Active transport of sodium and potassium by the choroid plexus of the rat.
1. Choroid plexus from the lateral ventricle in the adult rat was found to contain approximately 54 m-equiv Na(+) and 89 m-equiv K(+) per kg wet tissue.2. The total water (79%), the extracellular space (21%) and the red blood cell volume (8-9%) in choroid plexus were quantified separately by analysing the distribution of [(14)C]antipyrine, [(14)C]inulin and (51)Cr-tagged erythrocytes, respectively, between this tissue and plasma water.3. The tissue electrolyte data together with the compartmental (space) data were used to calculate an average concentration of Na(+) (39 m-equiv/kg cell H(2)O) and of K(+) (144) in the choroid cell.4. Under various experimental conditions known to stimulate or inhibit the Na(+)-K(+) transport system in other tissues, there were significant changes (10-40 m-equiv/kg cell H(2)O) in the concentrations of both these cations in the plexus epithelial cells.5. Choroid cell K(+) was not independent of the concentration of K(+) in plasma since substantial fluctuations in cell K(+) occurred in rats rendered either hypo- or hyperkalaemic; also, the choroid cell apparently cannot maintain a constant gradient between itself and c.s.f. in the face of kalaemic disturbances.6. Evidence is offered to support the hypothesis that the choroid plexus of the lateral ventricle has a Na(+)-K(+) pump, the operation of which contributes to the maintenance of K(+) homoeostasis in the C.N.S.
D000818:Animals; D000983:Antipyrine / Q000378:metabolism; D001693:Biological Transport, Active; D001834:Body Water / Q000378:metabolism; D001923:Brain Chemistry; D002540:Cerebral Cortex / Q000378:metabolism; D002552:Cerebral Ventricles / Q000378:metabolism; D002831:Choroid Plexus / Q000378:metabolism*; D003900:Desoxycorticosterone / Q000031:analogs & derivatives / Q000494:pharmacology; D004032:Diet; D005110:Extracellular Space / Q000378:metabolism; D006947:Hyperkalemia / Q000378:metabolism; D007008:Hypokalemia / Q000378:metabolism; D007444:Inulin / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000032:analysis; D009392:Nephrectomy; D011188:Potassium / Q000134:cerebrospinal fluid / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000134:cerebrospinal fluid / Q000378:metabolism*
D003900:Desoxycorticosterone; D007444:Inulin; D012964:Sodium; D011188:Potassium; D000983:Antipyrine