caspersson and Schultz (1, 2), Brachet (3), and Thorell (4), have shown that high concentrations of ribose nucleic acid are found in embryonic and neoplastic tissues. Although in many cases no direct measurements were made on the amount of protein synthesis, it was reasonably assumed that the types of tissues used were actively synthesizing protein. Spiegelman and Kamen (5) have raised the objection as to whether the correlation between the amount of ribose nucleic acid and protein synthesis was of any real value in determining the effect of nucleic acids on protein synthesis. They pointed out that equally good correlations can be obtained between protein synthesis and other phosphate fractions. Thorell (4), using bone marrow tissue, claimed evidence for the existence of different phases during the formation of protein in red blood cells, with correlated changes in the ribose nucleic acid. It has been shown by Borsook et al. (6) that reticulocytes, but not erythrocytes, rapidly incorporate radioactive amino acids. This suggested the possibility of measuring simultaneously both amino acid incorporation and nucleic acid content in a system in which both could be expected to be undergoing rapid change.