Nomogram for 2-deoxyglucose lumped constant for rat brain cortex.

The quantitation of local cerebral metabolic rate of glucose with the 2-deoxyglucose technique of Sokoloff requires the use of a correction factor, or lumped constant. We have shown previously (Pardridge et al., 1982) that a simple model may be formulated to predict changes in the lumped constant that occur due to alterations in the distribution of glucose and 2-deoxyglucose in brain. Given experimentally observed values for brain and plasma glucose concentrations, the 2-deoxyglucose lumped constant may be determined from a nomogram constructed from knowledge of the blood-brain barrier transport constants (KM, Vmax, KD) for glucose and for 2-deoxyglucose. However, the nomogram is constructed from transport constants determined in the barbiturate-anesthetized state. The applicability of the nomogram to other physiologic states was examined in the present studies. Large changes in blood-brain barrier hexose transport constants do not appreciably alter the shape of the nomogram, if the changes in KM or Vmax for glucose or for 2-deoxyglucose are the same. Moreover, glucose and 2-deoxyglucose are both transported by the same hexose carrier, and selective changes in the transport of only one hexose have not been reported. Therefore, it is probable that the nomogram constructed from transport constants measured under barbiturate anesthesia is useful in predicting the lumped constant in a variety of physiologic states.