Extracellular ATP induces hyperpolarization and motility stimulation of ciliary cells

Abstract

Cellular membrane potential and ciliary motility were examined in tissues cultures prepared from frog palate and esophagus epithelia. Addition of micromolar concentrations of extracellular ATP caused membrane hyperpolarization and enhanced the beat frequency. These two effects of ATP were 1) dose dependent, reaching a maximum at 10 microM ATP; 2) dependent on the presence of extracellular Ca2+ or Mg2+; 3) insensitive to inhibitors of voltage-gated calcium channels; 4) abolished after depleting the intracellular Ca2+ stores with thapsigargin; 5) attenuated by quinidine (1 mM), Cs+ (5-20 mM), and replacement of extracellular Na+ by K+; 6) insensitive to charybdotoxin (5-20 nM), TEA (1-20 microM), and apamin (0.1-1 microM); 7) independent of initial membrane potential; and 8) unaffected by amiloride. In addition, extracellular ATP induced an appreciable rise in intracellular Ca2+. Addition of thapsigargin caused an initial enhancement of the ciliary beat frequency and membrane hyperpolarization. These results strongly suggest the involvement of calcium-dependent potassium channels in the response to ATP. The results show that moderate hyperpolarization is closely associated with a sustained enhancement of ciliary beating by extracellular ATP.

Epithelial P2X purinergic receptor channel expression and function

“…Tarasiuk et al and Korngreen et al have also shown that extracellular ATP may enhance ciliary beat frequency in a P2XR-dependent manner (8,27). Enhancement of ciliary beat would also be beneficial for mucociliary clearance therapy in CF.…”

Purinergic signalling in the gastrointestinal tract and related organs in health and disease

“…ATP enhances ciliary beat frequency two-to threefold and induces pronounced changes in the metachronal wave parameters [269]. In addition, membrane fluidisation was induced, and increases in cytosolic Ca 2+ , principally from internal stores, coupled to membrane hyperpolarisation were necessary to activate all these cellular effects [9,655]. Studies from this group have also established the existence of two P2 receptors, one of which is probably a P2Y receptor [270] and that the actions of ATP depends on PKC producing sustained enhancement of ciliary beat frequency via activation of calcium influx through non-voltage-operated Ca 2+ channels [437].…”

Enhancement of Ca2+ Influx and Ciliary Beating by Membrane Hyperpolarization due to ATP-Sensitive K+ Channel Opening in Mouse Airway Epithelial Cells

“…Although the expression of K ATP channels has been reported in alveolar cells (Trinh et al, 2007) and cell lines derived from human airway epithelial tissues (Trinh et al, 2008), their functional expression in ciliary cells has not yet been documented. Previous studies have revealed that ATP and acetylcholine are major endogenous stimulants that facilitate ciliary beating by activating the purinoceptors and by increasing [Ca 21 ] i , which, in turn, may induce membrane hyperpolarization via the activation of Ca 21 -dependent K 1 channels (Weiss et al, 1992;Tarasiuk et al, 1995). However, conflicting reports have been published on whether changes in the membrane potential can significantly affect the ciliary beat frequency (Ma et al, 2002).…”