CONSTANCY OF DNA CONTENT IN ADRENAL MEDULLA NUCLEI OF COLD-TREATED RATS

Abstract

Reports of changes in DNA content of certain typss of cells following exposure to conditions of stress has led to the suggestion that two kinds of DNA may be present. One is genetic DNA, and the other is called metabolic DNA. In a further attempt to investigate the possibility of this phenomenon, determinations of DNA content were made on Feulgen-stained nuclei of adrenal glands and kidneys in cold-treated rats. Feulgen-stained nuclei were measured by two-wavelength micro-spectrophotometry. Particular attention was given to the handling of the smears in hydrolysis and staining. Mean values of Feulgen-DNA contents in a total of 720 muclei demonstrated: a constancy of DNA content with 2 percent in individual nuclei both in adrenal medulla and kidney cortex; no more than an average of 2 percent difference in DNA content between control and experimental nuclei; and no more than an average of 1. 5 percent difference in DNA content between normal kidney cortex nuclei and normal adrenal medulla nuclei. These results confirm the view that the more precise the measurement, the more accurately the constancy rule is obeyed. Moreover, there is no support for the concept of a metabolic DNA in the rat adrenal medulla.