Hypo-osmotic potentiation of acetylcholine-stimulated ciliary beat frequency through ATP release in rat tracheal ciliary cells.
The ciliary beat frequency (CBF) of rat tracheal ciliary cells in a slice preparation was measured using video-enhanced contrast (VEC) microscopy. Acetylcholine (ACh) increased CBF mediated via intracellular Ca2+ concentration ([Ca2+]i) in a dose-dependent manner. An adequate hypo-osmotic stress (-40 mosM) potentiated ACh-stimulated CBF increase in tracheal ciliary cells and shifted the ACh dose-response curve to the left (lower concentration side). This potentiation was independent of hypo-osmotic stresses applied ranging from -20 mosM to -90 mosM. A hypo-osmotic stress induces ATP release in many cell types. The present study demonstrated that suramin (an inhibitor of purinergic receptors) and apyrase (an ATPase/ADPase) eliminate the hypo-osmotic potentiation of ACh-stimulated CBF increase and that ATP increased [Ca2+]i and CBF, as well as potentiating ACh-stimulated rises in [Ca2+]i and CBF increase. Moreover, the apical surface of tracheal ciliary cells were stained immunopositive for the P2X4 purinergic receptor. A hypo-osmotic stress (-40 mosM) transiently increased [Ca2+]i and potentiated the ACh-stimulated [Ca2+]i increase. The hypo-osmotic potentiation of ACh-stimulated CBF increase was not detected under Ca2+-free conditions. These observations suggest that a hypo-osmotic stress stimulates ATP release from the trachea. The released ATP may induce further increases in [Ca2+]i and CBF in ACh-stimulated tracheal ciliary cells, which may be mediated by purinergic receptors, such as P2X4.
Kawakami
Manpei
M
Department of Thoracic and Cardiovascular Surgery, Osaka Medical College, Takatsuki 569-8686, Japan.
Nagira
Tomoyoshi
T
Hayashi
Tetsuya
T
Shimamoto
Chikao
C
Kubota
Takahiro
T
Mori
Hiroshi
H
Yoshida
Hideyo
H
Nakahari
Takashi
T
D000109:Acetylcholine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002923:Cilia / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D018715:Microscopy, Video; D009994:Osmolar Concentration; D051381:Rats; D017208:Rats, Wistar; D014132:Trachea / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*
D000255:Adenosine Triphosphate; D000109:Acetylcholine; D002118:Calcium