Pulsatile stretch in coronary arteries elicits release of endothelium-derived hyperpolarizing factor - A modulator of arterial compliance

To date, the release of the endothelium-derived hyperpolarizing factor (EDHF) has been demonstrated only in response to receptor-dependent Ca2+-elevating agonists. Since endothelial cells in situ are continuously subjected to rhythmic distension, we investigated the effect of rhythmic stretch on the release of EDHF from isolated porcine coronary arteries. In the combined presence of diclofenac and N-G-nitro-L-arginine (L-NNA), sinusoidal pressure oscillations (from 40 to 50 mm Hg, 4 minutes, 1.5 Hz) led to simultaneous oscillations in the external diameter of coronary artery segments, the amplitude of which were decreased by iberiotoxin and apamin and also by endothelial denudation, In order to directly demonstrate the release of EDHF, the intraluminal solution from endothelium-intact coronary segments exposed to pulsatile stretch was applied to detector rat aortic smooth muscle cells, the membrane potential of which was continuously measured using the patch-clamp technique. The hyperpolarization of detector cells induced by the intraluminal solution was proportional to the amplitude of the pressure oscillations applied to the donor artery and was attenuated by either preincubation of donor arteries with 17-octadecynoic acid or application of either tetrabutylammonium or iberiotoxin to detector cells. In contrast to the bradykinin-induced release of EDHF, the EDHF synthesized in response to pulsatile stretch did not exhibit any tachyphylaxis. These findings demonstrate for the first time that the synthesis of EDHF in coronary arteries can be mechanically stimulated by rhythmic vessel wall distension and suggest that the continuous release of EDHF may contribute to the adjustment of an adequate vascular compliance and to the control of coronary blood flow.