OXYGEN RADICALS IN EXSANGUINATION-INDUCED BRONCHOCONSTRICTION OF GUINEA-PIGS

This study investigated the relationship between oxygen radicals and e xsanguination-induced bronchoconstriction using antioxidant in guinea pigs. To accomplish this, two phases of studies were carried out. In p hase I, 34 guinea pigs weighing 342 +/- 11 g were divided into five gr oups: control (n = 7); acute dimethylthiourea (DMTU, n = 7); chronic D MTU (n = 8); superoxide dismutase (SOD, n = 6); and catalase (n = 6). Animals in the control group were not treated. DMTU, SOD, and catalase were employed for the scavenging of hydroxyl radical, superoxide anio n, and hydrogen peroxide, respectively. Ten additional guinea pigs wei ghing 293 +/- 6 g were divided into two groups in phase 2: sham (n = 6 ) and chronic apocynin (n = 4). Animals in the sham group received inj ections of the vehicle, whereas apocynin was used to suppress the prod uction of superoxide anion. All animals were anesthetized, sternotomiz ed, and artificially ventilated. Before (baseline) as well as at fixed intervals 5-30 minutes following the exsanguination, the maximal expi ratory flow maneuver was performed and the dynamic compliance (Cdyn) w as obtained. Decreases in the maximal expiratory flow at 50% baseline vital capacity and Cdyn were used as indicators of bronchoconstriction . Exsanguination in the control and sham groups caused a gradual incre ase in airway constriction with time that was significantly ameliorate d by chronic DMTU and chronic apocynin pretreatments but was not affec ted by other acute treatments. These results indicate that chronic tre atment with antioxidants ameliorates exsanguination-induced, tachykini n-mediated airway constriction.