THE ROLE OF pH GRADIENT IN THE DISTRIBUTION OF AMMONIA BETWEEN BLOOD AND CEREBROSPINAL FLUID, BRAIN AND MUSCLE*

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Abstract
Simultaneous brain, muscle, and cerebrospinal fluid (CSF) ammonia concentrations were serially determined in 51 nephrectomized dogs during constant intravenous infusion of 0.16 N NH4HCO3 and were related to arterial whole blood ammonia concentrations at corresponding times. Temporary pH gradients between blood and CSF, brain and muscle were induced by means of intravenous infusion of 0.2 N HCL and 0.2 N NaOH solution or elevation and depression of pCO2 through respiratory means. A direct and predictable relation was observed between the diffusion of ammonia into CSF and the magnitude and direction of a gradient in pH between blood and CSF. The ratio of concentration of ammonia in CSF to that in blood was increased as the pH of blood exceeded the pH of CSF, while the ratio was decreased as the pH of blood approximated or was less than the pH of CSF. Similarly tissue ammonia concentration increased during metabolic and respiratory alkalosis and decreased during metabolic and respiratory acidosis.