Regional blood-brain barrier transport of glucose after portacaval anastomosis.

The regional influx of glucose across the blood-brain barrier was measured in rats 5 to 6 weeks after a portacaval anastomosis or sham operation. D-[14C]Glucose was infused intravenously for 15 sec while arterial blood was sampled continuously for measurement of plasma radioactivity and glucose concentration. Brain tissue radioactivity was measured by quantitative autoradiography. Glucose influx and plasma clearance (permeability times surface area; PS) were calculated from the net disintegrations per minute per gram in brain, the plasma radioactivity integral, and the plasma glucose concentration. In shunted rats influx was decreased by about 22% (in the brain as a whole) compared to that in controls. This decrease was almost entirely due to the decrease in plasma glucose concentrations (27%). The PS, normalized to take plasma concentrations into account, showed a slight decrease in most of the brain except the telencephalon. For the brain as a whole this decrease amounted to 11%. The regional PS and glucose utilization are known to be coupled and the relationship between these was the same in sham-operated and shunted rats. The decrease in PS observed in shunted rats was commensurate with their lower rates of glucose use; thus, the transport process of glucose from plasma to brain appeared to be unaffected by portacaval shunting.