Rat Mesenteric Vascular Bed Research Articles

Functional effects of visfatin in isolated rat mesenteric small resistance arteries

A new adipocytokine, visfatin is expressed in perivascular adipose tissue (PVAT) and exerts effects on vascular system in addition to its relationship with various pathological conditions. The present study aimed to investigate the functional effects of visfatin and the possible underlying mechanism(s) of the effects of visfatin in isolated rat mesenteric small resistance arteries. The study was conducted in small resistance arterial rings isolated from rat mesenteric vascular beds. While visfatin incubation did not produce significant alterations in contractile responses of mesenteric arterial rings to noradrenaline, relaxation responses to acetylcholine but not to sodium nitroprusside (SNP) were significantly reduced in endothelium-intact rings. The inhibitory effect of visfatin on responses to acetylcholine was not observed in endothelium-denuded preparations. Incubation of tissues with nicotinamide phosphoribosyl transferase (NAMPT) inhibitor FK866 or superoxide dismutase (SOD) reversed the inhibitory effects of visfatin on relaxation responses to acetylcholine. Co-incubation of visfatin with Nω-nitro-L-arginine methylester (L-NAME) did not produce a significant alteration in vascular responses to acetylcholine compared to L-NAME incubation alone. Mesenteric PVAT visfatin levels were significantly higher than and correlated positively with plasma visfatin levels. The results of our study indicated that visfatin-induced reductions in endothelium-dependent relaxations of rat isolated small resistance arteries are mediated by oxygen free radicals and a reduction in nitric oxide (NO) bioavailability. It was suggested that increment in systemic and/or local visfatin levels due to various pathologies including obesity and excessive weight gain may play a substantial role in initiation and/or propagation of vascular dysfunctions.

Phytochemical evaluation and vasodilatory activity of O. elongatum, C. salviifolius and C. laurifolius

The high blood pressure is one of the main causes of death and cardiovascular diseases. Vasodilator medications are frequently used to treat arterial hypertension. The aim of this study was to evaluate vasodilator properties of three plants from North of Morocco then to quantify phenolic compounds and flavonoids in each plant extracts. The leaves of Origanum elongatum, Cistus salviifolius and Cistus laurifolius were extracted with hexane, methanol and ethyl acetate by ultrasonic apparatus. The total phenolic content, analyzed using Folin–Ciocalteu’s reagent, of the samples varied from 46.6 µg/100 mg to 153 µg/100 mg dry weight, expressed as gallic acid equivalents (GAE). The total flavonoid concentrations, detected using 2% aluminum chloride, varied from 3.63 to 5.54 µg equivalents (RE)/mg dry weight. Under different plant growth regulators induce a vasodilator effect on Wistar rat mesenteric vascular bed pre-contracted with norepinephrine. for O.elongatum, the methanolic extracts at (PP = 50 mmHg) were found to be more active than the acetylcholine with a concentration of 10 -4 M taken as a reference (PP = 40 mmHg) and The vasodilator activity of methanolic extract of Cistus laurifolius at 100 μg/ml is the same as the reference (PP=40 mmHg). the vasodilator activity found in the three plants studied is due to their antioxidant power.

Centaurium Erythraea Extracts Exert Vascular Effects through Endothelium- and Fibroblast-dependent Pathways.

Centaurium erythraea is a plant used in traditional medicine for several cardiovascular disorders, namely hypertension, but there is no scientific evidence able to provide a molecular basis for its claimed antihypertensive effects. After a preliminary screen of extracts obtained from sequential extraction of C. erythraea aerial parts, effects of the methanolic fraction (MFCE) on changes in perfusion pressure of isolated rat mesenteric vascular bed (MVB) and in rat cardiac fibroblasts proliferation were investigated, gathering information on the mechanisms involved in endothelium-dependent effects and their dependence on a pro-proliferative stimulus. The HPLC-DAD determination of the phenolics content of MFCE revealed the presence of 22 phenolic compounds. MFCE reduced (63.3 ± 3.9%; n = 4) perfusion pressure in MVB and almost completely abrogated the Ang II-induced increase in cardiac fibroblasts proliferation. Reduction of the perfusion pressure caused by MFCE was endothelium-dependent and occurred in parallel with an increase in NO release. These effects were inhibited by muscarinic receptor antagonists, by L-NAME (a NO synthase inhibitor), and by ODQ (a soluble guanylate cyclase inhibitor). Experiments revealed that effects required the involvement of K+ channels, being inhibited by tetraethylamonium (TEA; a Ca2+ activated K+ channels inhibitor) and by glibenclamide (an ATP-sensitive K+ channels inhibitor). In conclusion, extracts from C. erythraea, particularly the compounds present in the MFCE, induce endothelium-dependent vasodilation and prevent fibroblast proliferation induced by angiotensin II, which can account for the claimed antihypertensive effects of C. erythraea in traditional medicine.

Influence of photoactivated coproporphirin on microcirculation

The aim –to investigate the effect of photoactivated coproporphyrin III (KP III) on microcirculation in the rat mesenteric vascular bed. Material and methods. The study was performed on 20 male rats, divided into 4 groups: 1) control; 2) KP III; 3) laser irradiation; 4) laser irradiation on combined with prior administration of the KP III.The objectof the study was venules (20–40 µm) of the mesentery of the small intestine. The study of blood flow velocity in the venules was performed using the method of intravital biomicroscopy. The velocity parameters were registered using a high-speed video camera Basler acA2000 (Germany). Coproporphyrin III (Elast, Russia) at a dose of 10 mg/kg was injected into the tail vein 3 hours before laser irradiation. Irradiation was performed using a Lakhta Milon semiconductor laser apparatus (Qualitek, Russia) (λ=635 nm, 0.1 W/cm2 ; 300 s; 30 J/cm2 ).Results.Administration of KP III without subsequent irradiation did not affect the blood flow velocity during the entire observation period. Laser irradiation of venules without prior administration of KP III led to an increase in blood flow velocity by 39.1 % (p<0.05). After laser irradiation and administration of KPIII, there was a gradual decrease in flow velocity after the photoactivation process.Conclusions. We studied the effect of photoactivated KP III on microcirculation in the mesentery of the small intestine of rats. Changes in the blood flow velocity in the venules of the mesentery affected by KP III and laser irradiation develop mainly in the post-radiation period and could be associated with endothelial dysfunction.

English

There are reports of the presence of vasodilatory alkaloids in Heimia salicifolia extracts. The action mechanisms of the potential antihypertensive effect of such alkaloids have not however, been elucidated. The objective of the present study was to corroborate the antihypertensive and vasorelaxant activities of the isolated alkaloids from H. salicifolia, and to characterize their vasorelaxant actions. A chloroform extract (HSCE) was obtained from H. salicifolia. The alkaloids were separated by thin layer chromatography, extracted from silica gel, and evaluated using spectroscopy. The alkaloid with the most potent vasorelaxant activity was identified as lythrine. The antihypertensive effect of the HSCE was corroborated on normotensive rats and on animals with Nω-nitro-L-arginine-methyl ester (L-NAME) induced hypertension. The action mechanisms of the HSCE and lythrine were studied on isolated and perfused rat mesenteric vascular bed (MVB) preparations. HSCE administration produced a concentration-dependent relaxation, but in preparations without vascular endothelium, the relaxant response to HSCE was significantly diminished. In MVB preparations with intact vascular endothelium, pre-contracted with phenylephrine or L-NAME, perfusion with lythrine produced concentration-dependent relaxation; a similar effect was produced by acetylcholine. Wortmannin (phosphatidylinositol 3-kinase inhibitor) and methylene blue (guanylate cyclase inhibitor) decreased the relaxant effect of lythrine. These data suggest that the vascular relaxation induced by alkaloids isolated from H. salicifolia is dependent on the activation of the nitric oxide/guanylate cyclase pathway. Key words: Heimia salicifolia, lythrine alkaloid, hypertension, Nω-nitro-L-arginine-methyl ester (L-NAME), mesenteric vascular bed. &nbsp

Fructose intake exacerbates the contractile response elicited by norepinephrine in mesenteric vascular bed of rats via increased endothelial prostanoids

Chronic fructose intake induces major cardiovascular and metabolic disturbances and is associated with the development of hypertension due to changes in vascular function. We hypothesized that high fructose intake for 6 weeks would cause metabolic syndrome and lead to initial vascular dysfunction. Male Wistar rats were assigned to receive fructose (FRU, 10%) or drinking water (CON) for 6 weeks. Systolic blood pressure was evaluated by tail plethysmography. Fasting glucose, insulin and glucose tolerance were measured at the end of the follow-up. Mesenteric vascular bed reactivity was tested before and after pharmacological blockade. Western blot analysis was performed for iNOS, eNOS, Nox2 and COX-2. DHE staining was used for vascular superoxide anion detection. Vessel structure was evaluated by optical and electronic microscopy.Fructose intake did not alter blood pressure, but did increase visceral fat deposition and fasting glucose as well as impair insulin and glucose tolerance. Fructose increased NE-induced vasoconstriction compared with CON, and this difference was abrogated by indomethacin perfusion as well as endothelium removal. ACh-induced relaxation was preserved, and the NO modulation tested after L-NAME perfusion was similar between groups. SNP-induced relaxation was not altered. Inducible NOS was increased; however, there were no changes in eNOS, Nox2 or COX-2 protein expression. Basal or stimulated superoxide anion production was not changed by fructose intake. In conclusion, high fructose intake increased NE-induced vasoconstriction through the endothelial prostanoids even in the presence of a preserved endothelium-mediated relaxation. No major changes in vessel structure were detected.

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.

Dose-dependent Differential Mechanism of Quercetin-induced Vasodilatations in Isolated Perfused Rat Mesenteric Vascular Bed

Dose-dependent Differential Mechanism of Quercetin-induced Vasodilatations in Isolated Perfused Rat Mesenteric Vascular Bed

Vascular responses to compound 48/80 in rat mesenteric vascular beds.

A further investigation was performed on the vascular effect of endogenous histamine using the histamine releaser, compound 48/80, in rat mesenteric vascular beds with active tone. In preparations with intact endothelium, low concentrations of compound 48/80 (1.53 × 10(-5) - 3 × 1.53 × 10(-5) mg/mL) perfusion for 1 min only induced a small vasodilation. High concentrations of compound 48/80 (1.53 × 10(-4) - 3 × 1.53 × 10(-2) mg/mL) induced a biphasic vascular responses, an initial vasoconstriction followed a subsequent long-lasting vasodilation. The vasodilation induced by low concentrations of compound 48/80 and the vasoconstriction induced by high concentration of compound 48/80 was inhibited by olopatadine. However, cimetidine did not affect the responses induced by compound 48/80. Endothelium removal enlarged the compound 48/80-induced phase-2 vasoconstriction, while it attenuated the phase-3 vasodilation. Additionally, indomethacin and seratrodast significantly inhibited vasoconstriction but it did not affect the long-lasting vasodilation induced by high concentrations of compound 48/80. Ruthenium red inhibited the vasodilation induced by low concentrations and high concentrations of compound 48/80. These results suggest that the vasoconstriction induce by high concentrations of compound 48/80 is mediated by endogenous histamine released from mast cells. It is also suggested that thromboxane A2 released from mast cells is related to the vasoconstriction.

The production of vasoconstriction-induced residual NO modulates perfusion pressure in rat mesenteric vascular bed

In the presence of nitric oxide synthase (NOS) inhibitors, the contribution of residual NO to endothelium-dependent relaxation induced by chemical agonists acetylcholine and bradykinin has been documented in resistance vessels. However, the contribution of residual NO to the vasodilatation in response to pressure and fluid shear stress is not well understood. In this study, to demonstrate the activity of residual NO, we applied a NO scavenger, hydroxocobalamin (HCX), on the phenylephrine-induced increase in perfusion pressure in the presence of NOS inhibitors, Nω-nitro-L-arginine (L-NA) or Nω-nitro-L-arginine methyl ester (L-NAME) in the rat perfused mesenteric bed. The perfusion pressure was increased by phenylephrine (1-2 µM), an α1-adrenoceptor agonist. This increase was augmented by the addition of L-NA or L-NAME. In the presence of any NOS inhibitors, the application of hydroxocobalamin (100 µM) further increased the perfusion pressure. The removal of endothelium by saponin (50 mg/L) and the use of a non-selective protein kinase inhibitor, staurosporine (5 nM), and a tyrosine kinase inhibitor, erbstatin A (30 µM), but not a calmodulin inhibitor, calmidazolium (0.5 µM), inhibited the additional pressor responses induced by L-NA or L-NAME and a combination of either of them with hydroxocobalamine. These findings show that there could be a NOS inhibitor-resistant residual NO production in response to pressure in the rat mesenteric vascular bed. This residual NO production may be associated with the activation of tyrosine kinase and protein kinases, but not calmodulin. Finally, this pressure-induced residual NO exerts a modulatory role against vasoconstriction induced by phenylephrine.

Do cholinergic nerves innervating rat mesenteric arteries regulate vascular tone?

Vascular blood vessels have various types of cholinergic acetylcholine receptors (AChR), but the source of ACh has not been confirmed. Perivascular adrenergic nerves and nonadrenergic calcitonin gene-related peptide (CGRP)-containing (CGRPergic) nerves innervate rat mesenteric arteries and regulate vascular tone. However, function of cholinergic innervation remains unknown. The present study investigated cholinergic innervation by examining effects of cholinesterase inhibitor (neostigmine), a muscarinic AChR antagonist (atropine), and a nicotinic AChR antagonist (hexamethonium) on adrenergic nerve-mediated vasoconstriction and CGRPergic nerve-mediated vasodilation in rat mesenteric vascular beds without endothelium. In preparations treated with capsaicin (CGRP depletor) or in the presence of N(ω)-nitro-l-arginine methyl ester (nonselective nitric oxide synthase inhibitor), perivascular nerve stimulation (PNS; 2-12 Hz) evoked a frequency-dependent vasoconstriction. In the same preparations, exogenous norepinephrine induced a concentration-dependent vasoconstriction. Atropine, hexamethonium, and neostigmine had no effect on vasoconstrictor responses to PNS and norepinephrine injections. In denuded preparations, these cholinergic agents did not affect the PNS (12 Hz)-evoked release of norepinephrine in perfusate. In preconstricted preparations without endothelium in the presence of guanethidine (adrenergic neuron blocker), PNS (1-4 Hz) induced a frequency-dependent vasodilation, which was not affected by atropine, hexamethonium, and neostigmine. In denuded preparations treated with capsaicin and guanethidine, PNS did not induce vascular responses, and atropine, neostigmine, and physostigmine had no effect on PNS. Immunohistochemistry study showed choline acetyltransferase-immunopositive fibers, which were resistant to capsaicin and 6-hydroxydopamine (adrenergic toxin). These results suggest that rat mesenteric arteries have cholinergic innervation, which is different from adrenergic and capsaicin-sensitive nerves and not associated with vascular tone regulation.

The role of endothelium in the vasorelaxant effects of the essential oil of Ocimum gratissimum in aorta and mesenteric vascular bed of rats

This study investigated the endothelium-dependent vasorelaxant effects of the essential oil of Ocimum gratissimum (EOOG) in aortas and mesenteric vascular beds isolated from rats. EOOG (3-300 µg/mL) relaxed the tonic contractions induced by phenylephrine (0.1 µmol/L) in isolated aortas in a concentration-dependent manner in both endothelium-containing and endothelium-denuded preparations. This effect was partially reversed by L-NAME (100 µmol/L) but not by indomethacin (10 µmol/L) or TEA (5 mmol/L). In mesenteric vascular beds, bolus injections of EOOG (30, 50, 100, and 300 ng) decreased the perfusion pressure induced by noradrenaline (6 µmol/L) in endothelium-intact preparations but not in those treated with deoxycholate. L-NAME (300 µmol/L) but not TEA (1 mmol/L) or indomethacin (3 µmol/L) significantly reduced the vasodilatory response to EOOG at all of the doses tested. Our data showed that EOOG exerts a dose-dependent vasodilatory response in the resistance blood vessels of rat mesenteric vascular beds and in the capacitance blood vessel, the rat aorta. This action is completely dependent on endothelial nitric oxide (NO) release in the mesenteric vascular beds but only partially dependent on NO in the aorta. These novel effects of EOOG highlight interesting differences between resistance and capacitance blood vessels.

Involvement of perivascular nerves and transient receptor potential vanilloid 1 (TRPV1) in vascular responses to histamine in rat mesenteric resistance arteries

A previous report showed that histamine in denuded mesenteric vascular beds produced a triphasic response; an initial small histamine H2 receptor-mediated vasodilation, a transient histamine H1 receptor-mediated vasoconstriction, and finally a long-lasting vasodilation. We further investigated the vascular effect of histamine in mesenteric preparations without an endothelium to clarify the possible involvement of perivascular nerves. Male Wistar rat mesenteric vascular beds without an endothelium were perfused with Krebs solution containing methoxamine to produce active tone and lafutidine to block histamine H2 receptor-mediated vasodilation. Histamine (1–100μM) was perfused for 1min and perfusion pressure was measured with a pressure transducer. Histamine caused a biphasic vascular response; initial vasoconstriction followed vasodilation. Tetrodotoxin (a neurotoxin, 1μM) and procaine (a local anesthetic, 100μM) significantly inhibited the vasoconstriction and vasodilation. Ruthenium red (a transient receptor potential vanilloid 1 (TRPV1) antagonist, 1μM) also significantly inhibited both phases of the response. Pretreatment with capsaicin (a depletor of calcitonin gene-related peptide (CGRP)-containing nerves, 5μM) significantly inhibited the vasodilation without affecting the initial vasoconstriction. Both indomethacin (a cyclooxygenase inhibitor, 0.5μM) and seratrodast (a thromboxane A2 receptor antagonist, 0.1μM) abolished the histamine-induced vasoconstriction and subsequent vasodilation. These results suggest that histamine-induced vasoconstriction and long-lasting vasodilation are mediated by activation of TRPV1 on capsaicin-sensitive and capsaicin-insensitive nerves. They also suggest that perivascular nerves and prostanoids, probably thromboxane A2, are responsible for the vascular response to histamine.

Anandamide Induces Endothelium-Dependent Vasoconstriction and CGRPergic Nerve–Mediated Vasodilatation in the Rat Mesenteric Vascular Bed

An endogenous cannabinoid anandamide (N-arachidonoylethanolamide) has been shown to cause vasodilatation in vitro and a brief vasoconstriction followed by prolonged depressor response in vivo. This study investigated the vascular effects of anandamide and underlying mechanisms in rat mesenteric vascular beds. In preparations with an intact endothelium and active tone, anandamide at low concentrations (0.1 – 1 nM) caused a concentration-dependent decrease in perfusion pressure due to vasodilatation, but at high concentrations (10 nM – 1 μM) elicited an initial and sharp increase in perfusion pressure due to vasoconstriction followed by long-lasting vasodilatation in a concentration-dependent manner. Treatment with SR141716A [cannabinoid-1 (CB1)-receptor antagonist] blunted both the vasoconstrictor and vasodilator responses. Also, removal of the endothelium and indomethacin (cyclooxygenase inhibitor), but not adrenergic denervation with 6-hydoxydopamine (adrenergic neurotoxin), markedly inhibited the vasoconstrictor response to anandamide, while these treatments did not affect vasodilatation. The vasodilatation, but not vasoconstriction, in response to anandamide was markedly attenuated by capsazepine [selective antagonist for transient receptor potential vanilloid-1 (TRPV1)], pretreatment with capsaicin [calcitonin gene–related peptide (CGRP)ergic-nerve depletor], or cold-storage denervation. These results suggest that in rat mesenteric vascular beds, anandamide causes CB1-receptor–and prostanoid-mediated endothelium-dependent vasoconstriction and perivascular capsaicin-sensitive CGRPergic nerve–mediated vasodilatation.

Endothelium-Derived Relaxing Factor–Mediated Vasodilation in Mouse Mesenteric Vascular Beds

The endothelium in rat mesenteric vascular beds has been demonstrated to regulate vascular tone by releasing mainly endothelium-derived hyperpolarizing factor (EDHF), which is involved in the activation of K+ channels and gap-junctions. However, it is unclear whether the endothelial system in mouse resistance arteries contributes to regulation of the vascular tone. The present study was designed to investigate the role of the endothelium using acetylcholine and A23187 (Ca2+ ionophore) in mesenteric vascular beds isolated from male C57BL/6 mice and perfused with Krebs solution to measure perfusion pressure. In preparations with active tone produced by methoxamine in the presence of guanethidine, injections of acetylcholine, A23187, and sodium nitroprusside (SNP) caused a concentration-dependent decrease in perfusion pressure due to vasodilation. The vasodilator responses to acetylcholine and A23187, but not SNP, were abolished by endothelium dysfunction and significantly inhibited by Nω-nitro-l-arginine methyl ester (nitric oxide synthase inhibitor) and tetraethylammonium (K+-channel inhibitor) but not glibenclamide (ATP-sensitive K+-channel inhibitor). Indomethacin (cyclooxygenase inhibitor) significantly blunted only A23187-induced vasodilation, while 18α-glycyrrhetinic acid (gap-junction inhibitor) attenuated only acetylcholine-induced vasodilation. These results suggest that the endothelium in mouse mesenteric arteries regulates vascular tone by prostanoids, EDHF, and partially by nitric oxide, different from the endothelium of rat mesenteric arteries.

Adrenergic Stimulation–Released Histamine Taken-up in Adrenergic Nerves Induces Endothelium-Dependent Vasodilation in Rat Mesenteric Resistance Arteries

The present study investigated whether histamine was taken up by perivascular adrenergic nerves and released by periarterial nerve stimulation (PNS) to induce vascular responses. In rat mesenteric vascular beds treated with capsaicin to eliminate calcitonin gene–related peptide (CGRP)ergic vasodilation and with active tone, PNS (1 – 4 Hz) induced only adrenergic nerve–mediated vasoconstriction. Histamine treatment for 20 min induced PNS-induced vasoconstriction followed by vasodilation without affecting CGRP-induced vasodilation. Chlorpheniramine, guanethidine, combination of histamine and desipramine, and endothelium-removal abolished PNS-induced vasodilation in histamine-treated preparations. These results suggest that histamine taken up by and released from adrenergic nerves by PNS causes endothelium-dependent vasodilation in rat mesenteric arteries.

Mg2+-induced adenosine-receptor mediated relaxations in mesenteric vascular beds of diabetic rats

Our previous studies showed that the magnesium Mg2+-induced relaxations were completely dependent on concentration of nitric oxide (NO) in non-diabetic rat mesenteric vascular beds, in diabetic rats other mechanisms may be involved. The present study was designed to determine the role of adenosine receptor in Mg2+-induced relaxation in streptozotocin (STZ)-induced diabetic rats vessels. Diabetes was induced by the intravenous injection of 60 mg/kg STZ. Eight weeks after diabetes induction, superior mesenteric arteries were isolated and perfused according to the McGregor method. Prepared vascular beds were constricted with phenylephrine to induce 70-75% of maximal constriction (0.001 M). Mg2+ at concentrations of 10(-4) to 10(-1) M were added into the medium and perfusion pressure was recorded. Theophylline (1 mM), and 3,7- dimethyl-1- propargylxanthine (0.01 μM) were added into medium 20 min before phenylephrine administration. In the presence of theophylline, vasorelaxation induced by high dose of Mg2+ (from 0.03 to 0.1 M) was totally suppressed. In presence of N(ω)-nitro-L-arginine methyl ester (L-NAME), the response of Mg2+ was completely inhibited at low dose of Mg2+. But, Mg2+-induced relaxation in the presence of adenosine A2a receptor blocker was significantly suppressed in high dose of Mg2+. Mg2+-induced relaxation in the presence of an A2a receptor blocker was not suppressed either by denudation of endothelium or presence of L-NAME. From the results of this study it may be concluded that Mg2+-induced relaxation at high concentrations is mediated by adenosine A2a receptors, but at low concentrations Mg2+-induced relaxation is dependent on NO.

Vascular deconjugation of quercetin glucuronide: The flavonoid paradox revealed?

The dietary flavonoid quercetin exerts protective cardiovascular effects. Because quercetin is rapidly metabolized into less active or inactive glucuronidated metabolites and the plasma concentrations of free quercetin are very low, a huge amount of scientific data generated along decades with the unconjugated compounds in vitro has been questioned. We aimed to determine whether glucuronidated quercetin can deconjugate in situ and whether deconjugation leads to a biological effect. Quercetin and quercetin-3-O-glucuronide (Q3GA) were perfused through the isolated rat mesenteric vascular bed. Quercetin was rapidly metabolized in the mesentery. In contrast, the decay of Q3GA was slower and was accompanied by a progressive increase of quercetin in the perfusate and in the tissue over 6 h, which was prevented by the β-glucuronidase inhibitor saccharolactone. Incubation of mesenteric arterial rings mounted in a wire myograph with Q3GA for ≥1 h resulted in a significant inhibition of the contractile response which was also prevented by saccharolactone. Moreover, the intravenous administration of Q3GA resulted in a slow onset and sustained blood pressure lowering effect, demonstrating for the first time that Q3GA has effects in vivo. We propose that Q3GA behaves as a quercetin carrier in plasma, which deconjugates in situ releasing the aglycone which is the final effector.

Ingestion of (n-3) Fatty Acids Augments Basal and Platelet Activating Factor-Induced Permeability to Dextran in the Rat Mesenteric Vascular Bed

AbstractLoss of intestinal barrier function and subsequent edema formation remains a serious clinical problem leading to hypoperfusion, anastomotic leakage, bacterial translocation, and inflammatory mediator liberation. The inflammatory mediator platelet activating factor (PAF) promotes eicosanoid-mediated edema formation and vasoconstriction. Fish oil-derived (n-3) fatty acids (FA) favor the production of less injurious eicosanoids but may also increase intestinal paracellular permeability. We hypothesized that dietary (n-3) FA would ameliorate PAF-induced vasoconstriction and enhance vascular leakage of dextran tracers. Rats were fed either an (n-3) FA-rich diet (EPA-rich diet; 4.0 g/kg EPA, 2.8 g/kg DHA) or a control diet (CON diet; 0.0 g/kg EPA and DHA) for 3 wk. Subsequently, isolated and perfused small intestines were stimulated with PAF and arterial pressure and the translocation of fluid and macromolecules from the vasculature to lumen and lymphatics were analyzed. In intestines of rats fed the EPA-rich diet, intestinal phospholipids contained up to 470% more EPA and DHA at the expense of arachidonic acid (AA). The PAF-induced increase in arterial pressure was not affected by the EPA-rich diet. However, PAF-induced fluid loss from the vascular perfusate was higher in intestines of rats fed the EPA-rich diet. This was accompanied by a greater basal loss of dextran from the vascular perfusate and a higher PAF-induced transfer of dextran from the vasculature to the lumen (P = 0.058) and lymphatics. Our data suggest that augmented intestinal barrier permeability to fluid and macromolecules is a possible side effect of (n-3) FA-rich diet supplementation.

P.1.c.035 Social isolation induces changes in BDNF, Arc protein and dendritic spines density: reversal by social housing

Using a number of agonist and antagonist compounds, we attempted to characterize the responses and receptors involved in the effects of 5-hydroxytryptamine (5-HT) in the in situ blood perfused rat mesentery. An intra-arterial (i.a.) bolus injection of 5-HT increased mesenteric perfusion pressure in a dose-dependent way but did not change the systemic blood pressure. The selective 5-HT2 receptor agonists α-methyl-5-HT, 1-(3-chlorophenyl)piperazine dihydrochloride (m-CPP) and (±)-1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane hydrochloride (DOI), caused a local vasoconstrictor effect in the autoperfused vascular mesenteric bed. Intra-arterial injection of 5-carboxamidotryptamine (5-CT) and 1-(m-chlorophenyl)-biguanide (m-CPBG) did not modify the mesenteric perfusion pressure. The vasoconstrictor effect elicited by 5-HT and α-methyl-5-HT was significantly decreased by ritanserin and by a selective 5-HT2B/2C receptor antagonist, N-3-pyridinyl-3,5-dihydro-5-methyl-benzo[1,2-b:4,5-b′]dipyrrole-1(2H)-carboxamide hydrochloride (SB 206553), but was not modified by prazosin, propranolol, indomethacin or enalapril pretreatment. Our data suggest that the vasoconstrictor serotonergic response induced in the in situ autoperfused rat mesenteric vascular bed is mainly mediated by activation of 5-HT2B and/or 5-HT2C receptors.