NADH/NADPH oxidase and enhanced superoxide production in the mineralocorticoid hypertensive rat

We previously reported increased aortic reactive oxygen species (ROS) produ ction in mineralocorticoid (deoxycorticosterone acetate [DOCA]-salt) hypert ensive rats. In the present study, we tested the hypothesis that NADH/NADPH oxidase is responsible for increased ROS production, namely superoxide (O- 2(-)), in aorta from the DOCA-salt rat. Treatment of aortic rings from DOCA -salt rats with the NO synthase inhibitor N-nitro-L-arginine and the xanthi ne oxidase inhibitor allopurinol did not significantly change O-2(-) produc tion. Furthermore, de-endothelialization of aorta from DOCA-salt rats did n ot affect O-2(-) production compared with that of sham-operated rats. Thus, xanthine oxidase and uncoupled endothelial NO synthase were not responsibl e for increased O-2(-) production in the DOCA-salt rats. In contrast, treat ment with the NADPH oxidase inhibitor apocynin significantly decreased O-2( -) production in aortic rings from DOCA-salt rats compared with sham-operat ed rats. Moreover, long-term administration of apocynin (in drinking water, 1.5 mmol/L, 28 days) to DOCA-salt rats significantly decreased systolic bl ood pressure compared with that of rats treated with DOCA-salt alone. Furth ermore, O-2(-) production in aortic rings from DOCA-salt rats treated with apocynin for 28 days was reduced compared with that of untreated DOCA-salt rats. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis dem onstrated that DOCA-salt rats have significantly greater mRNA levels of the NADPH oxidase subunit p22phox than do sham-operated rats. These findings s uggest that NADPH oxidase is increased and is responsible for increased O-2 (-) production and possibly contributes to increased blood pressure in the DOCA-salt hypertensive rat.