Studies on the estimation of deoxyribonucleic acid and ribonucleic acid in rat brain

Abstract

A method for the estimation of DNA and RNA in rat brain is described. The principal modifications of preexisting methods involve initial lipid extraction with chloroform-methanol and continuous stirring during alkaline hydrolysis of RNA and acid extraction of DNA. Comparison of ultraviolet-absorptive methods, phosphate determination, and orcinol reaction for RNA, shows a greater degree of correspondence than has previously been reported for brain tissue. Also, a relatively high degre of reproducibility for each of the methods used is obtained with a two-wavelength ultraviolet method. In addition to chemical separation of DNA and RNA components suitable for isotopic studies, an intact lipid fraction is obtained without acid or heating steps.Intracranial injection of [3H]thymidine into young rats resulted in incorporation of as much as 10% of the injected dose into DNA in 2 h.The DNA per cell nucleus obtained from brain homogenates was found to be 6.4[middle dot]10-12 g. On this basis, there 5.5[middle dot]108 cells in the brain of a young adult rat.