AJP - Renal Physiology, Vol 249, Issue 4 470-F477, Copyright © 1985 by American Physiological Society
Active transport of chloride by lateral ventricle choroid plexus of the rat
Q. R. Smith and C. E. Johanson
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.
