l -Arginine Treatment Alters the Kinetics of Nitric Oxide and Superoxide Release and Reduces Ischemia/Reperfusion Injury in Skeletal Muscle

Abstract

Background Constitutive nitric oxide synthase (cNOS) may produce species involved in ischemia/reperfusion (I/R) injury: NO in the presence of sufficient l -arginine and superoxide at the diminished local l -arginine concentration accompanying I/R. Methods and Results During hindlimb I/R (2.5 hours/2 hours), in vivo NO was continuously monitored (porphyrinic sensor), and l -arginine (chromatography), superoxide (chemiluminescence), and I/R injury were measured intermittently. Normal rabbits were compared with those infused with l -arginine 4 mg·kg −1 ·min −1 for 1 hour. In both groups, ≈6 minutes into ischemia, a rapid increase of NO from its basal level of 50±17 to 115±7 nmol/L, P <.005 (microvessels), was observed. In animals not treated with l -arginine, NO dropped below basal to undetectable levels (<1 nmol/L) during reperfusion. In animals treated with l -arginine, the decrease of NO was slower, such that substantial amounts accumulated during reperfusion (25 nmol/L). Decreased NO during I/R was accompanied by increased superoxide, which during reperfusion reached 50 nmol/L without or 23 nmol/L with l -arginine treatment. Calcium-dependent cNOS was a major source of superoxide release (inhibited 70% by L-NMMA and 25% by L-NAME) during I/R. Conclusions l -Arginine treatment decreased superoxide generation by cNOS while increasing NO accumulation, leading to protection from constriction (microvessel area, 17.77±0.95 versus 11.66±2.21 μm 2 untreated, P <.0005) and reduction of edema after reperfusion (interfiber area, 16.56±2.13% versus 27.68±7.70% untreated, P <.005).