Volume expansion-induced alterations in proximal tubule chloride gradient in the rat.
To elucidate the mechanisms by which acute volume expansion (AVE) induces a decrease in proximal tubule transepithelial chloride gradient, male Sprague-Dawley rats were studied before and after AVE with Ringer lactate. In group 1, after AVE equivalent to 10% body wt, there were decreases in both tubule fluid to plasma inulin ratio ((TF/P)In) (from 2.28 +/- 0.10 to 1.57 +/- 0.05) and tubule fluid to ultrafiltrate chloride ratio ((TF/UF)Cl) (from 1.25 +/- 0.02 to 1.18 +/- 0.02). Group 2 was studied during carbonic anhydrase inhibition (CAI) produced by benzolamide before and during superimposed AVE (20% body wr). Both (TF/P)In (from 1.91 +/- 0.10 to 1.41 +/- 0.08) and (TF/UF)Cl (from 1.07 +/- 0.02 to 1.01 +/- 0.01) decreased. Group 3 was studied during maintained AVE (15% body wt) as a control for group 4, in which CAI was superimposed on maintained AVE. In group 3, (TF/P)In and (TF/UF)Cl did not change, but in group 4 CAI was associated with a decrease in (TF/P)In (from 1.55 +/- 0.05 to 1.21 +/- 0.05) and in (TF/UF)Cl (from 1.16 +/- 0.01 to 1.04 +/- 0.07). These data suggest that in the superficial proximal convoluted tubule of the rat, AVE-induced alterations in transepithelial chloride gradient are dependent on a mechanism(s) other than changes in carbonic anhydrase-mediated bicarbonate reabsorption.
D000818:Animals; D001574:Benzolamide / Q000494:pharmacology; D002257:Carbonic Anhydrase Inhibitors; D002712:Chlorides / Q000378:metabolism* / Q000652:urine; D005110:Extracellular Space / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D051381:Rats; D012964:Sodium / Q000652:urine
D002257:Carbonic Anhydrase Inhibitors; D002712:Chlorides; D012964:Sodium; D001574:Benzolamide