Received September 21, 2004
Revised November 17, 2004
Accepted after revision March 4, 2005

¹ Osaka Medical College

^* To whom correspondence should be addressed. E-mail: takan{at}art.osaka-med.ac.jp.

	Abstract

Ciliary beat frequency (CBF) was measured by video-optical microscopy in rat tracheal and distal airway ciliary cells using a slice preparation. In tracheal ciliary cells (tracheal slice), ATP or 2-methylthio ATP (MeSATP) increased CBF, which was inhibited by suramin (100 µM, an inhibitor of purinergic receptor). Ionomycin (5 µM) or thapsigargin (2 µM) increased CBF similarly. A Ca²⁺-free solution or Ni²⁺ (1 mM) decreased CBF gradually by approximately 25 % and the subsequent stimulation with ATP (10µM) increased CBF transiently. The purinergic agonist study demonstrated that ATP increases CBF in tracheal ciliary cells via both P2X and P2Y receptors. ATP increased the intracellular calcium concentration ([Ca²⁺]_i) in tracheal ciliary cells. However, in distal airway ciliary cells (lung slice), ATP did not increase CBF and[Ca²⁺]_i, although a Ca²⁺-free solution decreased CBF and ionomycin (5 µM) or thapsigargin (2 µM) increased it. Moreover, acetylcholine (100 µM) did not increase CBF in distal airway ciliary cells, although it increased CBF in tracheal ciliary cells. Terbutaline (10 µM), a ₂-selective agonist, increased CBF in both tracheal and distal airway ciliary cells. These observations suggest that the Ca²⁺-mobilization mechanisms via purinergic or muscarinic receptors of the distal airway ciliary cell may be different from those of the tracheal ciliary cell. In conclusion, the CBF increase is differently regulated in the trachea and distal airways of the rat.

Key Words: Airway, ATP, Cilium