Alteration of Endothelium-Dependent Hyperpolarizations in Porcine Coronary Arteries With Regenerated Endothelium

Abstract

The present study was designed to test the ability of regenerated endothelium to evoke endothelium-dependent hyperpolarizations. Hyperpolarizations induced by serotonin and bradykinin were compared in isolated porcine coronary arteries with native or regenerated endothelium, 4 weeks after balloon endothelial denudation. The experiments were performed in the presence of inhibitors of nitric oxide synthase (Nomega-nitro-L-arginine) and cyclooxygenase (indomethacin). The transmembrane potential was measured using conventional glass microelectrodes. Smooth muscle cells from coronary arteries with regenerated endothelium were depolarized in comparison with control coronary arteries from the same hearts. Spontaneous membrane potential oscillations of small amplitude or spikes were observed in some of these arteries but never in arteries with native endothelium. In coronary arteries from control pigs, both serotonin and bradykinin induced concentration-dependent hyperpolarizations. In the presence of ketanserin, 10 micromol/L serotonin induced a transient hyperpolarization in control coronary arteries. Four weeks after balloon denudation, the response to serotonin was normal in arteries with native endothelium, but the hyperpolarization was significantly lower in coronary arteries with regenerated endothelium. In control arteries, the endothelium-dependent hyperpolarization obtained with bradykinin (30 nmol/L) was reproducible. Four weeks after balloon denudation, comparable hyperpolarizations were obtained in coronary arteries with native endothelium. By contrast, in arteries with regenerated endothelium, the hyperpolarization to bradykinin became voltage-dependent. In the most depolarized cells, the hyperpolarization to bradykinin was augmented. The changes in resting membrane potential and the alteration in endothelium-dependent hyperpolarizations observed in the coronary arteries with regenerated endothelium may contribute to the reduced response to serotonin and the unchanged relaxation to bradykinin described previously.

Phenotypic and Functional Changes in Regenerated Porcine Coronary Endothelial Cells

“…Contrary to the relaxations induced by both bradykinin and the calcium ionophore for which the decreased production of NO can be compensated by the release of endothelium-derived hyperpolarizing factor, 34,35 serotonin exclusively stimulated NO production and so fails to induce relaxation of coronary arteries with regenerated endothelium. The present findings permit us to propose an explanation for the endothelial dysfunction in which the pertussis toxin-sensitive G protein pathway is altered first.…”

Stimulation of Bradykinin B 1 Receptors Induces Vasodilation in Conductance and Resistance Coronary Vessels in Conscious Dogs

“…21 This CBFv response to bradykinin, which is resistant to inhibitors of NO synthase, may be mediated by endothelium-derived hyperpolarizing factor (EDHF), because it has been shown that the relaxing response of coronary vessels to bradykinin is also mediated by EDHF, which probably acts through calcium-activated potassium channels. 22,23 However, the in vivo role of EDHF remains unknown because EDHF has not been identified. The coronary effects of des-Arg 9 -bradykinin on conductance and resistance vessels were prevented by LNA, indicating that the effects of des-Arg 9 -bradykinin are, in a large part, mediated by NO, which is consistent with a previous study in which NO synthase inhibitors and des-Arg 9 -bradykinin were administrated intravenously.…”

Neuronal NOS-dependent dilation to flow in coronary arteries of male eNOS-KO mice

“…Also, this depolarization is unlikely to be due to the absence of endothelial NO per se, because in both eNOS-KO and WT mice, treatment of the arteries with either L-NNA or Indo or endothelial removal did not affect the resting membrane potential, indicating that basal release of NO or prostaglandins does not modulate membrane potential and/or myogenic tone of vascular smooth muscle of these mice (1,27,31). It has been demonstrated that eNOS-KO mice are hypertensive (27); a condition characterized by depolarization of the arterial smooth muscle cells and enhanced myogenic tone with endothelial dysfunction (4,10,34). In this context, the enhanced basal tone resulting from depolarization of smooth muscle cells observed in eNOS-KO coronary arteries may be linked to the physical effect of high pressure on the vessel wall or the vascular remodeling in response to the lack of NO.…”