Sodium, chloride, and bicarbonate movement from plasma to cerebrospinal fluid in cats

Rate constants have been determined for the entry of 22Na+, 36Cl minus, and H14CO3- into CSF from plasma in cats during changes in Pco2 with and without inhibition of carbonic anhydrase. The application of these rate constants to movement of unlabeled electrolytes suggests that Na+ and Cl minus ente...

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Bibliographic Details
Published in:	The American journal of physiology Vol. 228; no. 3; pp. 673 - 683
Main Authors:	Vogh, B.P, Maren, T.H
Format:	Journal Article
Language:	English
Published:	United States 01-03-1975
Subjects:	Acetazolamide - pharmacology Acid-Base Equilibrium animal science Animals Bicarbonates - blood Bicarbonates - cerebrospinal fluid Bicarbonates - metabolism Biological Transport Blood-Brain Barrier Carbon Dioxide - blood Carbonic Anhydrase Inhibitors Cats Chlorides - blood Chlorides - cerebrospinal fluid Chlorides - metabolism livestock Methazolamide - pharmacology Models, Biological Partial Pressure Sodium - blood Sodium - cerebrospinal fluid Sodium - metabolism zoology
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Summary:	Rate constants have been determined for the entry of 22Na+, 36Cl minus, and H14CO3- into CSF from plasma in cats during changes in Pco2 with and without inhibition of carbonic anhydrase. The application of these rate constants to movement of unlabeled electrolytes suggests that Na+ and Cl minus enter CSF by a one-way flux into newly formed fluid, but that entering HCO3-is involved both in net accumulation in new fluid and in rapid exchange with existing HCO3-. The entering HCO3-ions are not transferred from plasma but are formed in secretory cells from dissolved CO2. The exchange component of HCO3-entry is Pco2-dependent; entry of Na+ and Cl minus is not; hence net rate of HCO3-formation estimated by difference between Na+ and Cl minus is not Pco2 dependent. The net rate of HCO3-formation lies within the availability of CO2 from blood flow to choroid plexus but is not necessarily limited to this tissue. When carbonic anhydrase is inhibited, the net rate of formation of HCO3-is close to the calculated uncatalyzed rate expected for choroid plexus. The entry of all three ions is reduced by carbonic anhydrase inhibition, but the enzyme does not seem to provide the primary signal for alteration of CSF acid-base status. Regulation of CSF pH appears to be achieved through changes in HCO3-concentration that occur subsequent to the secretion of HCO3--rich new fluid.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0002-9513 2163-5773
DOI:	10.1152/ajplegacy.1975.228.3.673