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Maleic acid-induced proximal tubulopathy: Na:K pump inhibition

S K Mujais1

  • 1Department of Medicine, Northwestern University, Chicago, IL.

Journal of the American Society of Nephrology : JASN
|August 1, 1993
PubMed

Insights

Maleic acid (MA) causes temporary kidney damage, specifically affecting the sodium-potassium (Na:K) pump in the proximal convoluted tubule (PCT). This impairment in the Na:K pump and metabolic function recovers within 24 hours.

Area of Science:

  • Nephrology
  • Renal Physiology
  • Biochemistry

Background:

  • Maleic acid (MA) is a known nephrotoxin that induces a reversible renal tubule dysfunction resembling Fanconi's syndrome in experimental models.
  • Understanding the specific cellular mechanisms and the site of MA-induced kidney injury is crucial for defining therapeutic targets.

Purpose of the Study:

  • To investigate the alterations in the sodium-potassium (Na:K) pump activity along the nephron during the development and recovery from maleic acid injury.
  • To correlate changes in Na:K pump function with metabolic alterations in the kidney.

Main Methods:

  • Male Sprague Dawley rats were administered maleic acid (100 mg/kg iv).
  • Na:K pump activity was measured in different segments of the nephron at baseline, 2 hours, and 24 hours post-administration.
  • Oxidative metabolism (14CO2 formation from glutamine) was assessed in proximal convoluted tubule segments.

Main Results:

  • Maleic acid induced a rapid and reversible decline in Na:K pump activity specifically in the proximal convoluted tubule (PCT).
  • No significant changes in Na:K pump activity were observed in other nephron segments (pars rectae, thick ascending limb, collecting tubules).
  • A transient decrease in glutamine oxidation was observed in PCTs 2 hours after MA administration, indicating impaired metabolic function.

Conclusions:

  • Maleic acid causes a reversible, segment-specific impairment of the Na:K pump in the PCT.
  • This impairment in Na:K pump activity is paralleled by a reduction in oxidative metabolism.
  • These findings suggest that MA-induced proximal tubulopathy involves early, reversible damage to PCT Na:K pump function and metabolism.

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