Hypertrophy of proximal tubular epithelial cells induced by low pH in vitro is independent of ammoniagenesis.
Metabolic acidosis can lead to tubular hypertrophy in vivo. This is thought to arise from stimulation of renal production of ammonia, a known hypertrophic agent. To examine this effect in vitro, confluent opossum (OK) proximal tubular epithelial cells were cultured at acidic pH (7.21 +/- 0.02) or at control pH (7.37 +/- 0.01) for 4 days. Protein content was 9% higher at acidic pH whereas DNA content was unaffected. The resulting increase in mean cell size (protein/DNA ratio) was 10% but correlated inversely with the mass of cells in control wells, varying from +48% at low cell mass to -14% at high cell mass. In contrast, low pH decreased 3H-thymidine incorporation by 9%. However, ammonia production was unaffected. These changes in protein/DNA ratio and 3H-thymidine incorporation cannot therefore be attributed to acid-induced ammoniagenesis and imply that low pH exerts a more direct effect on tubular cell growth than previously envisaged.
Bevington
A
A
Department of Nephrology, Leicester General Hospital, UK.
Millwater
C J
CJ
Walls
J
J
D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D002455:Cell Division; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism / Q000473:pathology; D006863:Hydrogen-Ion Concentration; D006984:Hypertrophy / Q000378:metabolism / Q000473:pathology; D007687:Kidney Tubules, Proximal / Q000378:metabolism* / Q000473:pathology*; D009893:Opossums; D012964:Sodium / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D014316:Tritium
D014316:Tritium; D000641:Ammonia; D004247:DNA; D012964:Sodium; D013936:Thymidine