Active transport of chloride by lateral ventricle choroid plexus of the rat.
The nature of Cl transport and its relation to Na and K transport were analyzed in adult rat lateral ventricle choroid plexus incubated in cerebrospinal fluid (CSF) medium at 37 degrees C and PCO2 = 30 mmHg. In synthetic CSF (extracellular Cl [( Cl]o) = 130 mM), the intracellular Cl [( Cl]i) was three times that estimated for passive distribution. Choroid plexus [Cl]i was not determined by Donnan distribution because [Cl]i remained constant at approximately 50 mM while the [K]i/[K]o ratio was varied 10-fold by drugs and cation substitutions. A [Cl]i/[Cl]o ratio of approximately 0.38 was found when [Cl]o was varied from 15 to 130 mM by isosmotic replacement of Cl with methyl sulfate or isethionate. However, the [Cl]i/[Cl]o ratio increased to greater than 1.0 when [Cl]o was lowered below 5 mM. Reduction in bath temperature to 15 degrees C (CSF PCO2 = 50 mmHg) increased both [Cl]i/[Cl]o and [HCO3]i/[HCO3]o to approximately 0.6. SITS, an inhibitor of Cl-HCO3 transport, reduced [Cl]i by 18 mM, decreasing the [Cl]i/[Cl]o ratio close to the equilibrium value. In contrast, neither furosemide (10(-3) M) nor low CSF [Na]o (3 mM) reduced Cl accumulation. It is concluded that uphill movement of Cl into choroid plexus epithelium occurs primarily by Cl-HCO3 antiport and not by Na-Cl symport.
Smith
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D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D018723:Bethanechol; D001626:Bethanechol Compounds / Q000494:pharmacology; D001693:Biological Transport, Active; D002552:Cerebral Ventricles / Q000378:metabolism; D002555:Cerebrospinal Fluid / Q000502:physiology; D002712:Chlorides / Q000378:metabolism*; D002831:Choroid Plexus / Q000187:drug effects / Q000378:metabolism*; D004140:Dinitrophenols / Q000494:pharmacology; D004976:Ethacrynic Acid / Q000494:pharmacology; D005665:Furosemide / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D013696:Temperature
D001626:Bethanechol Compounds; D002712:Chlorides; D004140:Dinitrophenols; D007473:Ion Channels; D018723:Bethanechol; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D010042:Ouabain; D005665:Furosemide; D012964:Sodium; D007545:Isoproterenol; D004976:Ethacrynic Acid; D000086:Acetazolamide; D011188:Potassium; D009638:Norepinephrine