Oxygen radicals in exsanguination-induced bronchoconstriction of guinea pigs

This study investigated the relationship between oxygen radicals and exsanguination-induced bronchoconstriction using antioxidant in guinea pigs. To accomplish this, two phases of studies were carried out. In phase 1, 34 guinea pigs weighing 342 +/- 11 g were divided into five groups: control (n = 7); acute dimethylthiourea (DMTU, n = 7); chronic DMTU (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 anion, and hydrogen peroxide, respectively. Ten additional guinea pigs weighing 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 injections of the vehicle, whereas apocynin was used to suppress the production of superoxide anion. All animals were anesthetized, sternotomized, and artificially ventilated. Before (baseline) as well as at fixed intervals 5-30 minutes following the exsanguination, the maximal expiratory flow maneuver was performed and the dynamic compliance (Cdyn) was 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 increase in airway constriction with time that was significantly ameliorated by chronic DMTU and chronic apocynin pretreatments but was not affected by other acute treatments. These results indicate that chronic treatment with antioxidants ameliorates exsanguination-induced, tachykinin-mediated airway constriction.