In vivo analysis of skin microcirculation and the role of nitric oxide during vibration.

Studies in healthy volunteers and patients with renal failure have shown that vibration, applied with a frequency of 47 Hz and a vibrational intensity of 600 mVpp, increases microcirculation of blood in the skin. This controlled, in vivo, experimental study was conducted to further evaluate the effect of vibration on skin microcirculation and to ascertain whether administration of a nitric oxide (NO) synthase inhibitor (NG-nitro-L-arginine methyl ester [L-NAME]) diminishes the effect of vibration on skin blood flow. Using a mouse microcirculatory model, 12 animals were prepared for study (six in the control and six in the experimental group). In the experimental group, vibrations were applied horizontally for 15 minutes. The control group received no vibration. Venular blood flow was measured using intravital videomicroscopy at baseline and at 0, 5, and 15 minutes after the application of vibration. Vibration significantly increased the blood flow at 5 and 15 minutes after application (P = 0.002 and P = 0.046, respectively). Differences between the control and experimental group also were statistically significant (P = 0.0017 and P = 0.046, respectively). In the second study, all animals (seven in each group) received an intraperitoneal injection of NO synthase inhibitor L-NAME before vibration application. When NO synthase inhibitor L-NAME was administered, the increase in blood flow in the vibration group was minimal after 5 and 10 minutes, and nonexistent after 15 minutes. No significant differences between the control and experimental group were observed. Because NO synthase inhibitor L-NAME inhibits NO production in vivo, these findings imply the involvement of NO in the observed blood flow increase during vibration. Future clinical trials to establish evidence as to the beneficial effects of vibration are warranted.