CEREBRAL GLUCOSE-TRANSPORT AND METABOLISM IN PRETERM HUMAN INFANTS

Few data regarding early developmental changes in cerebral (blood-to-b rain) glucose transport (CTXglc) and CMRglc are available for humans. We measured CBF, CTXglc, and CMRglc with positron emission tomography at 4 to 7 days of life in six preterm human infants whose estimated ge stational age was 25 to 34 weeks. The Michaelis-Menten constants K-t a nd T-max were estimated from CTXglc and the calculated cerebral capill ary plasma glucose concentration. Mean CMRglc was 8.8 mu mol 100 g(-1) min(-1). The CMRglc did not correlate with plasma glucose concentrati on (r = .315, P = .543), whereas CTXglc showed a significant correlati on with plasma glucose concentration (r = .836, P = .038). Estimation of the Michaelis-Menten constants from the best fit to the measured da ta produced values of K-t = 6.0 mu mol mL(-1) and T-max = 32.6 mu mol 100 g(-1) min(-1). These values for K-t in the developing human brain are similar to those that have been reported for the mature brain of a dolescent and adult humans and adult nonhuman primates, indicating the affinity of the glucose transport protein for D-glucose is similar. H owever, T-max is approximately one third to one half of the comparable values for mature brain, indicating a reduced number of available lum inal transporters.