ROLE OF NITRIC OXIDE IN GOVERNING BLOOD FLOW DYNAMICS TO CHANGES IN WORK INTENSITY.

Abstract

Previous studies have shown that nitric oxide (NO) can contribute to the dynamics of blood flow regulation in the transition from rest to exercise and in recovery from exercise. PURPOSE We sought to determine whether NO governs the dynamic characteristics by which blood flow adjusts to changes in work intensity (treadmill grade) during exercise. METHODS The following studies were carried out on seven Sprague-Dawley rats before and after NO synthase inhibition by 10 mg/kg L-NAME. While the rats walked on a treadmill at 10 m/min, treadmill incline was elevated from −10° to +10° in a step. Treadmill incline was also varied in a sinusoid between −10° to +10° at 0.01, 0.02, 0.04 0.06, and 0.10 Hz. RESULTS The delay to the onset of vasodilation in response to the step increase in grade averaged 5.0±1.8 s and 7.0±2.4 s before and after L-NAME, respectively (p = 0.16). From the low to the high frequency during sinusoidal exercise, the delays ranged from 8.6±1.2 s to 3.8±0.2 s in the control condition, and from 8.5±1.2 s to 3.6±0.3 s following L-NAME (p = 0.11 control vs. L-NAME). CONCLUSION NO does not contribute to the dynamics of blood flow regulation when treadmill incline is changed during constant speed locomotion in rats. Supported by NIH Grant RO1 HL46314.