Rat Mesenteric Arterial Bed Research Articles

The Hypotensive and Vasodilatory Effects Observed in Rats Exposed to Chiranthodendron pentadactylon Larreat Flowers Can Be Attributed to Cyanidin 3-O-Glucoside

Chiranthodendron pentadactylon Larreat is a tree native to southeastern Mexico and Guatemala. Its flower is used in Mexican folk medicine to treat a variety of diseases, including conditions of blood pressure. However, scientific information on its usefulness in this pathology is lacking. The present study evaluates the effect of a methanolic extract (ME) from the flower and its active constituents on heart rate (HR) and mean arterial pressure (MAP) in anesthetized rats (MAPHR). The study also analyzed the effects on rat-isolated aortic rings (RIAR) and the rat mesenteric arterial bed (MABR). Active fractions were chromatographed, which led to the isolation of cyanidin 3-O-glucoside (C3G) identified through HPLC. The Chiranthodendron pentadactylon flowers produced hypotensive and vasorelaxant effects associated with C3G. The vasorelaxant effect is a mechanism underlying the synthesis and release of nitric oxide (NO). Neither cholinergic receptors nor prostaglandins are involved. ME and C3G cause cardiovascular depression in anesthetized rats via cholinergic and prostanoid mechanisms. Our research expands the scientific understanding of the flowers on the rat cardiovascular system. This amplifies the appreciation of the flower’s ethnomedicine employed to control blood pressure. However, researchers need to conduct toxicity studies to determine the safety of this plant.

Vasorelaxant Effect of Moroccan Cannabis sativa Threshing Residues on Rat Mesenteric Arterial Bed is Endothelium and Muscarinic Receptors Dependent.

Ethanolic fraction of Moroccan Cannabis sativa threshing residues (EFCS) was evaluated for its vasorelaxant activity. The current work aims to identify the active metabolites in the ethanolic fraction of the EFCS and illustrate their mechanism of action. Free radical scavenging capacity of EFCS was assessed using DPPH method. The EFCS vasodilation activities in phenylephrine-precontracted isolated rat mesenteric arterial beds were investigated in presence of L-NAME (nitric oxide synthase inhibitor), indomethacin (cyclooxygenase inhibitor), potassium channel blockers (namely tetraetylamonium, barium chloride, and glibenclamide), and atropine. Nitric oxide vascular release was measured by electron paramagnetic resonance (EPR) using a spin trap in rat aortic rings. EFCS induced dose-dependent vasorelaxation on mesenteric vascular bed. Incubation of the preparations with L-NAME, ODQ (a soluble guanylyl cyclase inhibitor), or potassium channel blockers reduced the fall of perfusion pressure caused by EFCS. Endothelial denudation or atropine abolished the EFCS's vasorelaxant effect, suggesting involvement of muscarinic receptors and endothelium-relaxing factors. The extract induced nitric oxide release in aortic rings in a similar manner as acetylcholine suggesting an effect of EFCS on the muscarinic receptor and the conductance arteries. Chemical investigation of EFCS identified potential active components namely apigenin and derivatives of luteolin skeleton and also additional components such as neophytadiene, squalene, and β-sitosterol. In conclusion, the vasorelaxant effect of EFCS on rat mesenteric arterial bed, which is dependent of muscarinic receptor activation, nitric oxide, and EDHF, can account for potential therapeutic use against high blood pressure related cardiovascular diseases.

ATP Released in Response to Angiotensin II Contributes to Vasoconstriction in the Rat Mesenteric Arterial Bed in a Sex‐dependent Manner

While vascular tone is affected by multiple mediators released from various component tissues, it has been a long-held belief that the mechanical act of vascular smooth muscle contraction induces ATP release regardless of the stimulus that initiated vasoconstriction. Contrary to this theory, here we present evidence that the release of ATP by vascular smooth muscle is both agonist- and sex-dependent. By utilizing a near-real time luminometric technique developed by our lab, we found that while methoxamine, 5-hydroxytryptamine, and angiotensin II all induced vasoconstriction in the rat mesenteric arterial bed, only angiotensin II caused ATP release. Furthermore, this response was only seen in preparations from male rats, whereas those from female rats showed no ATP release in response to any of the three vasoactive agents tested, indicating a sex difference in this process. When we further investigated the ATP release and perfusion pressure responses to angiotensin II, we found that both were inhibited by losartan, indicating the involvement of AT1 receptors. The nonselective P2 antagonist suramin blocked a significant portion of angiotensin II-stimulated vasoconstriction, suggesting that the action of ATP on P2 receptors may play a critical role in the ability of angiotensin II to cause vasoconstriction. A similar response was seen when angiotensin II was perfused along with NF449, a selective inhibitor of the P2X1 receptor. Angiotensin II-induced ATP release was inhibited by carbenoxolone, a nonspecific gap junction blocker which is known to inhibit pannexin-1 channels, suggesting that this may be the conduit through which this release occurs. Taken together, our findings suggest that activation of vascular AT1 receptors by angiotensin II directly constricts smooth muscle while simultaneously opening carbenoxolone-sensitive channels allowing ATP to be released. This ATP then activates vascular P2X1 receptors, augmenting the AT1-induced vasoconstriction. This process occurs in the mesenteric arterial bed taken from male, but not female, rats.

Abstract P135: Angiotensin II, But Not Methoxamine Or 5-HT, Causes ATP Release in the Rat Mesenteric Arterial Bed

The control of vascular caliber relies on mediators released from multiple components of the vascular neuroeffector junction. These mediators include ATP, which is released from the sympathetic nerves from vesicles that also contain norepinephrine, as well as from the vascular smooth muscle (VSM) via pannexin-1 (panx-1) channels. We hypothesize that VSM-derived ATP plays a critical role in balancing the vasoactive effects of mediators at the vascular neuroeffector junction. Panx-1 channel opening on VSM has been reported to be stimulated by caspase cleavage, cytoplasmic Ca 2+ , and extracellular K + , but the effects of VSM GPCR activation are not as well characterized. Here we utilize a near-real time luminometric technique to quantify the release of ATP from the rat mesenteric arterial bed in response to vasoconstrictor agonists. We observed disparate effects of three physiologically relevant vasoactive agents, and these do not correlate with the relative changes in perfusion pressure. Whereas angiotensin II caused a robust release of ATP (228.6 ± 31.94 nM), no significant release was observed with either methoxamine (an α 1 agonist; 44.41 ± 31.94 nM) or 5-HT (0 ± 0 nM) . These results indicate that GPCR-mediated smooth muscle contraction is not sufficient to induce ATP release in this vascular bed. This is an important first step toward understanding the role of ATP in the vasculature.

Moringa oleifera leaf extract lowers high blood pressure by alleviating vascular dysfunction and decreasing oxidative stress in L-NAME hypertensive rats

BackgroundEnhancing relaxation of resistance arteries and decreasing oxidative stress by using natural products are potential strategies for prevention and treatment of hypertension. PurposeThis study investigated whether aqueous extract of Moringa oleifera leaves (MOE) could alleviate Nω-nitro-L-arginine-methyl ester (L-NAME)-induced high blood pressure via modulation of vascular function and antioxidant properties. MethodsAn experimental hypertensive model was established by administration of L-NAME (50 mg/kg/day) in drinking water to male Wistar rats for 3 weeks. Arterial pressure was measured indirectly by tail-cuff plethysmography and directly via femoral artery catheterization. Vasoreactivity of isolated rat mesenteric arterial bed was determined by the changes in perfusion pressure detected by a pressure transducer. Vascular superoxide anion (O2•−) production was determined by lucigenin-enhanced chemiluminescence. Other biochemical measurements including malondialdehyde (MDA) level, superoxide dismutase (SOD), and catalase (CAT) activities were measured by colorimetric assay. ResultsL-NAME-treated rats developed significantly increased blood pressure and heart rate. Concurrent oral treatment with MOE (30 and 60 mg/kg/day) could decrease the high blood pressure and tachycardia in a dose-dependent manner. MOE reduced the impairment of acetylcholine-induced relaxation and decreased the hyperreactivity of adrenergic-mediated contraction in response to periarterial nerve stimulation and phenylephrine in isolated mesenteric arterial beds. In addition, MOE exhibited antioxidant effects in the hypertensive rats, as indicated by suppression of vascular O2•− production, decrease of plasma and thoracic aorta MDA levels, and increase of antioxidant activities of SOD and CAT. Moreover, MOE (0.001–0.3 mg) produced a dose-dependent relaxation in methoxamine pre-contracted arterial beds isolated from L-NAME hypertensive rats, which was abolished by endothelium denudation. ConclusionThese findings suggest that the antihypertensive effect of MOE in L-NAME-hypertensive rats may be mediated by alleviating vascular dysfunction and oxidative stress and promoting endothelium-dependent vasorelaxation. MOE may be potentially useful as a natural product against hypertension.

Endothelium-Independent Vasorelaxant Effect of Synthesized 2 Hydroxymethylchromone on Rat Mesenteric Arterial Bed

Background: Several synthesized chromones derivatives have been found to promote intense vasodilation and antihypertensive activity. 2 hydroxymethylchromone (2HMC) is a benzopyrane derivative that vasodilator effect on small arteries has not yet been investigated. This study describes its synthesis, examines any vasodilator effect observed, and clarifies its mechanism of action in rat mesenteric arterial bed (MAB). Material and Method: Intact and denuded rat mesenteric arterial bed pre-contracted with PHE (2-4 ng/mL) was exposed to bolus injections of 2HMC (3-1000 µg). The effect of the latter was also studied in the presence of specific inhibitors such as L-NAME, indomethacine, atropine, glybenclamide, tetraethylammonium, BaCl2 and apamin. The effect of 2HMC on restricted calcium influx and calcium release from sarcoplasmic reticulum was investigated. Results: The data show that bolus injections of 2HMC induced in a dose dependent manner, a reversible vasorelaxant effect on pre-contracted preparations. This effect remained unaltered by endothelium removal and was not significantly affected by L-NAME, indomethacine, atropine, glybenclamide, BaCl2 tetraethylammonium or apamin. On the contrary, 2HMC significantly shifted to the right the concentration-response curve to high K+-induced MAB contraction during Ca2+ supplementation. Also, 2HMC strongly reduced the response to PHE when the MAB(s) were maintained under calcium-free conditions. Conclusion: Our results suggest that 2HMC-induced vasorelaxation is not mediated via the endothelium pathways, but rather might be due at least to both antagonistic action on extracellular calcium influx (blockade of voltage operated calcium channels) and restriction of calcium mobilization from intracellular stores. Keywords: Chromones, 2-hydroxymethyl-4H-1-benzopyran-4-one, endothelium-independent, vasodilatation, rat mesenteric arterial bed, VOCCs blockade, restriction of intracellular Ca2+ release, perfusion pressure, smooth muscle.

Naturally occurring anthocyanin cyanidin-3-rutinoside possesses inherent vasorelaxant actions and prevents methylglyoxal-induced vascular dysfunction in rat aorta and mesenteric arterial bed

Cyanidin-3-rutinoside (C3R) possesses anti-oxidant, anti-inflammatory and anti-glycation properties. Methylglyoxal (MG), a highly reactive dicarbonyl aldehyde by-product of glycolysis, is a precursor of advanced glycation end products and contributes to vascular dysfunction, particularly during hyperglycemia. We investigated the possible inherent vasoactivity of C3R, and its effectiveness against MG-induced vascular abnormalities in isolated blood vessel preparations from male Wistar Kyoto rat. C3R induced vasorelaxation concentration-dependently in aortic rings (92% maximum relaxation; EC50: 2.43±0.57μM) and in perfused-mesenteric arterial bed (61% maximum relaxation; EC50: 25.0±1.26μM) pre-contracted with noradrenaline (NA). The vasorelaxation actions of C3R were endothelium-dependent and mediated primarily via nitric oxide (NO) as evidenced by the absence of relaxation in endothelium-denuded preparations as well as in the presence of Nω-nitro-l-arginine, an inhibitor of NO synthase. Intravenous administration of C3R (15–25μmol/kg body weight) in anesthetized rats significantly reduced mean arterial blood pressure (11–23%). Pre-treatment with MG (500μM) potentiated the vasoconstriction elicited by NA and impaired vasorelaxation induced by acetylcholine that was fully restored to basal levels in the presence of C3R (3μM). Taken together, C3R exerts multiple benefits on the vasculature, complementing its potential as a candidate anti-glycation agent.

Reactive oxygen species derived from NAD(P)H oxidase play a role on ethanol-induced hypertension and endothelial dysfunction in rat resistance arteries.

Chronic ethanol consumption is a risk factor for cardiovascular diseases. We studied whether NAD(P)H oxidase-derived reactive oxygen species (ROS) play a role in ethanol-induced hypertension, vascular dysfunction, and protein expression in resistance arteries. Male Wistar rats were treated with ethanol (20% v/v) for 6weeks. Ethanol treatment increased blood pressure and decreased acetylcholine-induced relaxation in the rat mesenteric arterial bed (MAB). These responses were attenuated by apocynin (30mg/kg/day; p.o. gavage). Ethanol consumption increased superoxide anion (O2-) generation and decreased nitrate/nitrite (NO x ) concentration in the rat MAB and apocynin prevented these responses. Conversely, ethanol did not affect the concentration of hydrogen peroxide (H2O2) and reduced glutathione (GSH) or the activity of superoxide dismutase (SOD) and catalase (CAT) in the rat MAB. Ethanol increased interleukin (IL)-10 levels in the rat MAB but did not affect the levels of tumor necrosis factor (TNF)-α, IL-6, or IL-1β. Ethanol increased the expression of Nox2 and the phosphorylation of SAPK/JNK, but reduced eNOS expression in the rat MAB. Apocynin prevented these responses. However, ethanol treatment did not affect the expression of Nox1, Nox4, p38MAPK, ERK1/2, or SAPK/JNK in the rat MAB. Ethanol increased plasma levels of TBARS, TNF-α, IL-6, IL-1β, and IL-10, whereas it decreased NO x levels. The major finding of our study is that NAD(P)H oxidase-derived ROS play a role on ethanol-induced hypertension and endothelial dysfunction in resistance arteries. Moreover, ethanol consumption affects the expression and phosphorylation of proteins that regulate vascular function and NAD(P)H oxidase-derived ROS play a role in such responses.

Nitric oxide and Kir6.1 potassium channel mediate isoquercitrin-induced endothelium-dependent and independent vasodilation in the mesenteric arterial bed of rats

The vascular effect of flavonoid isoquercitrin was investigated in the perfused mesenteric vascular bed of rats. In preparations with functional endothelium isoquercitrin (100, 300 and 1000nmol) dose-dependently reduced the perfusion pressure by 13±2.2, 33±3.9, and 58±3.7mm Hg, respectively. Endothelium removal or inhibition of the nitric oxide synthase enzymes by l-NAME did not change the effects of 100 and 300 nmol isoquercitrin, but reduced by 30–40% the vasodilation induced by 1000 nmol isoquercitrin. Perfusion with nutritive solution containing 40mM KCl abolished the vasodilatory effect of all isoquercitrin doses. Treatment with glibenclamide, a Kir6.1 (ATP-sensitive) potassium channel blocker, inhibited vasodilation induced by 100 and 300 nmol isoquercitrin, but only partially reduced the effect of 1000 nmol isoquercitrin. The non-selective KCa (calcium-activated) potassium channel blocker tetraethylammonium, but not the selective KCa1.1 channel blocker iberiotoxin, reduced by around 60% vasodilation induced by all isoquercitrin doses. In addition, association of tetraethylammonium and glibenclamide, or l-NAME and glibenclamide, fully inhibited isoquercitrin-induced vasodilation. Our study shows that isoquercitrin induces vasodilation in resistance arteries, an effect mediated by K+ channel opening and endothelial nitric oxide production.

Angiotensin type 1 receptor mediates chronic ethanol consumption-induced hypertension and vascular oxidative stress

ObjectivesWe hypothesized that chronic ethanol intake enhances vascular oxidative stress and induces hypertension through renin–angiotensin system (RAS) activation. Methods and resultsMale Wistar rats were treated with ethanol (20% v/v). The increase in blood pressure induced by ethanol was prevented by losartan (10mg/kg/day; p.o. gavage), a selective AT1 receptor antagonist. Chronic ethanol intake increased plasma renin activity (PRA), angiotensin converting enzyme (ACE) activity, plasma angiotensin I (ANG I) and angiotensin II (ANG II) levels and serum aldosterone levels. No differences on plasma osmolality and sodium or potassium levels were detected after treatment with ethanol. Ethanol consumption did not alter ACE activity, as well as the levels of ANG I and ANG II in the rat aorta or mesenteric arterial bed (MAB). Ethanol induced systemic and vascular oxidative stress (aorta and MAB) and these effects were prevented by losartan. The decrease on plasma and vascular nitrate/nitrite (NOx) levels induced by ethanol was prevented by losartan. Ethanol intake did not alter protein expression of ACE, AT1 or AT2 receptors in both aorta and MAB. Aortas from ethanol-treated rats displayed decreased ERK1/2 phosphorylation and increased protein expression of SAPK/JNK. These responses were prevented by losartan. MAB from ethanol-treated rats displayed reduced phosphorylation of p38MAPK and ERK1/2 and losartan did not prevent these responses. ConclusionsOur study provides novel evidence that chronic ethanol intake increases blood pressure, induces vascular oxidative stress and decreases nitric oxide (NO) bioavailability through AT1-dependent mechanisms.

Acute ethanol intake induces mitogen-activated protein kinase activation, platelet-derived growth factor receptor phosphorylation, and oxidative stress in resistance arteries.

In the present study, we investigated the role of angiotensin type I (AT1) receptor in reactive oxygen species (ROS) generation and mitogen-activated protein kinases (MAPK) activation induced by acute ethanol intake in resistance arteries. We also evaluated the effect of ethanol on platelet-derived growth factor receptors (PDGF-R) phosphorylation and the role of this receptor on ROS generation by ethanol. Ethanol (1g/kg; p.o. gavage) effects were assessed within 30min in male Wistar rats. Acute ethanol intake did not alter angiotensin I or angiotensin II levels in the rat mesenteric arterial bed (MAB). Ethanol induced vascular oxidative stress, and this response was not prevented by losartan (10mg/kg; p.o. gavage), a selective AT1 receptor antagonist. MAB from ethanol-treated rats displayed increased SAPK/JNK and PDGF-R phosphorylation, responses that were not prevented by losartan. The phosphorylation levels of protein kinase B (Akt) and eNOS were not affected by acute ethanol intake. MAB nitrate levels and the reactivity of this tissue to acetylcholine, phenylephrine, and sodium nitroprusside were not affected by ethanol intake. Ethanol did not alter plasma antioxidant capacity, the levels of reduced glutathione, or the activities of superoxide dismutase and catalase in the rat MAB. Short-term effects of ethanol (50mmol/l) were evaluated in vascular smooth muscle cells (VSMC) isolated from rat MAB. Ethanol increased ROS generation, and this response was not affected by AG1296, a PDGF-R inhibitor, or losartan. Finally, ethanol did not alter MAPK or PDGF-R phosphorylation in cultured VSMC. Our study provides novel evidence that acute ethanol intake induces ROS generation, PDGF-R phosphorylation, and MAPK activation through AT(1)-independent mechanisms in resistance arteries in vivo. MAPK and PDGF-R play a role in vascular signaling and cardiovascular diseases and may contribute to the vascular pathobiology of ethanol.

CGRP release from perivascular capsaicin‐sensitive sensory nerves regulates vascular function through pannexin‐1 channel opening (1075.4)

Resistance arteries are inervated by capsaicin‐sensitive sensory nerves (CSSNs) that release calcitonin gene‐related peptide (CGRP). CGRP is a vasodilator, but its participation in the regulation of vascular signaling has not been explored. We assessed if CSSNs regulate the expression of key proteins involved in the control of vascular function. The isolated mesenteric arterial bed of rat was perfused with 1 µM capsaicin for 20 min. Protein expression was evaluated by Western blot and cell permeability through hemichannels such as pannexin (Panx) channels was assessed by ethidium uptake. Expression of eNOS and Panx‐1, but not connexin (Cx) 32, Cx43 or Panx‐2, was reduced 3 h after capsaicin treatment. CGRP8‐37, a CGRP‐1 receptor blocker, or probenecid, a Panx‐1 channel inhibitor, prevented the reduction of eNOS and Panx‐1 levels. Capsaicin and CGRP (100 nM) increased ethidium uptake in mesenteric arteries, but only CGRP in cultured endothelial cells. Capsaicin‐ or CGRP‐induced ethidium uptake was prevented by CGRP8‐37, probenecid, KT‐5720 (PKA inhibitor) or NG‐nitro‐L‐arginine (NOS blocker). These data suggest that transient activation of CSSNs leads to down‐regulation of eNOS and Panx‐1 expression by a Panx‐1 channel‐dependent pathway. Panx‐1 channel opening depends on CGRP‐1 receptor activation, which initiates a PKA‐mediated signaling and NO production.Grant Funding Source: Supported by FONDECYT 1100850 and AT 24121388.

Endothelium-dependent vascular relaxation induced by Globularia alypum extract is mediated by EDHF in perfused rat mesenteric arterial bed

The vasodilatory effect of Globularia alypum L. (GA) extract was evaluated in rat mesenteric arterial bed pre-contracted by continuous infusion of phenylephrine (2-4 ng/mL). Bolus injections of GA elicited dose-response vasodilation, which was abolished after endothelium removal. Addition of a nitric oxide synthase inhibitor, N(G)-nitro-l-arginine methyl ester (100 µmol/L), alone or in the presence of a cyclooxygenase inhibitor, indomethacin (10 µmol/L), did not significantly affect the vasodilation of the mesenteric arterial bed in response to GA extract. These results suggest that GA-induced vasodilation is endothelium dependent but nitric oxide and prostacyclin independent. In the presence of high K(+) (60 mmol/L), the GA vasodilatory effect was completely abolished, suggesting that the vasodilation effect is mediated by hyperpolarization of the vascular cells. Also, pre-treatment with atropine (a muscarinic receptors antagonist) antagonized the GA-induced vasodilation, suggesting that the vasodilatory effect is mainly mediated by the endothelium-derived hyperpolarizing factor through activation of endothelial muscarinic receptors.

Vasoconstrictor and vasodilator responses to tryptamine of rat‐isolated perfused mesentery: comparison with tyramine and β‐phenylethylamine

BACKGROUND AND PURPOSETryptamine increases blood pressure by vasoconstriction, but little is known about its actions on the mesentery, in particular the resistance arteries. Tryptamine interacts with trace amine-associated receptors (TAARs) and because of its structural similarity to 5-HT, it may also interact with 5-HT receptors. Our hypothesis is therefore that the rat mesenteric arterial bed will exhibit vasopressor and vasodepressor responses to tryptamine via both 5-HT and TAARs.EXPERIMENTAL APPROACHTryptamine-evoked responses were assayed from pressure changes of the rat-isolated mesenteric vasculature perfused at constant flow rate in the absence and presence of adrenoceptor and 5-HT receptor antagonists.KEY RESULTSTryptamine caused dose-dependent vasoconstriction of the mesenteric arterial bed as increases in perfusion pressure. These were unaffected by the α1-adrenoceptor antagonist, prazosin, but were attenuated by the non-selective α-adrenoceptor antagonist, phentolamine. The 5-HT2A receptor antagonists, ketanserin and ritanserin, abolished the tryptamine-induced pressure increases to reveal vasodilator responses in mesenteric beds preconstricted with phenylephrine. These tryptamine-induced vasodilator responses were unaffected by the 5-HT7 receptor antagonist, SB269970, but were eliminated by the NOS inhibitor, Nω-nitro-L-arginine methyl ester (L-NAME). Tyramine and β-phenylethylamine also caused vasodilatation in pre-constricted vasculature, which was also abolished by L-NAME.CONCLUSIONS AND IMPLICATIONSTryptamine causes vasoconstriction of the mesenteric vasculature via 5-HT2A receptors, which when inhibited exposed vasorelaxant effects in pre-constricted tissues. The vasodilatation was independent of 5-HT2A and 5-HT7 receptors but like that for tyramine and β-phenylethylamine was due to NO release. Potency orders suggest TAAR involvement in the vasodilatation by these trace amines.

Carboxypeptidases A1 and A2 from the perfusate of rat mesenteric arterial bed differentially process angiotensin peptides

Here we report the isolation of carboxypeptidases A1 and A2 (CPA1 and CPA2) from the rat mesenteric arterial bed perfusate, which were found to be identical with their pancreatic counterparts. Angiotensin (Ang) I, Ang II, Ang-(1-9) and Ang-(1-12) were differentially processed by these enzymes, worthy mentioning the peculiar CPA1-catalyzed conversion of Ang II to Ang-(1-7) and the CPA2-mediated formation of Ang I from Ang-(1-12). We detected gene transcripts for CPA1 and CPA2 in mesentery and other extrapancreatic tissues, indicating that these CPAs might play a role in the renin–angiotensin system in addition to their functions as digestive enzymes.

Ethanol Consumption Alters the Expression and Reactivity of Adrenomedullin in the Rat Mesenteric Arterial Bed

Adrenomedullin (AM) is a peptide that displays cardiovascular protective activity. We investigated the effects of chronic ethanol consumption on arterial blood pressure, vascular reactivity to AM and the expression of AM system components in the rat mesenteric arterial bed (MAB). Male Wistar rats were treated with ethanol (20% vol/vol) for 6 weeks. Systolic, diastolic and mean arterial blood pressure were monitored in conscious rats. Vascular reactivity experiments were performed on isolated rat MAB. Matrix metalloproteinase-2 (MMP-2) levels were determined by gelatin zymography. Nitrite and nitrate generation were measured by chemiluminescence. Protein and mRNA levels of pre-pro-AM, CRLR (calcitonin receptor-like receptor) and RAMP1, 2 and 3 (receptor activity-modifying proteins) were assessed by western blot and quantitative real-time polymerase chain reaction, respectively. Ethanol consumption induced hypertension and decreased the relaxation induced by AM and acetylcholine in endothelium-intact rat MAB. Phenylephrine-induced contraction was increased in endothelium-intact MAB from ethanol-treated rats. Ethanol consumption did not alter basal levels of nitrate and nitrite, nor did it affect the expression of MMP-2 or the net MMP activity in the rat MAB. Ethanol consumption increased mRNA levels of pre-pro-AM and protein levels of AM in the rat MAB. Finally, no differences in protein levels or mRNA of CRLR and RAMP1, 2 and 3 were observed after treatment with ethanol. Our study demonstrates that ethanol consumption increases blood pressure and the expression of AM in the vasculature and reduces the relaxation induced by this peptide in the rat MAB.

N G-Nitro-l-arginine methyl ester attenuates vasodilator responses to acetylcholine but enhances those to sodium nitroprusside

The effects of NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of the synthesis of the endothelium-derived relaxing factor nitric oxide, were studied in two isolated perfused vascular beds: the rat mesenteric arterial bed and the hepatic arterial bed of the rabbit liver. The tone of both preparations was raised with noradrenaline (10 and 30 microM for rabbit and rat preparations, respectively). In both preparations, L-NAME (30 microM) significantly attenuated vasodilator responses to the endothelium-dependent vasodilator acetylcholine, but enhanced responses to sodium nitroprusside (a direct smooth muscle dilator). The evidence supports the view, previously established from work carried out in isolated vessels, that in addition to acting as an inhibitor of nitric oxide, L-NAME enhances the responsiveness of smooth muscle to direct relaxation by nitrovasodilators.

Hydrogen Sulfide-Induced Dual Vascular Effect Involves Arachidonic Acid Cascade in Rat Mesenteric Arterial Bed

Hydrogen sulfide (H(2)S), a novel gaseous transmitter, is considered a physiological regulator of vascular homeostasis. Recent evidence suggests H(2)S as an endothelium-hyperpolarizing factor (EDHF) candidate. To address this issue, we evaluated the vascular effect of sodium hydrogen sulfide (NaHS), an H(2)S donor, on the rat mesenteric arterial bed. NaHS concentration-response curve was performed on preconstricted mesenteric arterial bed. To assess the contribution of EDHF, we performed a pharmacologic dissection using indomethacin, N(G)-nitro-l-arginine methyl ester (l-NAME), or apamin and charybdotoxin as cyclooxygenase, nitric-oxide synthase, and calcium-dependent potassium channel inhibitors, respectively. In another set of experiments, we used 4-(4-octadecylphenyl)-4-oxobutenoic acid, baicalein, or proadifen as phospholipase A(2) (PLA(2)), lipoxygenase, and cytochrome P450 inhibitors, respectively. Finally, an immunofluorescence study was performed to support the involvement of PLA(2) in mesenteric artery challenged by NaHS. NaHS promoted a dual vascular effect (i.e., vasoconstriction and vasodilation). l-NAME or baicalein administration affected neither NaHS-mediated vasodilation nor vasoconstriction, whereas apamin and charybdotoxin significantly inhibited NaHS-induced relaxation. Pretreatment with PLA(2) inhibitor abolished both the contracting and the relaxant effect, whereas P450 cytochrome blocker significantly reduced NaHS-mediated relaxation. The immunofluorescence study showed that NaHS caused a migration of cytosolic PLA(2) close to the nucleus, which implicates activation of this enzyme. Our data indicate that H(2)S could activate PLA(2), which in turn releases arachidonic acid leading, initially, to vasoconstriction followed by vasodilation mediated by cytochrome P450-derived metabolites. Because EDHF has been presumed to be a cytochrome P450 derivative of the arachidonic acid, our results suggest that H(2)S acts through EHDF release.

Dietary flaxseed supplementation improves endothelial function in the mesenteric arterial bed

Abstract The aim of this study was to evaluate the influence of flaxseed diet supplementation on endothelial function in the mesenteric arterial bed of rats. Twenty-four rats were divided into 3 groups: Control Group (CG; 10% protein; 5% fiber; 7% lipid); Flaxseed Group (FG, supplemented with 25% flaxseed; 10% protein; 7% fiber; 11% lipid); and Modified Control Group (MCG; 10% protein; 7% fiber; 11% lipid). The blood was obtained by cardiac puncture (after 180 days) and the serum was separated for lipid profile analyses. The vasodilator effect of acetylcholine (1–100 pmol) was evaluated in the preconstricted isolated rat vascular bed. FG showed a 47% increase in HDL-C, a 22% reduction in LDL-C, a 23% reduction in triacylglycerols, and an increased ( p

Angiotensin (1–7) Induced Inhibition of the Nerve‐Stimulation Induced Release of Norepinephrine (NE) and Neuropeptide Y (NPY) from the Rat Mesenteric Arterial Bed: Role of Prostacyclin

We have observed that Ang‐(1‐7) produces a significant decrease in the nerve stimulation (NS)‐induced release of both NE and NPY as well as perfusion pressure of the perfused mesenteric arterial bed of the rat. In the present study we examined the hypothesis that the Ang‐(1‐7) induced inhibition of sympathetic neurotransmission is mediated at least in part by prostacyclin (PGI2), which is well known to inhibit sympathetic neurotransmission and to mediate part of the vasodilator action of Ang‐(1‐7). Experiments were carried out using the mesenteric arterial bed obtained from 10–12 week old Sprague Dawley and Spontaneously Hypertensive Rats (SHR). The effect of Ang‐(1‐7) on the NS‐evoked release of NE and NPY was determined before and after the administration of indomethacin to block PGI2 synthesis and before and after the administration of the PGI2 receptor blocker CAY 10441. Results obtained to date support our hypothesis that PGI2 mediates the actions of Ang‐(1‐7). (Supported by HL60260 and NIGMS008306)