title: Intact ability to lower urine pH in nonacidotic adrenalectomized rats.
abstract: Distal acidification was assessed in adrenalectomized (ADX) rats in which the development of acidosis was prevented by oral supplementation with NaHCO3, with or without glucocorticoid replacement. Totally corticosteroid-deficient nonacidotic rats were capable of lowering their urine pH in response to Na2SO4 infusion from a baseline of 7.47 +/- 0.22 to 4.83 +/- 0.1 (p less than 0.001). A similarly intact ability to lower the urine pH was also demonstrated in glucocorticoid-replaced mineralocorticoid-deficient rats. Absolute ammonium excretion was lower in ADX animals compared to controls (0.79 +/- 0.08 vs. 0.46 +/- 0.06 microEq/min, p less than 0.01) but when corrected for the difference in GFR, ammonium excretion was the same in ADX and adrenal-intact rats. During bicarbonate loading and at similar blood and urine pH, and bicarbonate concentrations, the U-B pCO2 gradient was similar in mineralocorticoid-deficient and adrenal intact rats (44 +/- 5.1 vs. 36 +/- 2.6 mm Hg, respectively). Amiloride administration to mineralocorticoid-deficient rats led to a reduction in the U-B pCO2 gradient from 30 +/- 4.5 to 10 +/- 3.0 mm Hg (p less than 0.002). These results indicate that the ability to lower the urine pH and raise the urine pCO2 is intact in the nonacidotic ADX rat; ammonium excretion in this model is reduced in proportion to the observed reduction in GFR, and amiloride administration inhibits acidification in ADX rats. The data strongly suggest the presence of a major site of aldosterone-independent, sodium-dependent acidification mechanism likely located at the level of the cortical collecting tubule.
mesh_terms: D000138:Acidosis / Q000517:prevention & control / Q000652:urine; D000315:Adrenalectomy; D000450:Aldosterone / Q000172:deficiency*; D000584:Amiloride / Q000627:therapeutic use; D000818:Animals; D001639:Bicarbonates / Q000627:therapeutic use; D003907:Dexamethasone / Q000627:therapeutic use; D006863:Hydrogen-Ion Concentration; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000627:therapeutic use; D017693:Sodium Bicarbonate; D012965:Sodium Chloride / Q000627:therapeutic use; D013431:Sulfates / Q000627:therapeutic use; D014556:Urine / Q000032:analysis*
chemical_list: D001639:Bicarbonates; D013431:Sulfates; C012036:sodium sulfate; D012965:Sodium Chloride; D000450:Aldosterone; D000584:Amiloride; D003907:Dexamethasone; D017693:Sodium Bicarbonate; D012964:Sodium