Changes in nucleic acids of cells of mouse mammary carcinoma following exposure to X-ray of low dosage

Abstract

1. 1. X-radiation of 150 roentgens caused a continuous decrease in the nucleic acid content of cells of a mouse mammary carcinoma uniformly suspended in Ringer's solution. A dosage of 100 r. produced a variable increase in cellular nucleic acids, which appeared to be correlated with high RNAP DNAP ratios. We believe that this dosage of X-ray caused some increased susceptibility of DNA to alkaline hydrolysis, as shown by the Schmidt-Thannhauser technic (6), resulting in an abnormal increase in RNAP from 30 to 90 minutes after exposure. A dosage of 75 r. produced changes in cellular nucleic acid difficult to interpret. 2. 2. The increase in nucleic acids following X-radiation of 100 r. was interpreted as a synthesis from precursors existing in the cell rather than a recovery from a temporary inhibition in their development. 3. 3. Increase and decrease in RNAP following X-radiation are shown graphically in the accompanying figures in two ways; one, associated with DNAP and taking place up and down along the lines of regression, and the other, not associated with DNAP and occurring in a perpendicular line up and down between lines of regression at points with fixed values of DNAP. In our experiments recorded here, these values of cellular DNAP are 1.00, 1.20 and 1.50 × 10 9− mg.