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

Abstract

Chronic hypokalemia increases the activity of proximal tubule apical membrane Na+/H+ antiporter NHE3. The present study examined the effect of the incubation of OKP cells (an opossum kidney, clone P cell line) in control medium (K+ concn ([K+]) = 5.4 mM) or low-K+ medium ([K+] = 2.7 mM) on NHE3. The activity of an ethylisopropyl amiloride-resistant Na+/H+ antiporter, whose characteristics were consistent with those of NHE3, was increased in low-K+ cells beginning at 8 h. NHE3 mRNA and NHE3 protein abundance were increased 2.2-fold and 62%, respectively, at 24 h but not at 8 h. After incubation in low-K+ medium, intracellular pH (pHi) decreased by 0.27 pH units (maximum at 27 min) and then recovered to the control level. Intracellular acidosis induced by 5 mM sodium propionate increased Na+/H+ antiporter activity at 8 and 24 h. Herbimycin A, a tyrosine kinase inhibitor, blocked low-K+- and sodium propionate-induced activation of the Na+/H+ antiporter at 8 and 24 h. Our results demonstrate that low-K+ medium causes an early decrease in pHi, which leads to an increase in NHE3 activity via a tyrosine kinase pathway.

• Authors: M Amemiya, K Tabei, E Kusano, Y Asano, R J Alpern
• Journal: The American journal of physiology (Am J Physiol) Vol. 276 Issue 3 Pg. C711-6 (03 1999) ISSN: 0002-9513 [Print] United States
• PMID: 10069999 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Acids
• Culture Media
• RNA, Messenger
• Sodium-Hydrogen Exchanger 3
• Sodium-Hydrogen Exchangers
• Hydrogen
• Protein-Tyrosine Kinases
• Potassium

Topics

• Acids (metabolism)
• Animals
• Cell Line
• Culture Media (chemistry, pharmacology)
• Hydrogen (metabolism)
• Hydrogen-Ion Concentration
• Intracellular Membranes (metabolism)
• Kidney (cytology, drug effects, metabolism)
• Opossums
• Potassium (administration & dosage, pharmacology)
• Protein-Tyrosine Kinases (metabolism)
• RNA, Messenger (metabolism)
• Sodium-Hydrogen Exchanger 3
• Sodium-Hydrogen Exchangers (genetics, metabolism)
• Time Factors