Acetylcholine-induced calcium signaling and contraction of airway smooth muscle cells in lung slices.
The Ca(2+) signaling and contractility of airway smooth muscle cells (SMCs) were investigated with confocal microscopy in murine lung slices (approximately 75-microm thick) that maintained the in situ organization of the airways and the contractility of the SMCs for at least 5 d. 10--500 nM acetylcholine (ACH) induced a contraction of the airway lumen and a transient increase in [Ca(2+)](i) in individual SMCs that subsequently declined to initiate multiple intracellular Ca(2+) oscillations. These Ca(2+) oscillations spread as Ca(2+) waves through the SMCs at approximately 48 microm/s. The magnitude of the airway contraction, the initial Ca(2+) transient, and the frequency of the subsequent Ca(2+) oscillations were all concentration-dependent. In a Ca(2+)-free solution, ACH induced a similar Ca(2+) response, except that the Ca(2+) oscillations ceased after 1--1.5 min. Incubation with thapsigargin, xestospongin, or ryanodine inhibited the ACH-induced Ca(2+) signaling. A comparison of airway contraction with the ACH-induced Ca(2+) response of the SMCs revealed that the onset of airway contraction correlated with the initial Ca(2+) transient, and that sustained airway contraction correlated with the occurrence of the Ca(2+) oscillations. Buffering intracellular Ca(2+) with BAPTA prohibited Ca(2+) signaling and airway contraction, indicating a Ca(2+)-dependent pathway. Cessation of the Ca(2+) oscillations, induced by ACH-esterase, halothane, or the absence of extracellular Ca(2+) resulted in a relaxation of the airway. The concentration dependence of the airway contraction matched the concentration dependence of the increased frequency of the Ca(2+) oscillations. These results indicate that Ca(2+) oscillations, induced by ACH in murine bronchial SMCs, are generated by Ca(2+) release from the SR involving IP(3)- and ryanodine receptors, and are required to maintain airway contraction.
Bergner
Albrecht
A
Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Sanderson
Michael J
MJ
D000109:Acetylcholine / Q000494:pharmacology* / Q000502:physiology; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008168:Lung / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000502:physiology*
D000109:Acetylcholine