In vivo measurement of brain glucose transport and metabolism employing glucose- -11C.

The radiopharmaceutical glucose--11C was used in vivo measurement of brain-glucose transport kinetics and metabolism in the rhesus monkey. Radiotracer was injected intravenously as a bolus. Radioactivity was continuously recorded from the head and from the arterial blood via an indwelling peripheral artery catheter for a collectionperiod of 2-3 min. To correct the reading obtained from the head for radioactivitycontained in blood, a second intravenous injection of the vascular tracer -15O-labeled carboxyhemoglobin was used. The method was tested in nine phencyclidine-anesthetized monkeys in which cerebral glucose metabolism (CMRGlc) was simultaneously measured by our method and by a standard method emplying the Fick principle. A highlysignificant correlation was found between the two methods of measuring CMRGlc (r =0.929). In addition, our model predicted a ratio of forward-to-reverse glucose flux across the blood-brain barrier (BBR) (1.37 plus or minus 0.23 SD), the brain-to-bloodglucose concentration ratio across the BBB (0.633 plus or minus 0.14), the relative tissue free-glucose space (17 plus or minus 7%), the brain free-glucose concentration (13.6plus or minus 8.5 mg/100 g of tissue), and the brain free-glucose turnover time (2.96 plus or minus 1.98 min). author