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Related Experiment Videos

Incubation of OKP cells in low-K+ media increases NHE3 activity after early decrease in intracellular pH.

M Amemiya1, K Tabei, E Kusano

  • 1Division of Nephrology, Department of Internal Medicine, Jichi Medical School, Tochigi, Japan 329-0498, USA.

The American Journal of Physiology
|March 10, 1999
PubMed
Summary

Chronic low potassium (hypokalemia) increases proximal tubule Na+/H+ antiporter NHE3 activity. This occurs through an early intracellular acidosis, activating NHE3 via a tyrosine kinase pathway, leading to increased NHE3 expression.

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Area of Science:

  • Nephrology
  • Cell Physiology
  • Molecular Biology

Background:

  • Chronic hypokalemia is known to increase the activity of the proximal tubule apical membrane Na+/H+ antiporter, NHE3.
  • The opossum kidney (OKP) cell line provides a model to study cellular responses to potassium levels.

Purpose of the Study:

  • To investigate the effects of low potassium (hypokalemia) on NHE3 activity, expression, and the underlying mechanisms in OKP cells.
  • To determine if intracellular acidosis plays a role in hypokalemia-induced NHE3 activation.

Main Methods:

  • OKP cells were incubated in control or low-potassium media.
  • Na+/H+ antiporter activity was measured using ethylisopropyl amiloride-resistant uptake.
  • NHE3 mRNA and protein levels were quantified.

Related Experiment Videos

  • Intracellular pH (pHi) was monitored.
  • Effects of induced intracellular acidosis and tyrosine kinase inhibition were assessed.

    • Main Results:

    • Low-potassium incubation increased NHE3 activity starting at 8 hours.
    • NHE3 mRNA and protein abundance increased significantly at 24 hours but not at 8 hours.
    • Low potassium caused an initial decrease in pHi, followed by recovery.
    • Induced intracellular acidosis mimicked the effect of low potassium on antiporter activity.
    • Herbimycin A (a tyrosine kinase inhibitor) blocked the activation of NHE3.

    Conclusions:

    • Low-potassium conditions lead to an early intracellular acidosis in OKP cells.
    • This acidosis triggers an increase in NHE3 activity.
    • The activation of NHE3 by low potassium involves a tyrosine kinase-dependent pathway.
    • These findings elucidate a key mechanism in the renal response to hypokalemia.