Effects of the selective muscarinic receptor antagonist penehyclidine hydrochloride on the respiratory tract.

We investigated the effects and mechanisms of penehyclidine hydrochloride (PHC), a novel selective anticholinergic drug on respiratory tract. The methods of isolated guinea-pig tracheas, and isolated bronchoalveoar lavage fluid were employed to estimate PHC's anti-spasm mechanisms in smooth muscle. The results indicated relaxing effect of penehyclidine hydrochloride was obviously stronger than that of atropine sulfate in two assays according to PA2 values and maximal reducing mount index. The method of radio-immunity assay was furtherly employed to determine cAMP levels in isolated guinea-pig tracheal and lung smooth muscle for comparing with selective effect on muscarinic receptor subtypes. In the assay, PHC could increase the content of cAMP in isolated guinea-pig lung smooth muscle, while decrease the content of cAMP in isolated guinea-pig tracheal smooth muscle, but the difference was no statistical significant at dose of 10 micromol x L(-1). In conclusion, our results suggested that PHC has little or no effect on M2 receptor subtypes in isolated guinea-pig tracheal and lung smooth muscle and could be used in asthma and COPD therapy.