Capacitative Ca2+ entry during Ca2+ undershoot in bovine airway smooth muscle.
In numerous cells, Ca2+ undershoot is commonly observed after withdrawing stimulus that release Ca2+ from intracellular stores. In airway smooth muscle (ASM), the fast intracellular Ca2+ concentration ([Ca2+]i) drop during undershoot is produced by sarcoplasmic reticulum (SR) reloading, but the mechanisms involved in the long lasting basal [Ca2+]i recovery are unknown. We investigated the post-caffeine Ca2+ undershoot recovery in ASM isolated cells from bovine trachea. [Ca2+]i determination was done by a ratiometric method by incubating cells with Fura-2/AM. After inducing a transient response, caffeine withdrawn generated a Ca2+ undershoot. SR-Ca2+ content during maximum undershoot drop was approximately 40% of SR caffeine-releasable Ca2+ (SR-Ca2+ load). Undershoot recovery rate increased in presence of cyclopiazonic acid (CPA, a SR-Ca2+ ATPase inhibitor), but SR-Ca2+ load was reduced. Genistein (a tyrosine kinase inhibitor) slowed down the Ca2+ undershoot drop and the SR-Ca2+ load but did not affect the undershoot recovery rate. Ni2+ (a capacitative Ca2+ inhibitor), but neither SKF-96365 (a passive Ca2+ entry inhibitor) nor econazole (a capacitative Ca2+ inhibitor in non-excitable cells), inhibited Ca2+ undershoot recovery and SR-Ca2+ load. Our data suggest that capacitative Ca2+ entry is involved in bovine ASM Ca2+ undershoot recovery, and that changes in Ca2+ undershoot have an impact on SR-Ca2+ loading which might affect in turn ASM excitability.
Bazán-Perkins
Blanca
B
Departamento de Hiperreactividad Bronquial, Instituto Nacional de Enfermedades Respiratorias, Ismael Cosío Villegas, Mexico DF. perkins@unam.mx
Sánchez-Guerrero
Edgar
E
Campos
María G
MG
D000818:Animals; D002110:Caffeine / Q000378:metabolism / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002412:Cations / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D004464:Econazole / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D019833:Genistein / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D009532:Nickel / Q000494:pharmacology; D048789:Phytoestrogens / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013997:Time Factors; D014132:Trachea / Q000166:cytology*
D002121:Calcium Channel Blockers; D002412:Cations; D005456:Fluorescent Dyes; D007093:Imidazoles; D007211:Indoles; D007476:Ionophores; D048789:Phytoestrogens; D002110:Caffeine; D015759:Ionomycin; D004464:Econazole; D009532:Nickel; D019833:Genistein; D000252:Calcium-Transporting ATPases; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium; D016257:Fura-2; C000543:cyclopiazonic acid