Effect of Chronic Metabolic Acidosis on Renal Growth and Renal Sodium Handling in Uninephrectomized Rats

Abstract

Paucity studies have indicated that a systemic metabolic acidosis cause a decrease in salt and water reabsorption in the kidney. The following study was undertaken on male Wistar-Hannover rats (200–250 g) to investigate the effects of a chronic, NH₄Cl-induced metabolic acidosis on the renal handling of Na⁺ in sham-operated and uninephrectomized rats, by lithium clearance. The present study shows that chronic acidosis (blood pH, 7.16 ± 0.13) caused a sustained increase in renal fractional Na⁺ excretion (267.9 ± 36.4%), accompanied by a rise in the fractional proximal (113.3 ± 3.6%) and post-proximal (179.7 ± 20.2%) Na⁺ and fractional K⁺ (163.4 ± 5.6%) excretions when compared to pair-fed rats. These differences occurred in spite of an unchanged creatinine clearance and Na⁺ filtered load. On the other hand, a body growth impairment was observed in the acidotic (control, 258 ± 3.7 g versus acidotic, 232 ± 4.6 g) and pair-fed rats (225 ± 3.6 g), whereas there was significant enhance in the kidney weights in acidotic rats (1.73 ± 0.05 g) compared to other experimental groups (control, 1.46 ± 0.05 g; pair-fed, 1.4 ± 0.05 g). The renal growth indexes aftr metabolic acidosis NH₄Cl-induced did not shown statistical difference at 1.5, 3.0 and 12 hours after uninephrectomy when were compared with pair-fed groups. However, from the fjfth to tenth day after unilateral nephrectomy the renal growth index of acidotic group was significantly greater than pair-fed groups. Unilateral nephrectomy in acidotic animals caused a striking additional but transient increase in fractional renal sodium (FENa⁺) and potassium (FEK⁺) excretion from 1.5 to 3 hours post-surgery meanly associated with an enhanced post-proximal sodium excretion when compared to pair-fed uninephrectomize rats. By the fifth postoperative day the all functional values returned to baseline levels. This altered renal Na⁺ handling and K⁺ excretion may result from a reciprocal relationship between tubular metabolic pathway stimuli and ion transport. Further studies are required to investigate the acidosis involvement on functional kidney response.

Key Words:

• Renal function
• Renal sodium excretion
• Lithium clearance
• Metabolic acidosis