Abstract
Relaxation of airway smooth muscle (ASM) by β-adrenoceptor agonists involves reduction of intracellular Ca2+ concentration ([Ca2+](i)). In porcine ASM cells, acetylcholine induces [Ca2+](i) oscillations that display frequency modulation by agonist concentration and basal [Ca2+](i). We used real-time confocal microscopy to examine the effect of salbutamol (1 nM to 1 μM), a β2-adrenoceptor agonist, on [Ca2+](i) oscillations in freshly dissociated porcine ASM cells. Salbutamol decreased the frequency of [Ca2+](i) oscillations in a concentration-dependent fashion, completely inhibiting the oscillations at 1μM. These effects were mimicked by a cell- permeant analog of adenosine 3',5'-cyclic monophosphate. The inhibitory effect of salbutamol was partially reversed by BAY K 8644. Salbutamol reduced [Ca2+)(i) even when sarcoplasmic reticulum (SR) Ca2+ reuptake and Ca2+ influx were blocked. Lanthanum blockade of Ca2+ efflux attenuated the inhibitory effect of salbutamol on [Ca2+](i). The [Ca2+](i) response to caffeine was unaffected by salbutamol. On the basis of these results, we conclude that β2-adrenoceptor agonists have little effect on SR Ca2+ release in ASM cells but reduce [ Ca2+](i) by inhibiting Ca2+ influx through voltage-gated channels and by enhancing Ca2+ efflux.
Original language | English (US) |
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Pages (from-to) | 1836-1843 |
Number of pages | 8 |
Journal | Journal of applied physiology |
Volume | 82 |
Issue number | 6 |
DOIs | |
State | Published - Jun 1997 |
Keywords
- Asthma
- Calcium channel
- Calcium efflux
- Confocal imaging
- β-adrenoceptor agonists
ASJC Scopus subject areas
- Physiology
- Physiology (medical)