Differentiation of proton-pumping activity in cultured renal inner medullary collecting duct cells

Luc P. Brion, John H. Schwartz, Beth J. Zavilowitz, George J. Schwartz

Research output: Contribution to journalArticlepeer-review


Cultured inner medullary collecting duct (IMCD) cells have been shown to secrete protons (H+) by two mechanisms: an N-ethylmaleimide-and dicyclohexyl-carbodiimide-sensitive electrogenic H+-ATPase or H+ pump, and an amiloride-sensitive, secondary active Na+/H+ exchanger. These cells also express Cl-/HCO3- exchange and carbonic anhydrase activity in common with other renal epithelial cells involved in acid-base transport. Video fluorescence microscopy of individual cells using 2′, 7′-biscarboxyethyl-5(6)-carboxyfluorescein has demonstrated that adjacent-cultured IMCD cells show substantial functional intercellular heterogeneity. The development of H+-pumping activity is associated with high-baseline intracellular pH and peanut agglutinin (PNA) affinity, and loss of mitotic activity and of Na+/H+ exchange. The H+-pumping activity may be further enhanced by removal of fetal calf serum for 6-54 h or by selecting cells with high PNA affinity. IMCD cells in their most differentiated state form domes, which consistently showed the highest rates of H+-pumping activity, as well as high affinity for peanut lectin. When IMCD were plated at low density, domes developed relatively late (2-4 weeks), at which time cells located in the center of nests of contiguously growing cells were quiescent and showed H+-pumping activity but no Na+/H+ exchange. On the other hand, dense plating was associated with early development of domes (end of 1st week), at which time adjacent cells showed a high mitotic activity and Na+/H+ exchange, but no H+-pumping activity. We speculate that differentiation of IMCD cells results in the development of cell polarity. This could include either loss of the apical Na+/H+-exchange activity, or localization of this exchanger only to the basolateral membrane, while the H+ pump differentiates at the apical membrane.

Original languageEnglish (US)
Pages (from-to)408-414
Number of pages7
JournalPediatric Nephrology
Issue number4
StatePublished - Jul 1990


  • Acidification
  • Inner medullary collecting duct
  • Na/H exchange
  • Peanut agglutinin
  • Proton ATPase
  • Proton-pumping activity
  • Video fluorescence microscopy

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Nephrology


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