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.
DOI of Published Version
Am J Physiol Lung Cell Mol Physiol. 2006 Aug;291(2):L208-21. Epub 2006 Feb 3. Link to article on publisher's site
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.