Get access
Advertisement

Ammonia-induced brain edema and intracranial hypertension in rats after portacaval anastomosis

Authors

  • Andres T. Blei M.D.,

    Corresponding author
    1. Departments of Medicine, Lakeside Veterans Administration Medical and Northwestern University, Chicago, Illinois 60611
    • Lakeside VA Medical Center, Department of Medicine/111E, 333 East Huron Street, Chicago, IL 60611
    Search for more papers by this author
  • Sigurdur Olafsson,

    1. Departments of Medicine, Lakeside Veterans Administration Medical and Northwestern University, Chicago, Illinois 60611
    Search for more papers by this author
  • Guy Therrien,

    1. Neuroscience Research Unit, Andre Viallet Clinical Research Center, Hopital St Luc and Université de Montreal, Montreal, Quebec, Canada H2X 3J4
    Search for more papers by this author
  • Roger F. Butterworth

    1. Neuroscience Research Unit, Andre Viallet Clinical Research Center, Hopital St Luc and Université de Montreal, Montreal, Quebec, Canada H2X 3J4
    Search for more papers by this author

Abstract

Brain edema, leading to intracranial hypertension and brain herniation, is a major cause of death in fulminant liver failure. Astrocyte swelling is a prominent neuropathological feature in experimental fulminant liver failure. It has been postulated that the osmotic effects of glutamine, generated in astrocytes from ammonia and glutamate in a reaction catalyzed by glutamine synthetase, could mediate brain swelling. Normal rats and rats that received a portacaval anastomosis were infused with ammonium acetate or a sodium acetate control; brain water in cerebral cortex was measured with the gravimetry method, intracranial pressure by means of a cisterna magna catheter and cortical amino acids using high-performance liquid chromatography. Although brain edema was detected in both groups receiving ammonia, it was of a greater magnitude in portacaval anastomosis rats (80.94%+0.17% vs. 80.24%+0.09%, p<0.01), resulting in the development of intracranial hypertension. When portacaval anastomosis rats were infused with ammonium acetate and pretreated with 150 mg/kg methionine-sulfoximine, an inhibitor of glutamine synthetase activity, brain edema was ameliorated and intracranial pressure did not rise. A dose-dependent reduction in brain glutamine levels was seen with increasing doses of methionine-sulfoximine; however, brain edema did not decrease beyond the 150 mg/kg dose, suggesting that the increase in brain water was not solely a result of glutamine accumulation. We conclude that brain edema of a magnitude that results in intracranial hypertension is more likely to develop in rats after portacaval anastomosis receiving a continuous ammonia infusion. The osmotic effects of glutamine appear to mediate, but only in part, the increase in brain water seen in this preparation. Other mechanisms in addition to inhibition of glutamine synthesis may mediate the beneficial effects of methionine-sulfoximine seen in this study. (HEPATOLOGY 1994;19:1437–1444.)

Get access to the full text of this article

Ancillary