Apical maxi-K (KCa1.1) channels mediate K+ secretion by the mouse submandibular exocrine gland

Tetsuji Nakamoto, Victor G. Romanenko, Atsushi Takahashi, Ted Begenisich, James E. Melvin

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)

Abstract

The exocrine salivary glands of mammals secrete K+ by an unknown pathway that has been associated with HCO3- efflux. However, the present studies found that K+ secretion in the mouse submandibular gland did not require HCO3-, demonstrating that neither K+/HCO3- cotransport nor K +/H+ exchange mechanisms were involved. Because HCO 3- did not appear to participate in this process, we tested whether a K channel is required. Indeed, K+ secretion was inhibited >75% in mice with a null mutation in the maxi-K, Ca 2+-activated K channel (KCa1.1) but was unchanged in mice lacking the intermediate-conductance IKCa1 channel (K Ca3.1). Moreover, paxilline, a specific maxi-K channel blocker, dramatically reduced the K+ concentration in submandibular saliva. The K+ concentration of saliva is well known to be flow rate dependent, the K+ concentration increasing as the flow decreases. The flow rate dependence of K+ secretion was nearly eliminated in K Ca1.1 null mice, suggesting an important role for KCa1.1 channels in this process as well. Importantly, a maxi-K-like current had not been previously detected in duct cells, the theoretical site of K+ secretion, but we found that KCa1.1 channels localized to the apical membranes of both striated and excretory duct cells, but not granular duct cells, using immunohistochemistry. Consistent with this latter observation, maxi-K currents were not detected in granular duct cells. Taken together, these results demonstrate that the secretion of K+ requires and is likely mediated by KCa1.1 potassium channels localized to the apical membranes of striated and excretory duct cells in the mouse submandibular exocrine gland.

Original languageEnglish
Pages (from-to)C810-C819
JournalAmerican Journal of Physiology - Cell Physiology
Volume294
Issue number3
DOIs
Publication statusPublished - 2008 Mar

Keywords

  • Calcium-activated K channels
  • Duct cells
  • Potassium secretion
  • Salivary gland

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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