The In Vivo Use of Doubly-Labeled Glucose to Determine Cerebral Metabolism in Humans
An arterio-venous method was developed in this laboratory a number of years ago for the determination of cerebral metabolism in humans in vivo [1,2]. It consists briefly of giving the subject an intravenous injection of a labeled substrate and then drawing simultaneous arterial (femoral) and venous (internal-jugular bulb) blood samples at various time intervals. These blood samples are analyzed for radioactivity of the injected substrate, of the end product of metabolism of the substrate (carbon dioxide and/or water) and of intermediate metabolites (i.e., lactate and pyruvate). The increase in radioactivity of the end product in venous blood over its radioactivity in arterial blood is considered as due to catabolism of the substrate by the brain.
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