Sarcoplasmic Reticulum Ca2+ Depletion by Caffeine and Changes of [Ca2+]i During Refilling in Bovine Airway Smooth Muscle Cells

The reverse mode of the Na+/Ca2+ exchanger provides a source of Ca2+ for store refilling following agonist-induced Ca2+ mobilization

“…However, ouabain alone had a biphasic effect on agonist-induced contractions, potentiating the early responses (responses [1][2][3][4][5] and attenuating the last two responses ( Fig. 3B; summarized in Fig.…”

“…Indeed, ASM displays cation conductances that reflect SOC activity and Cl Ϫ channels that contribute to increases in intracellular Na ϩ and membrane depolarization, respectively (13,14,16,17). Furthermore, the existence of the NCX in ASM is well established (2,20), and its functional existence in excitationcontraction has been reported recently (10). Thus it is plausible that Na ϩ influx following agonist-induced store depletion, in conjunction with membrane depolarization, could drive Ca 2ϩ influx through the reverse mode of the NCX.…”

Ionic mechanisms and Ca2+handling in airway smooth muscle

“…Interestingly, this conductance appeared to be constitutively active under ''resting'' conditions, and was likely to be responsible for the basal, nifedipine-insensitive, Ca 2+ influx pathway observed in this preparation [65]. Others have similarly reported the existence of a basal Ca 2+ influx pathway operating in ASM [121,122,124,125], speculating that this plasmalemmal Ca 2+ ''leak'' contributes to regulation of basal [Ca 2+ ] i [126].…”

Capacitative Ca^2+ Entry During Ca^2+ Undershoot in Bovine Airway Smooth Muscle

“…(Table 1). Caffeine peaks during genistein and Ni 2+ administration were significantly lower than the previous caffeine peak (P < 0.01 for Ni 2+ , n = 7; P <0.05 for genistein, n = 5; Table 1 undershoot is a common phenomenon in many cells, such as cardiac cells [6], smooth muscle cells [6,7,9,10], endothelial cells [19], and neurons [8,20]. This phenomenon can be trigger not only by caffeine but by noradrenaline [6], spontaneous Ca 2+ transients , ATP , acetylcholine [10] and electrical stimulation [6].…”

“…Strips were then transferred to a similar PSS containing fresh enzymes plus desoxyribonuclease I (1 mg/ml) until dispersed cells were observed. This procedure allows us to obtain cells with consistent levels of resting [Ca 2+ ] i [1,7]. The dispersed cells were loaded with 3 µM Fura-2 acetoxymethyl ester (AM) in low Ca 2+ (0.1 mM) for 1 hour at room temperature (22-25°C); then, cells were allowed to settle into a perfusion chamber with a glass cover in the bottom.…”