Modulation of the Ca2+ sensitivity of airway smooth muscle cells in murine lung slices.
To investigate the phenomenon of Ca(2+) sensitization, we developed a new intact airway and arteriole smooth muscle cell (SMC) "model" by treating murine lung slices with ryanodine-receptor antagonist, ryanodine (50 microM), and caffeine (20 mM). A sustained elevation in intracellular Ca(2+) concentration ([Ca(2+)](i)) was induced in both SMC types by the ryanodine-caffeine treatment due to the depletion of internal Ca(2+) stores and the stimulation of a persistent influx of Ca(2+). Arterioles responded to this sustained increase in [Ca(2+)](i) with a sustained contraction. By contrast, airways responded to sustained high [Ca(2+)](i) with a transient contraction followed by relaxation. Subsequent exposure to methacholine (MCh) induced a sustained concentration-dependent contraction of the airway without a change in the [Ca(2+)](i). During sustained MCh-induced contraction, Y-27632 (a Rho-kinase inhibitor) and GF-109203X (a protein kinase C inhibitor) induced a concentration-dependent relaxation without changing the [Ca(2+)](i). The cAMP-elevating agents, forskolin (an adenylyl cyclase activator), IBMX (a phosphodiesterase inhibitor), and caffeine (also acting as a phosphodiesterase inhibitor), exerted similar relaxing effects. These results indicate that 1) ryanodine-caffeine treatment is a valuable tool for investigating the contractile mechanisms of SMCs while avoiding nonspecific effects due to cell permeabilization, 2) in the absence of agonist, sustained high [Ca(2+)](i) has a differential time-dependent effect on the Ca(2+) sensitivity of airway and arteriole SMCs, 3) MCh facilitates the contraction of airway SMCs by inducing Ca(2+) sensitization via the activation of Rho-kinase and protein kinase C, and 4) cAMP-elevating agents contribute to the relaxation of airway SMCs through Ca(2+) desensitization.
Bai
Yan
Y
Department of Physiology, University of Massachusetts Medical School, Worcester, 01655, USA.
Sanderson
Michael J
MJ
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000166:cytology / Q000378:metabolism; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012137:Respiratory System / Q000033:anatomy & histology* / Q000378:metabolism; D012433:Ryanodine / Q000494:pharmacology
D016085:Bronchoconstrictor Agents; D000697:Central Nervous System Stimulants; D004791:Enzyme Inhibitors; D016210:Methacholine Chloride; D012433:Ryanodine; D005576:Colforsin; D002110:Caffeine; D000242:Cyclic AMP; D011493:Protein Kinase C; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine