Sodium exchange between blood, brain, and CSF in normal and hydrocephalic cats.
The exchange of sodium between blood, brain, and cerebrospinal fluid was studied in normal and kaolin-induced hydrocephalic cats. The ventricles were perfused to measure fluid formation and Na+ exchange rates. 22Na was added to the perfusion fluid or injected intravenously as a tracer for Na+ movement. Na+ and 22Na were also measured in cortical gray and white matter. Na+ relative specific activities were calculated for brain, effluent fluid, and serum. With 22Na in the perfusion fluid, Na+ exchange was not different from nascent Na+ influx for both normal and hydrocephalic cats. Na+ relative specific activities of cortical gray and white matter were 10 times greater in hydrocephalic than in normal cats. This difference in Na+ relative specific activity for brain may be due to a higher diffusion constant or to a lower brain capillary permeability. When 22Na was given intravenously, the Na+ diffusional exchange for normal cats was less than that measured when 22Na+ was in the perfusion fluid. In hydrocephalic cats, the Na+ diffusional exchange was effectively zero. Na+ relative specific activities of cortical gray and white matter were the same for normal and hydrocephalic cats. These findings suggest that the impaired Na+ diffusional exchange may be due to pathological changes in the choroid plexus.
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002415:Cats; D004058:Diffusion; D006849:Hydrocephalus / Q000378:metabolism*; D008954:Models, Biological; D012964:Sodium / Q000097:blood / Q000134:cerebrospinal fluid / Q000378:metabolism*
D012964:Sodium