L-NMMA reduced skeletal muscle blood flow at rest (8.7 vs 14.0 ml/min/100g) and during exercise compared to control, whereas L-arginine increased blood flow only at rest (20.5 vs 14.0 ml/min/100g).
Does nitric oxide modulation with L-NMMA or L-arginine alter skeletal muscle blood flow at rest and during dynamic exercise in physically active men?
Nitric oxide plays a significant role in regulating skeletal muscle blood flow both at rest and during dynamic exercise in humans.
The role of nitric oxide at rest and in the active hyperemic response within skeletal muscle was investigated in eight physically active men. Three microdialysis probes were inserted into the vastus lateralis of the quadriceps femoris muscle group in each subject. Microdialysis probes were perfused with a Ringer solution containing 5.0 mM ethanol, 2.5 mM glucose, and either 10 mg/ml of the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) monoacetate salt, 30 mg/ml of the nitric oxide precursor L-arginine, or no additional substance (control probe). Subjects performed one-legged cycling exercise at work rates ranging from 25 to 100 W. Dialysate and perfusate ethanol concentrations were presented as the ratio of ethanoldialysate to ethanolperfusate (ethanol outflow-to-inflow ratio), an indicator that is inversely related to blood flow. The ethanol outflow-to-inflow ratios at rest were 0.614 +/- 0.032, 0.523 +/- 0.023, and 0.578 +/- 0.039 in the L-NMMA, L-arginine, and control probes, respectively. Calculated resting blood flows were therefore 8.7 +/- 4.1, 20.5 +/- 4.6, and 14.0 +/- 4.7 ml.min-1.100 g-1 around the L-NMMA, L-arginine, and control probes, respectively. The ethanol outflow-to-inflow ratios were significantly higher at all exercise intensities in the L-NMMA probe than in the control and L-arginine probes, resulting in calculated blood flows of 195 +/- 55, 407 +/- 47, and 352 +/- 60 ml.min-1.100 g-1 at 25 W and 268 +/- 65, 602 +/- 129, and 519 +/- 113 ml.min-1.100 g-1 at 100 W around the L-NMMA, L-arginine, and control probes, respectively. Skeletal muscle blood flow was therefore reduced both at rest and during continuous, dynamic exercise by the action of L-NMMA, whereas blood flow was increased only at rest by L-arginine.
Hickner et al. (Tue,) conducted a other in Healthy physically active men (n=8). L-NMMA and L-arginine vs. Control (no additional substance) was evaluated on Skeletal muscle blood flow at rest and during dynamic exercise. L-NMMA reduced skeletal muscle blood flow at rest (8.7 vs 14.0 ml/min/100g) and during exercise compared to control, whereas L-arginine increased blood flow only at rest (20.5 vs 14.0 ml/min/100g).