NaCl absorption in the rabbit ileum. Effect of acid-base variables.
In vivo and in vitro studies suggest that acid-base variables regulate ion transport in the rabbit ileum. The relative importance of these variables on active Na+ and Cl- absorption has not been defined. Isolated, stripped ileal segments were studied under short-circuited conditions in the Ussing flux chamber. Unidirectional 22Na and 36Cl fluxes were measured after changes in bathing solution pH, PCO2, and/or [HCO3-]. When pH was decreased from 7.6 to 7.1, net flux of Na+ increased from 0.1 +/- 0.7 to 2.6 +/- 0.7 mu Eq/cm2 per hour and net flux of Cl- increased from -2.0 +/- 0.9 to 1.3 +/- 0.6 mu Eq/cm2 per hour. These changes were rapid in onset, completely reversible, and accounted for by changes in mucosal-to-serosal fluxes of these ions. They were accompanied by small decreases in short-circuit current, but there were no changes in residual flux. These pH effects were not inhibited by the presence of luminal bumetanide (1 mmol/L), furosemide (1 mmol/L), hydroflumethiazide (1 mmol/L), or 4,4'-diisothiocyanostilbene-2,2'-disulfonate (1 mmol/L), or by the carbonic anhydrase inhibitor methazolamide (1 mmol/L). When data from all combinations of acid-base conditions were combined and analyzed by linear regression, pH was the only variable that correlated with mucosal-to-serosal fluxes (r = -0.84) and net flux (r = -0.85) for Na+, mucosal-to-serosal fluxes (r = -0.96) and net flux (r = -0.99) for Cl-, and short-circuit current (r = 0.97). These findings suggest that extracellular pH modulates active Na+ and Cl- absorption in the rabbit ileum.
Charney
A N
AN
Nephrology Section, Department of Veterans Affairs Medical Center, New York, New York.
Egnor
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RW
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates; D001692:Biological Transport; D002034:Bumetanide / Q000494:pharmacology; D002245:Carbon Dioxide; D005665:Furosemide / Q000494:pharmacology; D006857:Hydroflumethiazide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007082:Ileum / Q000378:metabolism*; D066298:In Vitro Techniques; D007408:Intestinal Absorption; D007552:Isotonic Solutions; D008297:Male; D008704:Methazolamide / Q000494:pharmacology; D011817:Rabbits; D000077331:Ringer's Solution; D012965:Sodium Chloride / Q000493:pharmacokinetics*
D001639:Bicarbonates; D007552:Isotonic Solutions; D002034:Bumetanide; D002245:Carbon Dioxide; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D012965:Sodium Chloride; D006857:Hydroflumethiazide; D005665:Furosemide; D000077331:Ringer's Solution; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D008704:Methazolamide