Modulation of the Ca2+ sensitivity of airway smooth muscle cells in murine lung slices
Department of Physiology
1-Methyl-3-isobutylxanthine; Animals; Arterioles; Bronchoconstrictor Agents; Caffeine; Calcium; Central Nervous System Stimulants; Cyclic AMP; Enzyme Inhibitors; Forskolin; Male; Methacholine Chloride; Mice; Mice, Inbred BALB C; Muscle Contraction; Myocytes, Smooth Muscle; Protein Kinase C; Respiratory System; Ryanodine
Life Sciences | Medicine and Health Sciences
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.
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Citation: Am J Physiol Lung Cell Mol Physiol. 2006 Aug;291(2):L208-21. Epub 2006 Feb 3. Link to article on publisher's site
DOI of Published Version
American journal of physiology. Lung cellular and molecular physiology
Bai, Yan and Sanderson, Michael J., "Modulation of the Ca2+ sensitivity of airway smooth muscle cells in murine lung slices" (2006). Open Access Articles. 129.