Carbonic anhydrase independent bicarbonate reabsorption in rats with chronic papillary necrosis
Cruz-Soto, M.; Frommer, J.P.; Itsarayoungyuen, K.; Batlle, D.C.; Arruda, J.A.; Kurtzman, N.A.
Mineral and Electrolyte Metabolism 10(5): 319-325
1984
ISSN/ISBN: 0378-0392 PMID: 6436656 Document Number: 221482
An attempt was made to indirectly localize the tubular sites of carbonic anhydrase independent bicarbonate reabsorption in the rat. Papillary necrosis was induced in rats by i.v. administration of bromoethyleneamine hydrobromide (BEA) 6 wk prior to the study, in order to assess the role of deep nephrons in this process. Acetazolamide alone, acetazolamide plus amiloride, and acetazolamide, amiloride plus furosemide were infused into rats with intact papillae (groups I, III, V) and rats with BEA-induced papillary necrosis (groups II, IV, VI). Chronic papillary necrosis evidently does not alter carbonic anhydrase independent bicarbonate reabsorption, since the fractional excretion of bicarbonate (FEHCO3)) was not significantly higher when acetazolamide was infused into animals with BEA-induced papillary necrosis as compared to those rats with intact papillae (FEHCO3 group I vs. group II; NS . The addition of amiloride hydrochloride, a blocker of distal acidification at the administered doses, increased FEHCO3 significantly in both animals with intact papillae and those with papillary necrosis to a similar degree. The addition of furosemide to acetazolamide and amiloride further induced a significant increase in FEHCO3 only in the group of animals with papillary necrosis (FEHCO3 group V 43.0 .+-. 2.9% vs. group VI 52.1 .+-. 0.9%; P < 0.05). Deeper nephrons and papillary strutures apparently are not indispensable for carbonic anhydrase independent bicarbonate reabsorption in the rat on a chronic basis. The cortical collecting duct appears to have significant capacity to reabsorb bicarbonate independent of carbonic anhydrase which can be blocked by amiloride. There appear to be segments of the nephron which reabsorb bicarbonate independently of carbonic anhydrase activity and are sensitive to furosemide. This effect of furosemide was uncovered in animals in which chronic papillary necrosis was induced with BEA.