Comparison between the effects of Captopril and Lisinopril on Bradykinin-induced contraction in tracheal smooth muscle of guinea pig

Background: ace inhibitors are used for the treatment of hypertension and congestive heart disease may induce hyper-reactivity of the airways which may be associated with the accumulation of bradykinin and other inflammatory mediators present in the airways. aim: to compare the effect of captopril with lisinopril on bradykinin-induced tracheal smooth muscle contraction of guinea pig trachea. methods: a comparative controlled in-vitro experimental study was carried out on the tracheal smooth muscle strips of guinea pig pretreated with indomethacin (10-6m),phentolamine (10-5m) and propranalol (10-6 m) to remove the effect of endogenous catecholamin and prostaglandins. the activity of trachealis smooth muscle was noted through the isometric force displacement transducer on a four channel oscillograph. cumulative concentration-response relationship was displayed by adding successive concentrations of bradykinin on the tracheal strips starting with 22μg to 132 μg/dl. results: bradykinin produced concentration dependent reversible contraction of isolated tracheal smooth muscle. the mean value of response achieved with 132 μg/dl of bradykinin in the presence of captopril was 51.33±2.79 and in the presence of lisinopril was 38.17±2.94. these ace inhibitors shifted the concentration response curves of bradykinin to left and upward. on comparison among themselves it was observed that lisinopril as compared to captopril produced less enhancement of bradykinin-induced contraction of guinea pig tracheal smooth muscle. conclusion: lisinopril produce less enhancement of bradykinin induced tracheal smooth muscle contraction then captopril. © 2016,lahore medical and dental college. all rights reserved.