NITRIC OXIDE (NO) INHIBITS [Ca2+]i RESPONSE TO ACETYLCHOLINE BY REGULATING SECOND MESSENGER PRODUCTION IN AIRWAY SMOOTH MUSCLE. † 1802

Abstract

NO inhibits acetylcholine (ACh)-induced intracellular Ca2+([Ca2+]i) oscillations in b-escin permeabilized porcine tracheal smooth muscle (TSM) cells. Using real-time confocal microscopy and radioimmunoassay, we determined the mechanisms by which NO inhibits the [Ca2+]i response to ACh. Heparin, a selective IP3 receptor antagonist, and U73122, a phospholipase C inhibitor, slowed the frequency of ongoing ACh-induced oscillations. Pre-exposure to U73122 or heparin prevented the initiation of ACh-induced [Ca2+]i oscillations. The [Ca2+]i response to ACh was abolished by ruthenium red, a ryanodine receptor (RyR) antagonist, and by 8-amino-cyclic ADP-ribose, an antagonist of cyclic ADP-ribose (cADPR) receptor. The [Ca2+]i response to ACh, IP3 and cADPR were abolished by s-nitroso-n-acetylpenicillamine (SNAP), a NO donor. SNAP reduced ACh-induced elevation of IP3 and cADPR levels. These results indicate that ACh-induced [Ca2+]i oscillations involve Ca2+ release by IP3 and cADPR and NO regulates their production. Supported by Graduate School, Univ. of Minnesota, NIH grant HL51736 and Abbott Laboratories.