An investigation of the relationship between the liver and brain using an isolated perfused rat brain preparation

The pathogenesis of portal-systemic encephalopathy (PSE) and hepatic encephalopathy (HE), disorders of the brain attributed to abnormal liver function, are poorly understood. This study was conducted to examine if a fundamental, and possibly exclusive, homeostatic interrelationship exists between the liver and brain that might deteriorate during liver failure to result in the syndrome of PSE and HE. An isolated organ perfusion circuit was devised to accommodate an isolated rat brain and an isolated rat liver preparation perfused concomitantly. The survival time of the brain preparation was measured by the maintenance of the spontaneous electroencephalocorticogram and was extended from a median survival time of 35 min (range 22 to 53 min), when perfused alone, to 210 min (range 172 to 480 min), when perfused simultaneously with a liver. Also, concomitant perfusion with an isolated rat liver reduced perfusate glucose concentrations from 200 mg% to a range between 45 to 60 mg%. These data support our hypothesis that a homeostatic interrelationship exists between the liver and brain that is independent of other metabolic influences; disturbance of this relationship may contribute towards the syndrome of PSE and HE.