Changes in reactivity of rat arteries subjected to dynamic stretch

The effect of dynamic stretch on the reactivity of the rat tail and mesenteric artery segments was studied. Segments mounted on a myograph were stretched by a computer-controlled motorized micromanipulator. Dynamic stretch (1, 5 or 7 Hz) inhibited the artery constriction induced by noradrenaline (10 microM), 5-hydroxytryptamine (0.7 microM), or electrical field stimulation of intramural nerves. In contrast, dynamic stretch enhanced the tetrodotoxin-insensitive dilation induced by electrical field stimulation of noradrenaline-contracted arteries. Maximal increase of dilation evoked by electrical field stimulation (24.5 +/- 5.0% in mesenteric and 50.3 +/- 15.6% in the tail artery) was observed at a dynamic stretch-frequency of 5 Hz. An inhibitor of nitric oxide synthesis, NG-nitro-L-arginine (100 microM), abolished the difference in reactivity between static and dynamic conditions. The results indicate that dynamic stretch of the arteries activates nitric oxide synthesis/secretion, thus reducing constrictor and increasing dilator responses to the stimuli used.