Vibration-Induced Inhibition of Vascular Smooth Muscle Contraction

Abstract

Vascular smooth muscle is known to be exposed to an oscillating strain under physiological and pathophysiological conditions as well as in different occupational and environmental situations. The effect of vibrations on smooth muscle seems to be largely unknown. In the present experiments on isolated preparations of the rat portal vein and the rabbit thoracic aorta, imposed sinusoidal changes in length were found to cause prompt reduction in active force, the extent of which was dependent on amplitude (1–10% of tissue length, peak to peak, i.e. approximately ± 50–500 µm) and frequency of vibration (1–400 Hz) as well as on the prevailing level of active and passive forces. Vibrations caused only small and inconsistant reductions of passive force of the vascular smooth muscle. The results are in accordance with the hypothesis that vibrations exert a direct action on the contractile process by causing an increased rate of detachment of actin-myosin cross-links. It is suggested that, in vivo, vibrations may affect the diameter of conduit arteries locally in the case of turbulent blood flow as seen in post-stenotic dilatation and arterio-venous anastomosis. Possibly, even the normal pulse pressure oscillations may sometimes tend to inhibit the smooth muscle activity in such arteries and thereby influence their diameters.