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1 Division of Pulmonary and Critical Care Medicine
2 Department of Cell Biology and Anatomy, University of Miami School of Medicine, Miami, FL 33136, USA
3
Department of Respiratory Medicine, Semmelweis University, Budapest, Hungary
pHi affects a number of cellular functions, but the influence of pHi on mammalian ciliary beat frequency (CBF) is not known. CBF and pHi of single human tracheobronchial epithelial cells in submerged culture were measured simultaneously using video microscopy (for CBF) and epifluorescence microscopy with the pH-sensitive dye BCECF. Baseline CBF and pHi values in bicarbonate-free medium were 7.2 ± 0.2 Hz and 7.49 ± 0.02, respectively (n = 63). Alkalization by ammonium pre-pulse to pHi 7.78 ± 0.02 resulted in a 2.2 ± 0.1 Hz CBF increase (P < 0.05). Following removal of NH4Cl, pHi decreased to 7.24 ± 0.02 and CBF to 5.8 ± 0.1 Hz (P < 0.05). Removal of extracellular CO2 to change pHi resulted in similar CBF changes. Pre-activation of cAMP-dependent protein kinase (10 µM forskolin), broad inhibition of protein kinases (100 µM H-7), inhibition of PKA (10 µM H-89), nor inhibition of phosphatases (10 µM cyclosporin + 1.5 µM okadaic acid) changed pHi-mediated changes in CBF, nor were they due to [Ca2+]i changes. CBF of basolaterally permeabilized human tracheobronchial cells, re-differentiated at the air–liquid interface, was 3.9 ± 0.3, 5.7 ± 0.4, 7.0 ± 0.3 and 7.3 ± 0.3 Hz at basolateral i.e., intracellular pH of 6.8, 7.2, 7.6 and 8.0, respectively (n = 18). Thus, intracellular alkalization stimulates, while intracellular acidification attenuates human airway CBF. Since phosphorylation and [Ca2+]i changes did not seem to mediate pHi-induced CBF changes, pHi may directly act on the ciliary motile machinery.
(Received 14 May 2004;
accepted after revision 6 August 2004;
first published online 12 August 2004)
Corresponding author M. Salathe: Division of Pulmonary and Critical Medicine (R-47), University of Miami School of Medicine, 1600 NW 10th Avenue, RMSB 7063 Miami, FL 33136, USA. Email: msalathe{at}miami.edu
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