Cerebral blood flow and metabolism in chronically hyperammonemic rats: effect of an acute ammonia challenge.

A. Gjedde, A. H. Lockwood, T. E. Duffy, F. Plum

Research output: Contribution to journalArticle

Abstract

The effects of chronic hyperammonemia on cerebral metabolism were studied in rats four and eight weeks after the construction of a portacaval shunt. Compared to sham-operated controls, shunted animals had increased arterial concentrations of ammonia and glutamine and decreased glutamate. Cerebral blood flow, measured by xenon 133 washout in animals lightly anesthetized with nitrous oxide, increased from a control of 91 +/- 5 (mean +/- SEM) to 139 +/- 20 ml per 100 gm tissue per minute after shunting for eight weeks; however, the cerebral metabolic rate for oxygen was not different from control four or eight weeks after the shunting procedure. Following intraperitoneal administration of a small ammonium acetate load (2.6 mmol/kg), eight-week portacaval animals consistently underwent a fall in cerebral blood flow and cerebral oxygen consumption and developed high-voltage slow waves in the electroencephalogram. Glutamine was produced by the brains of all groups of animals; the cerebral metabolic rate for glutamine was greater than control in eight-week portacaval rats, the only animals to show a net uptake of ammonia into brain. The findings suggest that increased cerebral sensitivity to ammonia, along with nonspecific effects of chronic portal-systemic shunting, may lead to uncoupling of cerebral blood flow and oxidative metabolism.

Original languageEnglish (US)
Pages (from-to)325-330
Number of pages6
JournalAnnals of Neurology
Volume3
Issue number4
Publication statusPublished - Apr 1978
Externally publishedYes

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ASJC Scopus subject areas

  • Neuroscience(all)

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