Published ahead of print on August 24, 2006, doi:10.1165/rcmb.2006-0036OC Am. J. Respir. Cell Mol. Biol., Volume 36, Number 1, January 2007, 122-130 A more recent version of this article appeared on January 1, 2007
Submitted on January 26, 2006 Contractility and Ca2+ Signaling of Smooth Muscle Cells in Different Generations of Mouse AirwaysYan Bai1,1 Department of Physiology, University of Massachusetts Medical School, Worcester, MA, USA * To whom correspondence should be addressed. E-mail: Michael.sanderson{at}umassmed.edu.
The control and mechanisms of airway smooth muscle cell (SMC) contraction were investigated with a sequential series of lung slices from different generations of the same airway from the cardiac lobe of the mouse lung. Airway contraction was measured by monitoring the changes in airway lumen area with phase-contrast microscopy. Changes in intracellular calcium concentration of the SMCs were studied with a custom-built confocal or two-photon microscope. The distribution of the airway SMCs and the muscarinic M3 or 5-HT2A receptors was determined with immuno-fluorescence. Methacholine and 5-HT induced a concentration-dependent airway contraction and Ca2+ oscillations within the SMCs of each airway generation. The airway contraction in response to the same agonist concentration was greater in the middle generation as compared to the distal or proximal generations of the same airway. Similarly, the Ca2+ oscillations varied in different generations of the same airway, with a slower frequency in the SMCs of the distal zone as compared with the middle or proximal zones of airways. By contrast, high KCl induced minimal contraction and very slow Ca2+ oscillations throughout the whole intrapulmonary airway. The slower agonist-induced Ca2+ oscillations in the distal zone correlated with a reduced expression of agonist receptors. The layer of SMCs increased in thickness in the middle and proximal zones. These results indicate that the contractility of airway SMCs varies at different positions along the same airway and that this response partially results from different Ca2+ signaling and the total amount of the SMCs.
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