Fig. 4.
Effect of ANG II on reactive oxygen species (ROS) levels in the carotid body. Malondialdehyde (MDA) levels were analyzed in carotid body extracts as an index of ROS. Top: protocols for MDA analysis with repetitive and continuous applications of ANG II. Analysis of MDA at the end of 60-min superfusion without ANG II served as controls. A: carotid bodies were challenged with repetitive application of 60 pM ANG II (5 times for 30 s each at 5-min intervals), and MDA levels were determined at minute 60 of the poststimulation period. Protocols were repeated in the presence of 3 μM losartan, an angiotensin type 1 (AT1) receptor antagonist, or 500 μM apocynin, an inhibitor of NADPH oxidase 2 (Nox2). B: effect of continuous application of 60 pM ANG II for 150 s on MDA levels in the carotid body. MDA levels were determined at 5 min (ANG II ×1, 5 min) or 60 min (ANG II ×1, 60 min). MDA levels were elevated when measured at 5 min, but not 60 min, after termination of continuous application of ANG II and losartan (3 μM) or apocynin (500 μM) blocked this effect. Values are means ± SE from 4 individual experiments performed in triplicate. ***P < 0.001. NS, P > 0.05 compared with vehicle-treated controls.