Prakash, Y. S., H. F. M. van der Heijden, M. S. Kannan, and G. C. Sieck. Effects of salbutamol on intracellular calcium oscillations in porcine airway smooth muscle. J. Appl. Physiol. 82(6): 1836–1843, 1997.—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+]ioscillations 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+]ioscillations in freshly dissociated porcine ASM cells. Salbutamol decreased the frequency of [Ca2+]ioscillations in a concentration-dependent fashion, completely inhibiting the oscillations at 1 μM. 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+]ieven 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+]iresponse 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+]iby inhibiting Ca2+ influx through voltage-gated channels and by enhancing Ca2+ efflux.
The influence of interplay of external and internal noise on the detection of weak stimulus in a cell system
