Original Article Contraction Stimulates Nitric Oxide–Independent Microvascular Recruitment and Increases Muscle Insulin

We examined whether contraction-induced muscle microvas-cular recruitment would expand the surface area for insulin and nutrient exchange and thereby contribute to insulin-mediated glucose disposal. We measured in vivo rat hindlimb microvascular blood volume (MBV) using contrast ultra-sound and femoral blood flow (FBF) using Doppler ultra-sound in response to a stimulation frequency range. Ten minutes of 0.1-Hz isometric contraction more than doubled MBV (P< 0.05; n 6) without affecting FBF (n 7), whereas frequencies>0.5 Hz increased both. Specific inhibition of nitric oxide (NO) synthase with N-L-nitro-arginine-methyl ester (n 5) significantly elevated mean arterial pressure by 30 mmHg but had no effect on basal FBF or MBV. We next examinedwhether selectively elevatingMBVwithout increas-ing FBF (0.1-Hz contractions) increased muscle uptake o