Superficial buffer barrier and preferentially directed release of Ca2+ in canine airway smooth muscle

We examined cytosolic concentration of Ca²⁺ ([Ca²⁺](i)) in canine airway smooth muscle using fura 2 fluorimetry (global changes in [Ca²⁺](i)), membrane currents (subsarcolemmal [Ca²⁺](i)), and contractions (deep cytosolic [Ca²⁺](i)). Acetylcholine (10^-4 M) elicited fluorimetric, electrophysiological, and mechanical responses. Caffeine (5 mM), ryanodine (0.1-30 μM), and 4-chloro-3-ethylphenol (0.1-0.3 mM), all of which trigger Ca²⁺-induced Ca²⁺ …