Glucose consumption decreases throughout the brain only hours after portacaval shunting.

The cerebral metabolic rate for glucose (CMRGlc) was measured at the level of individual structures 6, 12, 24, and 48 h and 4 wk after the formation of a portacaval shunt in rats, a model of hepatic encephalopathy. A quantitative autoradiographic technique with [6-14C]glucose as tracer was used. After 6 h, CMRGlc was depressed in all areas measured by an average of 16%. By 48 h, CMRGlc fell further and reached a value comparable to that seen in rats shunted for many weeks (25-30% below normal). The decrease in CMRGlc occurred throughout the brain to about the same degree. CMRGlc was also measured with another tracer, deoxy-D-[14C]glucose, 48 h after portacaval shunting. The deoxy-D-glucose results agreed with those obtained with [6-14C]glucose. The decrease in CMRGlc may be interpreted to be a consequence of the decreased activity of brain cells, reflecting the cerebral dysfunction that occurs when liver function is inadequate. The experiments demonstrate that the onset of cerebral dysfunction occurs within hours of portacaval shunting and is fully established within days.