Shaf Keshavjee. KCl evokes contraction of airway smooth muscle

10.1152/ajplung.00130.2004.—Airway smooth muscle (ASM) cells ex-press voltage-dependent Ca2 channels, primarily of the L-subtype. These may play a role in excitation-contraction coupling of ASM, although other signaling pathways may also contribute: one of these includes Rho and its downstream effector molecule Rho-associated kinase (ROCK). Although voltage-dependent Ca2 influx and Rho/ ROCK signaling have traditionally been viewed as entirely separate pathways, recent evidence in vascular smooth muscle suggest differently. In this study, we monitored contractile activity (muscle baths) in bron-chial and/or tracheal preparations from the pig, cow, and human, and further examined Rho and ROCK activities (Western blots and kinase assays) and cytosolic levels of Ca2 (fluo 4-based fluorimetry) in porcine tracheal myocytes. KCl evoked substantial contractions that were sup-pressed in tracheal preparations by removal of external Ca2 or using the selective L-type Ca2 channel blocker nifedipine; porcine bronchia