Role of guanylate cyclase and arachidonic acid metabolites in the regulation of epithelium-dependent relaxation of tracheal smooth muscles in rats

Abstract

The effects of guanylate cyclase modulators and inhibitors of the arachidonic acid metabolism on epithelium-dependent smooth muscle reactions of rat tracheal segments were studied by a mechanographic technique. Application of phenylephrine to the tracheal segments precontracted by high-potassium Krebs' solution reduced their mechanical tension. This reaction was considerably less pronounced in the tracheal segments from which the epithelium had been removed. Phenylephrine-induced relaxation was suppressed by preincubation with methylene blue, but was not affected by preincubation with either indomethacin (a cyclooxygenase inhibitor) or nordihydroguaiaretic acid (a lipoxygenase inhibitor). These data suggest that the epithelium-dependent relaxation of the tracheal smooth muscle is mediated by guanylate cyclase activation, and arachidonic acid metabolites do not significantly contribute to this reaction.