An instrument and technique for the continuous measurement of respiratory CO 2 patterns in metabolic tracer studies

Abstract

To facilitate metabolic tracer studies with white rats, an instrument has been developed for the continuous analysis and recording of respiratory CO 2. This instrument measures radioactive CO 2 by means of a vibrating reed electrometer, and total CO 2 by means of infrared absorption. Specific activity is recorded separately. A linear integrator makes it possible to read total respired radioactive CO 2 at any point in a metabolic experiment. With this instrument, metabolic data may be obtained by feeding to white rats test materials with C 14 tags at appropriate positions in the molecule, and measuring radioactive and total CO 2 respired. By an indirect approach, metabolic information has been obtained on toxic agents by measuring the effect of these agents on metabolism of a normal nutrient, such as C 14 tagged glucose. The very preliminary results herein reported indicate that ingestion of toxic agents constitutes a biochemical stress with resulting changes in the metabolic pattern of glucose. Parathion and carbon tetrachloride produce significant differences in the metabolic behavior of radio-glucose in white rats subjected to single administrations of sublethal levels of the above agents.