Na+,K(+)-ATPase activities are increased in brain in both congenital and acquired hyperammonemic syndromes.

Activities of Na+,K(+)-ATPase were measured in brain regions of experimental animals with either congenital or acquired hyperammonemia. In the sparse-fur (spf) mutant mouse, with a genetic X-linked deficiency of ornithine transcarbamylase, an animal model of congenital hyperammonemia, Na+,K(+)-ATPase was increased in frontal cortex (by 57%, P < 0.001), cerebellum (by 61%, P < 0.001), brainstem (by 71%, P < 0.001) and striatum (by 48%, P < 0.01). Four weeks following portacaval anastomosis in the rat, Na+,K(+)-ATPase activities were increased in cerebellum and striatum (by 19%, P < 0.01) and in brainstem (by 28%, P < 0.01). Stimulation of Na+,K(+)-ATPase and the subsequent alteration of neuronal excitability could contribute to the CNS dysfunction characteristic of chronic hyperammonemic syndromes.