The brain in experimental portal-systemic encephalopathy. II. Water and electrolyte changes.

The water content and amounts of sodium, potassium and chloride were measured in the brains of normal rats, rats with PCA, normal rats fed ammoniated cationic exchange resin, and rats with PCA fed the resin. Plasma electrolytes and ammonia levels were also measured, and sodium and chloride spaces were calculated. Rats with PCA showed increased water content, sodium space and chloride space in the brainstem compared to controls. Rats with PCA fed ammoniated resin showed increased chloride content and Na+:K+ ratio in the brainstem, and an increased chloride space in the brainstem. In these rats the chloride spaces in the cerebrum and cerebellum exceeded the sodium spaces. It is concluded that high circulating ammonia levels can in vivo produce ionic shifts which may interfere with nervous function. It is also concluded that increased cytoplasmic osmolarity produced by ammonium ion-induced stimulation of (Na+ + Ka+) ATPase may result in the appearance of swollen astrocytes in conventional electron micrographs.