An animal model of inappropriate antidiuretic hormone secretion was used to study changes in water and electrolytes in water intoxication. As the serum became hypotonic, brain and muscle initially reacted by swelling and decreasing sodium content. Subsequently, muscle continued to swell and maintained normal potassium levels. Brain decreased its dry weight potassium content by 20% and swelled half as much as muscle. The critical factor in determination of consciousness was the level of brain water, not the level of sodium or potassium. Grey and white matter were affected equally. Permeability to mannitol was normal in the experimental model. Corticosteroids were found to have no effect on the syndrome. The drop in brain potassium level is interpreted as a protective adaptation to prevent massive swelling as occurred in muscle.
Rymer MM, Fishman RA. Protective Adaptation of Brain to Water Intoxication. Arch Neurol. 1973;28(1):49–54. doi:10.1001/archneur.1973.00490190067009
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