Regulation of adenosine 5'-triphosphate (ATP)-gated P2X(4) receptors on tracheal smooth muscle cells.
We examined the effects of extracellular adenosine 5'-triphosphate (ATP) on single airway smooth muscle (ASM) cells from porcine trachea using a patch-clamp technique. ATP induced a sustained inward current. Phospholipase C inhibitor U-73122 failed to inhibit the current, suggesting the involvement of P2X receptor. A specific effecter of P2X(4), ivermectin, augmented the current indicating the existence of P2X(4) receptors. Immunohistochemistry and reverse transcription/polymerase chain reaction analysis and Western blot analysis also showed the distribution of the P2X(4) receptors. The inward current was reduced by SKF-96365, an inhibitor of both voltage-dependent Ca(2+) channels (VDCCs) and voltage-independent Ca(2+) channels, although a VDCC antagonist, verapamil, did not affect the current. SKF-96365 caused complete suppression of both the increase in the intracellular Ca(2+) concentration and the contraction of ASM cells induced by ATP. Our results demonstrate that P2X(4) receptors exist on ASM and that the receptors are responsible for Ca(2+) influx. These findings suggest that the Ca(2+) influx regulated by P2X(4) receptors plays an important role in ASM contraction by a pathway distinct from VDCC.
Division of Infectious and Respiratory Diseases, Department of Internal Medicine, Tohoku University School of Medicine, Aoba-ku, Sendai, Japan.
Miyuki
M
Nagaoka
Masayuki
M
Nara
Tsutomu
T
Tamada
Hiroaki
H
Kume
Tetsuya
T
Oguma
Toshiaki
T
Kikuchi
Jamal
J
Zaini
Takuya
T
Moriya
Masakazu
M
Ichinose
Gen
G
Tamura
Toshio
T
Hattori
D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects*; D007093:Imidazoles / Q000494:pharmacology; D007559:Ivermectin / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques / Q000379:methods; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058848:Receptors, Purinergic P2X4; D013498:Suramin / Q000494:pharmacology; D013552:Swine; D014132:Trachea / Q000166:cytology*; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D007093:Imidazoles; D010975:Platelet Aggregation Inhibitors; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D013498:Suramin; D007559:Ivermectin; D000255:Adenosine Triphosphate; D014700:Verapamil; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium