Skip to main content
NCBI home page
The Journal of Clinical Investigation logoLink to The Journal of Clinical Investigation
. 1984 Apr;73(4):1034–1045. doi: 10.1172/JCI111288

Internephron heterogeneity for carbonic anhydrase-independent bicarbonate reabsorption in the rat.

J P Frommer, M E Laski, D E Wesson, N A Kurtzman
PMCID: PMC425116  PMID: 6423664

Abstract

The present experiments were designed to localize the sites of carbonic anhydrase-independent bicarbonate reabsorption in the rat kidney and to examine some of its mechanisms. Young Munich-Wistar rats were studied using standard cortical and papillary free-flow micropuncture techniques. Total CO2 (tCO2) was determined using microcalorimetry. In control rats both superficial and juxtamedullary proximal nephrons reabsorbed approximately 95% of the filtered load of bicarbonate. The administration of acetazolamide (20 mg/kg body weight [bw]/h) decreased proximal reabsorption to 65.6% of the filtered load in superficial nephrons (32% was reabsorbed by the proximal convoluted tubule while 31.7% was reabsorbed by the loop segment), and to 38.4% in juxtamedullary nephrons. Absolute reabsorption of bicarbonate was also significantly higher in superficial than in juxtamedullary nephrons after administration of acetazolamide (727 +/- 82 vs. 346 +/- 126 pmol/min; P less than 0.05). The infusion of amiloride (2.5 mg/kg bw/h) to acetazolamide-treated rats increased the fractional excretion of bicarbonate as compared with animals treated with acetazolamide alone (34.9 +/- 1.9 vs. 42.9 +/- 2.1%; P less than 0.01), and induced net addition of bicarbonate between the superficial early distal tubule and the final urine (34.8 +/- 3.0 vs. 42.9 +/- 2.1%; P less than 0.05). Amiloride at this dose did not affect proximal water or bicarbonate transport; our studies localize its site of action to the terminal nephron. Vasa recta (VR) plasma and loop of Henle (LH) tubular fluid tCO2 were determined in control and acetazolamide-treated rats in order to identify possible driving forces for carbonic anhydrase-independent bicarbonate reabsorption in the rat papilla. Control animals showed a tCO2 gradient favoring secretion (LH tCO2, 7.4 +/- 1.7 mM vs. VR tCO2, 19.1 +/- 2.3 mM; P less than 0.005). Acetazolamide administration reversed this chemical concentration gradient, inducing a driving force favoring reabsorption of bicarbonate (LH tCO2, 27.0 +/- 1.4 mM vs. VR tCO2, 20.4 +/- 1.0 mM; P less than 0.005). Our study shows that in addition to the superficial proximal convoluted tubule, the loop segment and the collecting duct show acetazolamide-insensitive bicarbonate reabsorption. No internephron heterogeneity for bicarbonate transport was found in controls. The infusion of acetazolamide, however, induced significant internephron heterogeneity for bicarbonate reabsorption, with superficial nephrons reabsorbing a higher fractional and absolute load of bicarbonate than juxtamedullary nephrons. We think that the net addition of bicarbonate induced by amiloride is secondary to inhibition of voltage-dependent, carbonic anhydrase-independent bicarbonate reabsorption at the level of the collecting duct, which uncovers a greater delivery of carbonate from deeper nephrons to the collecting duct. Finally, our results suggest that carbonic anhydrase-independent bicarbonate reabsorption is partly passive, driven by favorable chemical gradients in the papillary tubular structures, and partly voltage-dependent, in the collecting duct.

Full text

PDF
1034

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Arruda J. A., Subbarayudu K., Dytko G., Mola R., Kurtzman N. A. Voltage-dependent distal acidification defect induced by amiloride. J Lab Clin Med. 1980 Mar;95(3):407–416. [PubMed] [Google Scholar]
  2. Berry C. A. Heterogeneity of tubular transport processes in the nephron. Annu Rev Physiol. 1982;44:181–201. doi: 10.1146/annurev.ph.44.030182.001145. [DOI] [PubMed] [Google Scholar]
  3. Burg M., Green N. Bicarbonate transport by isolated perfused rabbit proximal convoluted tubules. Am J Physiol. 1977 Oct;233(4):F307–F314. doi: 10.1152/ajprenal.1977.233.4.F307. [DOI] [PubMed] [Google Scholar]
  4. Chan Y. L., Biagi B., Giebisch G. Control mechanisms of bicarbonate transport across the rat proximal convoluted tubule. Am J Physiol. 1982 May;242(5):F532–F543. doi: 10.1152/ajprenal.1982.242.5.F532. [DOI] [PubMed] [Google Scholar]
  5. Chan Y. L., Giebisch G. Relationship between sodium and bicarbonate transport in the rat proximal convoluted tubule. Am J Physiol. 1981 Mar;240(3):F222–F230. doi: 10.1152/ajprenal.1981.240.3.F222. [DOI] [PubMed] [Google Scholar]
  6. Cogan M. G., Maddox D. A., Warnock D. G., Lin E. T., Rector F. C., Jr Effect of acetazolamide on bicarbonate reabsorption in the proximal tubule of the rat. Am J Physiol. 1979 Dec;237(6):F447–F454. doi: 10.1152/ajprenal.1979.237.6.F447. [DOI] [PubMed] [Google Scholar]
  7. DuBose T. D., Jr, Lucci M. S. Effect of carbonic anhydrase inhibition on superficial and deep nephron bicarbonate reabsorption in the rat. J Clin Invest. 1983 Jan;71(1):55–65. doi: 10.1172/JCI110751. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. DuBose T. D., Jr, Pucacco L. R., Lucci M. S., Carter N. W. Micropuncture determination of pH, PCO2, and total CO2 concentration in accessible structures of the rat renal cortex. J Clin Invest. 1979 Aug;64(2):476–482. doi: 10.1172/JCI109485. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. DuBose T. D., Jr, Pucacco L. R., Seldin D. W., Carter N. W., Kokko J. P. Microelectrode determination of pH and PCO2 in rat proximal tubule after benzolamide: evidence for hydrogen ion secretion. Kidney Int. 1979 Jun;15(6):624–629. doi: 10.1038/ki.1979.82. [DOI] [PubMed] [Google Scholar]
  10. Friedman P. A., Andreoli T. E. CO2-stimulated NaCl absorption in the mouse renal cortical thick ascending limb of Henle. Evidence for synchronous Na +/H+ and Cl-/HCO3- exchange in apical plasma membranes. J Gen Physiol. 1982 Nov;80(5):683–711. doi: 10.1085/jgp.80.5.683. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Hulter H. N., Ilnicki L. P., Licht J. H., Sebastian A. On the mechanism of diminished urinary carbon dioxide tension caused by amiloride. Kidney Int. 1982 Jan;21(1):8–13. doi: 10.1038/ki.1982.2. [DOI] [PubMed] [Google Scholar]
  12. Imai M. Function of the thin ascending limb of Henle of rats and hamsters perfused in vitro. Am J Physiol. 1977 Mar;232(3):F201–F209. doi: 10.1152/ajprenal.1977.232.3.F201. [DOI] [PubMed] [Google Scholar]
  13. Jacobson H. R. Effects of CO2 and acetazolamide on bicarbonate and fluid transport in rabbit proximal tubules. Am J Physiol. 1981 Jan;240(1):F54–F62. doi: 10.1152/ajprenal.1981.240.1.F54. [DOI] [PubMed] [Google Scholar]
  14. Johnston P. A., Battilana C. A., Lacy F. B., Jamison R. L. Evidence for a concentration gradient favoring outward movement of sodium from the thin loop of Henle. J Clin Invest. 1977 Feb;59(2):234–240. doi: 10.1172/JCI108633. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Kinsella J. L., Aronson P. S. Amiloride inhibition of the Na+-H+ exchanger in renal microvillus membrane vesicles. Am J Physiol. 1981 Oct;241(4):F374–F379. doi: 10.1152/ajprenal.1981.241.4.F374. [DOI] [PubMed] [Google Scholar]
  16. Koeppen B. M., Helman S. I. Acidification of luminal fluid by the rabbit cortical collecting tubule perfused in vitro. Am J Physiol. 1982 May;242(5):F521–F531. doi: 10.1152/ajprenal.1982.242.5.F521. [DOI] [PubMed] [Google Scholar]
  17. Kokko J. P. Sodium chloride and water transport in the descending limb of Henle. J Clin Invest. 1970 Oct;49(10):1838–1846. doi: 10.1172/JCI106401. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Kunau R. T., Jr The influence of the carbonic anhydrase inhibitor, benzolamide (CL-11,366), on the reabsorption of chloride, sodium, and bicarbonate in the proximal tubule of the rat. J Clin Invest. 1972 Feb;51(2):294–306. doi: 10.1172/JCI106814. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Laski M. E., Kurtzman N. A. Characterization of acidification in the cortical and medullary collecting tubule of the rabbit. J Clin Invest. 1983 Dec;72(6):2050–2059. doi: 10.1172/JCI111170. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Laski M. E., Warnock D. G., Rector F. C., Jr Effects of chloride gradients on total CO2 flux in the rabbit cortical collecting tubule. Am J Physiol. 1983 Feb;244(2):F112–F121. doi: 10.1152/ajprenal.1983.244.2.F112. [DOI] [PubMed] [Google Scholar]
  21. Levine D. Z., Byers M. K., McLeod R. A., Luisello J. A., Raman S. Loop of Henle bicarbonate accumulation in vivo in the rat. J Clin Invest. 1979 Jan;63(1):59–66. doi: 10.1172/JCI109278. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Lombard W. E., Kokko J. P., Jacobson H. R. Bicarbonate transport in cortical and outer medullary collecting tubules. Am J Physiol. 1983 Mar;244(3):F289–F296. doi: 10.1152/ajprenal.1983.244.3.F289. [DOI] [PubMed] [Google Scholar]
  23. Lucci M. S., Pucacco L. R., Carter N. W., DuBose T. D., Jr Evaluation of bicarbonate transport in rat distal tubule: effects of acid-base status. Am J Physiol. 1982 Oct;243(4):F335–F341. doi: 10.1152/ajprenal.1982.243.4.F335. [DOI] [PubMed] [Google Scholar]
  24. Lucci M. S., Warnock D. G., Rector F. C., Jr Carbonic anhydrase-dependent bicarbonate reabsorption in the rat proximal tubule. Am J Physiol. 1979 Jan;236(1):F58–F65. doi: 10.1152/ajprenal.1979.236.1.F58. [DOI] [PubMed] [Google Scholar]
  25. Maren T. H. Chemistry of the renal reabsorption of bicarbonate. Can J Physiol Pharmacol. 1974 Dec;52(6):1041–1050. doi: 10.1139/y74-138. [DOI] [PubMed] [Google Scholar]
  26. Maren T. H. Use of inhibitors in physiological studies of carbonic anhydrase. Am J Physiol. 1977 Apr;232(4):F291–F297. doi: 10.1152/ajprenal.1977.232.4.F291. [DOI] [PubMed] [Google Scholar]
  27. McKinney T. D., Burg M. B. Bicarbonate absorption by rabbit cortical collecting tubules in vitro. Am J Physiol. 1978 Feb;234(2):F141–F145. doi: 10.1152/ajprenal.1978.234.2.F141. [DOI] [PubMed] [Google Scholar]
  28. McKinney T. D., Burg M. B. Biocarbonate and fluid absorption by renal proximal straight tubules. Kidney Int. 1977 Jul;12(1):1–8. doi: 10.1038/ki.1977.72. [DOI] [PubMed] [Google Scholar]
  29. Richardson R. M., Kunau R. T., Jr Bicarbonate reabsorption in the papillary collecting duct: effect of acetazolamide. Am J Physiol. 1982 Jul;243(1):F74–F80. doi: 10.1152/ajprenal.1982.243.1.F74. [DOI] [PubMed] [Google Scholar]
  30. Rocha A. S., Kokko J. P. Sodium chloride and water transport in the medullary thick ascending limb of Henle. Evidence for active chloride transport. J Clin Invest. 1973 Mar;52(3):612–623. doi: 10.1172/JCI107223. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Rosin J. M., Katz M. A., Rector F. C., Jr, Seldin D. W. Acetazolamide in studying sodium reabsorption in diluting segment. Am J Physiol. 1970 Dec;219(6):1731–1738. doi: 10.1152/ajplegacy.1970.219.6.1731. [DOI] [PubMed] [Google Scholar]
  32. Seldin D. W., Rosin J. M., rector F. C., Jr Evidence against bicarbonate reabsorption in the ascending limb, particularly as disclosed by free-water clearance studies. Yale J Biol Med. 1975 Sep;48(4):337–347. [PMC free article] [PubMed] [Google Scholar]
  33. Stinebaugh B. J., Bartow S. A., Eknoyan G., Martinez-Maldonado M., Suki E. N. Renal handling of bicarbonate: effect of mannitol diuresis. Am J Physiol. 1971 May;220(5):1271–1274. doi: 10.1152/ajplegacy.1971.220.5.1271. [DOI] [PubMed] [Google Scholar]
  34. Stokes J. B. Consequences of potassium recycling in the renal medulla. Effects of ion transport by the medullary thick ascending limb of Henle's loop. J Clin Invest. 1982 Aug;70(2):219–229. doi: 10.1172/JCI110609. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Stoner L. C., Burg M. B., Orloff J. Ion transport in cortical collecting tubule; effect of amiloride. Am J Physiol. 1974 Aug;227(2):453–459. doi: 10.1152/ajplegacy.1974.227.2.453. [DOI] [PubMed] [Google Scholar]
  36. Ullrich K. J., Papavassiliou F. Bicarbonate reabsorption in the papillary collecting duct of rats. Pflugers Arch. 1981 Mar;389(3):271–275. doi: 10.1007/BF00584789. [DOI] [PubMed] [Google Scholar]
  37. Vurek G. G., Warnock D. G., Corsey R. Measurement of picomole amounts of carbon dioxide by calorimetry. Anal Chem. 1975 Apr;47(4):765–767. doi: 10.1021/ac60354a024. [DOI] [PubMed] [Google Scholar]
  38. Warnock D. G., Burg M. B. Urinary acidification: CO2 transport by the rabbit proximal straight tubule. Am J Physiol. 1977 Jan;232(1):F20–F25. doi: 10.1152/ajprenal.1977.232.1.F20. [DOI] [PubMed] [Google Scholar]

Articles from Journal of Clinical Investigation are provided here courtesy of American Society for Clinical Investigation

RESOURCES