Acute antioxidant therapy restores baroreflex sensitivity in spontaneously hypertensive rats

Abstract

During hypertension there is impairment in baroreflex sensitivity (BRS). Here we tested the hypothesis that acute superoxide scavenging would restore the depressed BRS in spontaneously hypertensive rats (SHR). Serum samples from SHR (n=20) and WKY (n=20) were subjected to TBARS assay before and after the administration of tiron (30 mg/Kg, i.v.), a superoxide dismutase mimetic, or apocynin (30 mg/Kg), a NADPH oxidase inhibitor. Cardiovascular parameters were recorded in male 10‐week‐old SHR (n=14) and their controls (WKY, n=14). In addition, BRS was tested using phenylephrine (8 mg/Kg, i.v.) and sodium nitroprusside (25 μg/Kg, i.v.) before and after tiron or apocynin administration. The SHR group had considered oxidative stress compared to WKY (36.2±3.0 vs. 13.3±2.6 nmol/L), SHR + APO group showed a reduction in oxidative stress when compared to SHR (36.2±3.0 vs. 21.5±3.0 nmol/L) so was the SHR + Tiron (37.2±3.9 vs. 21.9±1.6 nmol/L). Regarding BRS, SHR presented diminished BRS when compared to WKY (−1.34±0.11 vs. −2.91±0.20 bpm.mmHg−1). Acute administration of tiron improved BRS in SHR (−2.26±0.21 vs. −1.34±0.11 bpm.mmHg−1). Furthermore, acute apocynin improved BRS in SHR (−2.14±0.23 vs. −1.34±0.11 bpm.mmHg−1). Both tiron and apocynin had no effect on BRS in WKY. These data suggest that acute scavenging of NADPH oxidase‐derived superoxide improves baroreflex sensitivity in SHR.