An endothelium-derived hyperpolarizing factor distinct from NO and prostacyclin is a major endothelium-dependent vasodilator in resistance vessels of wild-type and endothelial NO synthase knockout mice

Abstract

In addition to nitric oxide (NO) and prostacyclin (PGI2), the endothelium generates the endothelium-derived hyperpolarizing factor (EDHF). We set out to determine whether an EDHF-like response can be detected in wild-type (WT) and endothelial NO synthase knockout mice (eNOS ؊͞؊) mice. Vasodilator responses to endothelium-dependent agonists were determined in vivo and in vitro. In vivo, bradykinin induced a pronounced, dose-dependent decrease in mean arterial pressure (MAP) which did not differ between WT and eNOS ؊͞؊ mice and was unaffected by treatment with N -nitro-L-arginine methyl ester and diclofenac. In the salineperfused hindlimb of WT and eNOS ؊͞؊ mice, marked N -nitro-L-arginine (L-NA, 300 mol͞liter)-and diclofenac-insensitive vasodilations in response to both bradykinin and acetylcholine (ACh) were observed, which were more pronounced than the agonistinduced vasodilation in the hindlimb of WT in the absence of L-NA. This endothelium-dependent, NO͞PGI2-independent vasodilatation was sensitive to KCl (40 mM) and to the combination of apamin and charybdotoxin. Gap junction inhibitors (18␣-glycyrrhetinic acid, octanol, heptanol) and CB-1 cannabinoid-receptor agonists (⌬ 9 -tetrahydrocannabinol, HU210) impaired EDHF-mediated vasodilation, whereas inhibition of cytochrome P450 enzymes, soluble guanylyl cyclase, or adenosine receptors had no effect on EDHFmediated responses. These results demonstrate that in murine resistance vessels the predominant agonist-induced endotheliumdependent vasodilation in vivo and in vitro is not mediated by NO, PGI 2 , or a cytochrome P450 metabolite, but by an EDHF-like principle that requires functional gap junctions. T he endothelium plays an important role in the control of vascular tone. At least three different vasodilating agents are synthesized by the endothelium upon exposure to mechanical forces, such as shear stress, or to receptor-dependent agonists, such as acetylcholine (ACh) and bradykinin. Whereas the properties of two of these vasodilators, nitric oxide (NO) and prostacyclin (PGI 2 ), have been extensively investigated, the nature and mechanism of action of the third vasodilator, the endothelium-derived hyperpolarizing factor (EDHF), is still controversial (1-7).The purpose of the present study was to characterize EDHFmediated responses in vivo, in isolated arteries, and in the perfused hindlimb of the mouse. To address the hypothesis that NO might be EDHF, we also determined endotheliumdependent relaxation in endothelial NO synthase (eNOS) knockout (eNOS Ϫ͞Ϫ) mice. Materials and MethodsMice. Homozygous eNOS Ϫ͞Ϫ mice were obtained from the colonies at Heinrich-Heine-Universität, Düsseldorf (genetic background C57BL͞b6) and Beth Israel

Lack of vascular connexin 40 is associated with hypertension and irregular arteriolar vasomotion

“…Moreover, the efficacy of NO as well as ACh in reducing pressure were similar in both wild-type and Cx40 Ϫ/Ϫ mice, suggesting that the dilator potency of enhanced levels of NO is also not affected by the loss of Cx40. Recently, it has been proposed that dilations induced by ACh in mice involve a mechanism that is distinct from NO and prostaglandins (2). Also in the present study, systemic blockade of NO synthase did not affect the maximal amplitude, but only the duration of ACh-induced pressure drops, suggesting that other endothelial dilator mechanisms, namely endothelium-derived hyperpolarizing factor (EDHF), are important.…”

“…avi) and is also available as Supplementary Material at the Physiological Genomics web site]. 2 When observed in an arteriole, these constrictions could be abrogated by the superfusion of ACh or SNP but returned upon removal of the dilator substance. In contrast to this irregular behavior, normal vasomotion is characterized by simultaneous diameter changes along the entire vessel length and can be observed in wildtype and Cx40-deficient mice (Fig.…”

Chronic clofibrate administration prevents salineinduced endothelial dysfunction and oxidative stress in young Sprague-Dawley rats

“…8 EDHF is a non-NO, non-prostanoid endothelium-derived hyperpolarizing factor that persists after effective inhibition of nitric oxide synthase and cyclo-oxygenase pathways. 9,10 EDHF dependent vasorelaxation is mediated through calcium-activated potassium channels (KCa). 11 Several substances may comprise EDHF, including epoxyeicosatrienoic acid (EET), anandamide, hydrogen peroxide, and potassium ion.…”

Selective Stimulation of VEGFR2 Accelerates Progressive Renal Disease

“…16,32 In contrast, the present study documented that overexpression of Flk-sel reduced systemic BP, despite eNOS deficiency. This suggests that alternative factors that contribute to BP regulation, including endothelial-derived hyperpolarizing factor, [47][48][49][50] could be altered by Flk-sel.…”