Acute Antioxidant (AOX) Treatment Increases Muscle Microvascular O 2 Extraction in Young Rats

AOX treatment (76 mg/kg vitamin C, 52 mg/kg tempol) elevates microvascular O 2 pressures (PO 2 mv ) at rest and following the onset of muscle contractions in aged (A) rats reducing fractional O 2 extraction (Herspring et al. J. Appl. Physiol. 2008). PURPOSE To test the hypothesis that this specific AOX treatment would elevate PO 2 mv in the spinotrapezius muscle of young (Y) rats at rest and during contractions. METHODS PO 2 mv , which reflects the dynamic balance between O 2 delivery/utilization (fractional O 2 extraction), was measured via phosphorescence quenching in the spinotrapezius of 12 Y (6‐8 mo) and 15 A (26‐30 mo) Fisher 344 x BN rats. Electrically‐induced contraction bouts (1 Hz twitch) were performed with and without (CON) intra‐arterial AOX administration. The PO 2 mv response was fitted with an exponential model and compared using two‐way ANOVA (age x condition). RESULTS The CON baseline PO 2 mv was not different (P>0.05) between Y (31±4 mmHg) and A (30±3 mmHg). However, AOX decreased baseline PO 2 mv in Y (25±5 mmHg) whilst it was increased in A (36±3 mmHg) (both P<0.05). Moreover, throughout contractions in Y, AOX decreased PO 2 mv below CON values by 21 + 6% on average (P<0.05). CONCLUSIONS The impact of AOX supplementation on PO 2 mv is age‐dependent. In contrast to A rats, in Y rats, AOX reduced PO 2 mv (increased fractional O 2 extraction) at rest and during contractions. Support: AHA, Heartland Affiliate 0750090Z