AJP - Renal Physiology, Vol 258, Issue 6 1528-F1537, Copyright © 1990 by American Physiological Society

ARTICLES

Na(+)-H+ exchange in choroid plexus and CSF in acute metabolic acidosis or alkalosis

V. A. Murphy and C. E. Johanson
Laboratory of Neurosciences, National Institute on Aging, Bethesda, Maryland 20892.

Basolateral Na(+)-H+ exchange was analyzed with an in vivo model of choroid plexus (CP) epithelium in nephrectomized adult rats anesthetized with ketamine. Acid-base balance in blood was altered for 1 h over a pH continuum of 7.19 to 7.53 by equimolar intraperitoneal injections of HCl, NH4Cl, NaCl, or NaHCO3. Compartmental analysis enabled determination of CP intracellular pH (pHi) [dimethadione (DMO) method] and the choroid cellular concentration of 23Na (stable) and 22Na (tracer). HCl acidosis reduced the outwardly directed transmembrane basolateral H+ gradient, lowered the [23Na]i by 25%, and decreased the influx coefficient (Kin) for 22Na from blood into CP parenchyma (by 45% from 0.211 to 0.117 ml.g-1.h-1) and into cerebrospinal fluid (CSF) (by 43%, from 0.897 to 0.516). Compared with acid-loaded rats (HCl or NH4Cl), the NaHCO3-alkalotic animals had significantly enhanced uptake of 22Na into the CP-CSF system. This pH-dependent transport of Na+ from blood to CP was abolished by pretreatment with amiloride, an inhibitor of Na(+)-H+ exchange. Except in severe acidosis (HCl), the choroid cell pHi (7.05 +/- 0.02 in NaCl controls) and [HCO3-] (11-12 mM) remained stable in the face of acidemic and alkalemic challenges. With respect to reaction of the blood-CSF barrier to plasma acid-base perturbations, the responses of the fourth ventricle plexus pHi, [Na+]i, and 22Na uptake were similar to corresponding ones in lateral plexuses. We conclude that in the choroidal epithelium there is a Na(+)-H+ exchange activity capable of modulating Na+ flux into the CSF by approximately 50% as arterial pH is varied from 7.2 to 7.5.

This article has been cited by other articles:

				S. F. Pedersen, M. E. O'Donnell, S. E. Anderson, and P. M. Cala Physiology and pathophysiology of Na+/H+ exchange and Na+-K+-2Cl- cotransport in the heart, brain, and blood Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2006; 291(1): R1 - R25. [Abstract] [Full Text] [PDF]

				J. Praetorius and S. Nielsen Distribution of sodium transporters and aquaporin-1 in the human choroid plexus Am J Physiol Cell Physiol, July 1, 2006; 291(1): C59 - C67. [Abstract] [Full Text] [PDF]

				J. Praetorius, L. N. Nejsum, and S. Nielsen A SCL4A10 gene product maps selectively to the basolateral plasma membrane of choroid plexus epithelial cells Am J Physiol Cell Physiol, March 1, 2004; 286(3): C601 - C610. [Abstract] [Full Text]

				D. Z. Ellis, J. A. Nathanson, and K. J. Sweadner Carbachol inhibits Na+-K+-ATPase activity in choroid plexus via stimulation of the NO/cGMP pathway Am J Physiol Cell Physiol, December 1, 2000; 279(6): C1685 - C1693. [Abstract] [Full Text] [PDF]

				Q. Wu, E. Delpire, S. C. Hebert, and K. Strange Functional demonstration of Na+-K+-2Cl- cotransporter activity in isolated, polarized choroid plexus cells Am J Physiol Cell Physiol, December 1, 1998; 275(6): C1565 - C1572. [Abstract] [Full Text] [PDF]