Intact Aortic Rings Research Articles

Abstract P453: Dissecting tunica responsibility in arterial stress relaxation: Smooth muscle need not apply

Perivascular adipose tissue (PVAT) is being recognized as an important arterial tunica. Stress relaxation, a gradual reduction in stress over time while under a constant strain, is considered a property of smooth muscle (ex. intestine, uterus, bladder). While aortic PVAT (aPVAT) contains a microvasculature, it does not contain organized smooth muscle and isolated PVAT stress relaxes to a greater extent than the vessel itself. This raised the idea that other tunicas lacking smooth muscle may also stress relax. Here we hypothesize that appropriately oriented and functional smooth muscle was not necessary for stress relaxation to occur. To test this, we used histochemical staining and isometric contractility of thoracic aorta from the male Dahl salt-sensitive (SS) rat. Some rings of aorta were separated into adventitia (no muscle), media (muscle), and PVAT (no muscle), and responses of these isolates compared to the intact aortic ring (muscle + integration of tunicas). Masson Trichrome (MT) and Verhoeff Van Gieson (VVG) staining validated the dissection of the different tunicas with minimal contamination of cells from other tunicas. Stress relaxation was measured after increasing, cumulative amounts of passive tension (6 grams total) was applied in the presence or absence of Ca 2+ , essential for smooth muscle contraction. Each step was followed by challenge with a maximum concentration of the a 1 adrenergic agonist phenylephrine (PE, 10 -5 M). Stress relaxation occurred in all tunicas at each passive tension, whether or not Ca 2+ was present (figures). In fact, loss of Ca 2+ improved stress relaxation in adventitia and PVAT. Importantly, in the presence of Ca 2+ , PE contraction was observed at each passive tension in tissues containing smooth muscle: media (min, 250 mg PT: 26.67 +/- 8.51 mg; max, 6000 mg PT: 589.59 +/- 114.53 mg) and aorta + PVAT (min, 250 mg PT: 562.61 +/- 238.45 mg; max, 6000 mg PT: 1322.91 +/- 352.73mg). Little to no measurable contraction was recorded in the adventitia and aPVAT. There was little to no measurable contraction in tunicas in the absence of Ca 2+ . Taken together, these data suggest that all tunicas of the rat thoracic aorta stress relax and can do so without the presence of organized smooth muscle. Of all tunicas, PVAT demonstrated the greatest ability to stress relax. Collectively, these findings force reconsideration of individual responsibilities of arterial tunicas, all of which participate in the (dys)function of an artery.

Chemical Characterization of Phoenix dactylifera L. Seeds and their Beneficial Effects on the Vascular Response in Hypertensive Rats.

Although Phoenix dactylifera dates are traditionally consumed for their health benefits, no research has been done on the vascular response in hypertensive animals. This study evaluated the vascular relaxation of hydroalcoholic extracts from seeds of three varieties of P. dactylifera; Sukkari seed (SS), Ajwa seed (AS), and Mabroom seed (MS) on L-NAME-induced hypertension and spontaneously hypertensive rats (SHR). Results showed that all extracts (10µg/mL) caused relaxations higher than 60% in the aortic rings precontracted with 10- 6 M phenylephrine in normotensive rats, the SS extract was the most potent. Endothelial nitric oxide (NO) pathway is involved as significantly reduced vascular relaxation in denuded-endothelium rat aorta and with an inhibitor (10- 4 M L-Nω-Nitro arginine methyl ester; L-NAME) of endothelial nitric oxide synthase (eNOS). Confocal microscopy confirmed that 10µg/mL SS extract increases NO generation as detected by DAF-FM fluorescence in intact aortic rings. Consistent with these findings, vascular relaxation in intact aortic rings at 10µg/mL SS extract was significantly decreased in L-NAME-induced hypertensive rats (endothelial dysfunction model), but not in SHR. In both hypertensive models, the denuded endothelium blunted the vascular relaxation. In conclusion, the hydroalcoholic extract of the seed of P. dactylifera (Sukkari, Ajwa and Mabroom varieties) presents a potent endothelium-dependent vascular relaxation, via NO, in normotensive rats as well as in two different models of hypertension. This effect could be mediated by the presence of phenolic compounds identified by UHPLC-ESI-MS/MS, such as protocatechuic acid, and caftaric acid.

Elsholtzia ciliata Essential Oil Exhibits a Smooth Muscle Relaxant Effect.

A recent in vivo study in pigs demonstrated the hypotensive properties of essential oil extracted from the blossoming plant Elsholtzia ciliata. This study was designed to examine the effect of E. ciliata essential oil (EO) on smooth muscle contraction. Tension measurements were performed on prostate strips and intact aortic rings isolated from rats. Results showed that EO caused a concentration-dependent reduction in phenylephrine-induced contraction of both the prostate and aorta, with a more pronounced inhibitory effect in the prostate. The IC50 of EO for the prostate was 0.24 ± 0.03 µL/mL (n = 10) and for the aorta was 0.72 ± 0.11 µL/mL (n = 4, p < 0.05 vs. prostate). The chromatographic analysis identified elsholtzia ketone (10.64%) and dehydroelsholtzia ketone (86.23%) as the predominant compounds in the tested EO. Since both compounds feature a furan ring within their molecular structure, other furan ring-containing compounds, 2-acetylfuran (2AF) and 5-methylfurfural (5MFF), were examined. For the first time, our study demonstrated the relaxant effects of 2AF and 5MFF on smooth muscles. Further, results showed that EO, 2AF, and 5MFF altered the responsiveness of prostate smooth muscle cells to phenylephrine. Under control conditions, the EC50 of phenylephrine was 0.18 ± 0.03 µM (n = 5), while in the presence of EO, 2AF, or 5MFF, the EC50 values were 0.81 ± 0.3 µM (n = 5), 0.89 ± 0.11 µM (n = 5), and 0.69 ± 0.23 µM (n = 4), respectively, p < 0.05 vs. control. Analysis of the affinity of EO for α1-adrenergic receptors in the prostate suggested that EO at a certain range of concentrations has a competitive antagonistic effect on α1-adrenergic receptors. In conclusion, EO elicits a relaxant effect on smooth muscles which may be related to the inhibition of α1-adrenoreceptors.

Extract of Chenopodium album lowers blood pressure in rats through endothelium-dependent and -independent vasorelaxation

To investigate the antihypertensive effect of crude extract of Chenopodium album (Ca.Cr), based on its medicinal use in hypertension. Ca.Cr and its fractions were tested in-vivo in normotensive anesthetized rats for blood pressure-lowering effect. In-vitro experiments were performed on isolated rat aortae to explore the vascular mechanism(s). In normotensive anesthetized rats, Ca.Cr produced a dose-dependent (1-300mg/kg) fall (30%mmHg) in mean arterial pressure (MAP). Among the fractions, nHexane was the most potent (46% fall). In rat aortic rings precontracted with phenylephrine (PE), Ca.Cr and its fractions (except Ca.Aq) produced endothelium-dependent vasorelaxation, which was partially reversed with endothelium removal and by pretreating intact aortic rings with L-NAME (10μM) and atropine (1μM). This relaxation to Ca.Cr and fractions (nHexane, ethylacetate and chloroform) was also eliminated with indomethacin pretreatment, however, it unmasked a vasoconstriction effect with Ca.Cr only. Surprisingly, the aqueous fraction produced a calcium sensitive strong vasoconstriction instead of vasorelaxation. The crude extract and its fractions (except Ca.Aq) also antagonized vasoconstriction induced with high K+ (80mM), suggesting calcium antagonistic effect. The aqueous fraction produced mild vasorelaxation against high K+. This effect was further confirmed when pretreatment of the aortic rings with different concentrations of crude extract and fractions suppressed CaCl2 concentration response curves, similar to verapamil. In acute toxicity test, Ca.Cr extract was found safe up to 5g/kg body weight in mice. These findings suggest that crude extract and fractions of C.album produced vasorelaxant effect through muscarinic receptors linked-NO pathway, prostaglandin (endothelium-dependent) and calcium antagonism (endothelium-independent), which explains the blood pressure lowering effect of C.album in rats.

Release of 6-nitrodopamine modulates vascular reactivity of Pantherophis guttatus aortic rings

6-Nitrodopamine (6-ND) is a novel catecholamine that is released from human umbilical cord vessels and Chelonoidis carbonaria aortic rings. The synthesis/release of 6-ND is inhibited by either pre-incubation of the vessels with the nitric oxide (NO) synthase inhibitor L-NAME or by mechanical removal of the endothelium. 6-ND causes powerful vasorelaxation, acting as a potent and selective dopamine D2-like receptor antagonist.Basal release of 6-ND from Panterophis guttatus endothelium intact and denuded aortic rings was quantified by LC-MS/MS. In order to evaluate the interaction of 6-ND with other catecholamines, aortic rings were suspended vertically between two metal hooks in 10-mL organ baths containing Krebs-Henseleit's solution and attached to isometric transducers.Endothelium intact aortic rings presented basal release of 6-ND, which was significantly reduced by previous incubation with L-NAME (100 μM). In endothelin-1 (3 nM) pre-contracted endothelium intact aortic rings, 6-ND (10pM-1 μM) and the dopamine D2-receptor antagonist L-761,626 (10 pM–1 μM) induced concentration-dependent relaxations, which were not affected by incubation with L-NAME but greatly reduced in endothelium-removed aortic rings.6-ND (0.1–1 μM) produced significant rightward shifts of the concentration-response curves to dopamine in L-NAME pre-treated endothelium-intact (pA2 7.01) rings. Contractions induced by noradrenaline and adrenaline were not affected by pre-incubation with 6-ND (1 μM). The EFS-induced contractions of L-NAME pre-treated endothelium-intact aortic rings were significantly inhibited by incubation with 6-ND (1 μM).The results indicate that 6-ND released from Pantherophis guttatus aortic rings is coupled to NO release and represents a new mechanism by which NO can modulate vascular reactivity independently of cGMP production.

VASORELAXANT MECHANISM(S) OF CLERODENDRUM VOLUBILE ETHANOL LEAF EXTRACT IN NORMAL AND DOXORUBICIN-TREATED ENDOTHELIUM INTACT AORTIC RINGS

Objectives: Doxorubicin (DOX) is a highly effective antibiotics anthracycline cytotoxic agent with a broad spectrum of activity in the treatment of solid and hematological malignancies. However, DOX is notorious for inducing cardiotoxicity and vascular dysfunction as its common off-target side effects. This study evaluated the possible vasorelaxant activity and mechanism(s) of action of Clerodendrum volubile ethanol leaf extract (CVE) in normal and DOX-pretreated endothelium intact aortic rings in Physiological Salt Solution (PSS) in vitro. Methods: The responses were recorded isometrically by an organ bath connected to Data Capsule Acquisition System. Effects of CVE on phenylephrine-precontracted endothelium intact rat aortic rings and the influence of the respective blockers for adrenergic, cholinergic, calcium channel, and prostacyclin receptors were investigated to unveil the possible underlying vasorelaxant mechanism(s) of CVE. Results: Our findings showed that CVE significantly induced vasorelaxation in phenylephrine hydrochloride (PE) and KCl precontracted endothelium intact aortic rings in a concentration-dependent manner. Furthermore, the CVE-induced vasorelaxation in PE- and KCl-precontracted aortic rings were inhibited by pre-incubation with atropine and indomethacin indicating that the vasorelaxant effect of CVE was profoundly mediated through cholinergic and prostacyclin mechanisms. Conclusion: Overall, results of this study report for the first time the vasorelaxant effect of CVE in isolated endothelium-intact doxorubicin-treated aortic rings of normotensive rats which was probably cholinergic and prostacyclin-mediated. Thus, results of this study provide further insight into the cardioprotective mechanism of CVE in doxorubicin-induced cardiotoxicity beyond the antioxidant and anti-apoptosis mechanisms that have been previously reported.

6-Nitrodopamine is an endogenous selective dopamine receptor antagonist in Chelonoidis carbonaria aorta

Chelonoidis carbonaria aortic rings present endothelium-derived release of dopamine, noradrenaline, adrenaline and 6-nitrodopamine (6-ND). Here it was investigated whether 6-ND release is coupled to nitric oxide (NO) synthesis and its action on the vascular smooth muscle reactivity.Basal release of 6-ND from aortic rings in the absence and presence of the NO synthesis inhibitor L-NAME was quantified by LC-MS-MS. Aortic rings were suspended vertically between two metal hooks in 10-mL organ baths containing Krebs-Henseleit's solution and attached to isometric transducers. The tissues were allowed to equilibrate for 1 h before starting the experiments.The release of 6-ND was significantly reduced by previous incubation with L-NAME. 6-ND (up to 300 μM) had no contractile activity in the aortic rings. 6-ND (1, 3 and 10 μM) produced significant rightward shifts of the concentration-response curves to dopamine in endothelium-intact (pA2 6.09) and L-NAME pre-treated endothelium-intact (pA2 7.06) aortic rings. Contractions induced by noradrenaline and adrenaline were not affected by pre-incubation with 6-ND. The EFS (16 Hz)-induced aortic contractions were significantly inhibited by incubation with 6-ND (10 μM).In the thromboxane A2 mimetic U-46619 (30 nM) pre-contracted endothelium intact aortic rings, 6-ND (1 nM–1 μM) and the dopamine D2-receptor antagonist haloperidol (1 nM-1 μM) induced concentration-dependent relaxations. The relaxations were not present in endothelium-removed aortic rings but they were not affected by incubation with L-NAME in endothelium-intact aortic rings.The results indicate that the synthesis of this novel catecholamine in Chelonoidis carbonaria aortic rings is coupled to NO release and that 6-ND acts as a highly selective dopamine D2-like receptor antagonist.

Vasorelaxant effect of curcubisabolanin A isolated from Curcuma longa through the PI3K/Akt/eNOS signaling pathway

Ethnopharmacological relevanceCurcuma longa L. (Zingiberaceae) is a known blood-activating and stasis-removing traditional Chinese medicine and has relevant pharmacological properties. The rhizomes of C. longa have been used for the treatment of cardiovascular disease (CVD) in China. Previous studies have shown that sesquiterpenoids from C. longa have significant vasorelaxant effects, which are closely associated with the prevention and treatment of CVD. Aim of the studyTo explore the sesquiterpenoids with vasorelaxant effects from C. longa and investigate the underlying mechanisms. Materials and methodsThe compound was isolated from C. longa by multiple chromatography technologies. Its structure was determined by extensive spectroscopic analyses, nuclear magnetic resonance (NMR) data calculations, electronic circular dichroism (ECD) data calculations, and optical rotation (OR) data calculations. The vasorelaxant effect of the isolated compound was evaluated by KCl- or phenylephrine (PHE)-inducing contraction of the rat thoracic aortic rings. Endothelial removal and L-NAME pretreatment experiments were used to verify the endothelium-dependent vasorelaxant effect of the isolated compound in rat thoracic aortic rings. NO production was monitored in human umbilical vein endothelial cells (HUVECs). Western blot was carried out in HUVECs to elucidate the potential mechanisms. ResultsA new bisabolane-type sesquiterpenoid, curcubisabolanin A [(+)-(1S,7S,9E)-bisabola-2(3),4(15),9(10)-trien-11-ol], was isolated from the rhizomes of C. longa. curcubisabolanin A exhibited endothelium-dependent relaxation on rat thoracic aortic rings, while pre-treatment of intact aortic rings with an eNOS inhibitor (L-NAME) attenuated the vasorelaxant response of curcubisabolanin A. In addition, curcubisabolanin A induced intracellular NO production and significantly increased the levels of phosphorylated PI3K (p-PI3K), phosphorylated Akt (p-Akt), and phosphorylated eNOS (p-eNOS) in HUVECs. LY294002 (a blocker of PI3K) and MK-2206 (a highly selective inhibitor of Akt) significantly decreased these effects of curcubisabolanin A. ConclusionsThese findings demonstrated that the vasorelaxant effect of curcubisabolanin A was partially endothelium-dependent and was related to regulation of NO production in vascular endothelial cells through the PI3K/Akt/eNOS signaling pathway.

Insight into the cardiovascular mechanisms of blood pressure lowering effect of gitogenin: a steroidal saponin

ABSTRACT Background/objectives : Steroidal saponins are widely distributed in medicinal plants with potential applications in cardiovascular disorders. Gitogenin, a saponin, has not been explored as antihypertensive; this investigation was aimed to explore its blood pressure lowering potential and underlying mechanisms. Methodology : The effect of gitogenin was evaluated on blood pressure in vivo, using normotensive rat model and the underlying cardiovascular mechanism(s) in vitro, in isolated rat aorta and in atria preparations using PowerLab data acquisition system (ADInstrument, Australia). Results : Intravenous injection of gitogenin decreased mean arterial pressure (MAP) in anesthetized rats. Atropine (1 mg/kg) and L-NAME (100 mg/kg) pretreatment significantly (*p < .05) attenuated effect on MAP to gitogenin. In isolated intact aortic rings, gitogenin induced endothelium-dependent vasodilatation (maximum 65%), which was ablated (maximum 22%) with L-NAME (100 mg/kg) and atropine (1 μM) pretreatment or endothelium removal. Gitogenin was found more potent against angiotensin II precontractions without effect on high K+ and low K+ precontractions. In isolated rat right atria, gitogenin suppressed rate and force of contractions. Atropine (1 μM) pretreatment partially inhibited effect of gitogenin on force and eliminated its effect on rate. Combined atropine (10 μM) and atenolol (0.5 μM) pretreatment was without effect on force of contractions but eliminated effect of gitogenin on rate with 25% increase. Conclusion : These findings indicate that antihypertensive effect of gitogenin is the outcome of vascular and cardiac effects; agonistic effect on vascular M3 and cardiac M2 receptors; and being more selective for M2. Increase in the rate of atrial contraction might be of clinical importance.

Effects of oleuropein on rat's atria and thoracic aorta: a study of antihypertensive mechanisms.

Oleuropein (OLE) is the main bioactive ingredient in the leaves of the olive plant Olea europaea L. (Oleaceae), which has proven beneficial due to the antiinflammatory, antiatherogenic, anticancer, antimicrobial, and antiviral effects. This study aimed to investigate the antihypertensive and vasodilator potential of OLE by analyzing its acute effects on spontaneous atrial contractions and vasomotor responses of the isolated thoracic aorta in rats. We showed that the application of OLE induces negative chronotropic and inotropic effects on the heart. OLE also causes mild aortic vasodilation given that the maximal reduction in tension of intact aortic rings precontracted with phenylephrine was approximately 30%. This vasodilation is likely dependent on the nitric oxide released from the endothelium based on the effect obtained on denuded and phenylephrine precontracted aortic rings and responses reordered following vasoconstriction induced by high concentrations of K+ and heparin. Our findings provide a basis for further testing of OLE cardiovascular effects, which may lead to subsequent clinical research for its application in the treatment of hypertension and heart disease.

The hypertensive effect of sorafenib is abolished by sildenafil

BackgroundContrasting to the well documented tyrosine kinase inhibitor (TKI)-induced hypertension, little is known on their intrinsic vasomotor effects. We investigated the vasomotor effects of sorafenib, a widely used multikinase inhibitor in the treatment of hepatocellular and renal cell carcinoma and tested the hypothesis that sildenafil, a phosphodiesterase-5 (PDE-5) inhibitor, could represent a pharmacological strategy for the treatment of TKI-induced hypertension.MethodsConcentration-response curves of sorafenib were constructed in endothelium-intact or denuded precontracted rat aorta, in the presence or absence of several inhibitors. Acute intravenous effects of sorafenib on arterial blood pressure were also investigated in anaesthetized rats. Finally, rats were chronically treated with sorafenib during 4 weeks in the presence and absence of sildenafil.ResultsIn endothelium intact aortic ring, sorafenib induced a potent concentration-dependent relaxation of precontracted rat aorta. Removal of the endothelium shifted the concentration-response curve of sorafenib to the right and significantly reduced its maximal effects, demonstrating that sorafenib-induced vasorelaxation is endothelium-dependent and endothelium-independent. Inhibition of the different pathways implicated in the endothelium-dependent and independent vasorelaxation revealed that the endothelium-dependent effects of sorafenib result mainly from the activation of prostaglandin and the nitric oxide (NO) pathways. The endothelium-independent vasodilatory effects of sorafenib may result mainly from the activation of Na/K-ATPase and soluble guanylate cyclase. These vasodilatory effects observed in vitro were confirmed by the decrease in arterial blood pressure observed during acute administrations of sorafenib in anesthetized rats. Finally, and most importantly, we report here for the first time that chronic administration of sorafenib in rats induced an increase in SBP that was abolished by sildenafil.ConclusionThe multikinase inhibitor sorafenib induced in vitro vasorelaxation of large conductance artery, primary by activating soluble guanylate cyclase. Its chronic administration led to arterial blood hypertension that was counteracted by a PDE-5 inhibitor, sildenafil. Our results suggest that targeting the cGMP pathway including NO signalling might be an interesting pharmacological strategy for the treatment of TKI-induced hypertension.

Vaso‐relaxant Effect of Zingiber officinale Extract Involves Release of Nitric Oxide from the Endothelium

IntroductionZingiber officinale (ZO) is an important plant with several medicinal, nutritional and ethnomedical values. The blood pressure lowering effect of ZO has been reported in experimental animals and human and some mechanisms have been postulated, including; blockage of voltage dependent calcium channel, stimulation of muscarinic receptors and serotonergic antagonistic property. The aim of this study is to investigate the vaso‐relaxant effect of the extract of ZO and the mechanism by which it is produced.MethodRhizomes of ZO were extracted in 80% methanol. Thoracic aorta isolated from male rabbits were cut into rings of 3–5 mm, mounted in organ baths containing 25 ml Krebs physiological solution maintained at 37 °C and bubbled continuously with a mixture of 95% O2 and 5% CO2. The aortic rings were equilibrated for 30 min at a resting tension of 1 g. Responses were recorded isometrically via a force displacement transducer connected to a recording system. The presence of functional endothelium was checked by the ability of acetylcholine (1μM) to induce relaxation on phenylepherine (PE, 1μM) contracted rings. The relaxant responses to ZO was recorded by adding cumulative concentrations (10, 20, 40, 80, 100, 500, 1000 μg/ml) of ZO. To investigate the involvement of endothelium in the vaso‐relaxant action, endothelium was removed by gently rubbing the luminal surface of the ring with a polyethylene tube. To investigate which endothelium‐derived vasorelaxant factors were involved, the rings were pre‐incubated with Nitro‐L‐arginine methyl ester (L‐NAME, 10 μM) or indomethacin (10 μM) for 30 min before addition of the spasmogen and ZO. Relaxant responses were expressed as percentage relaxation from PE‐precontraction levels. The EC50 (the concentration required to cause half‐maximal relaxation) was calculated from the concentration‐response curve. Results were expressed as means ± s.e.m. Student t‐test was used to assess the significant differences at (p &lt; 0.05)ResultsZO produced a vaso‐relaxation effect on rings pre‐contracted with PE (1μM) at concentrations of 20–100 μg/ml in endothelium intact rings with an EC50 of 14.8±1.2 μg/ml (Figure 1). This relaxation was not however seen at 500–1000 μg/ml but rather a vaso‐contraction was observed. In endothelium denuded rings, the vaso‐relaxation effect of ZO at 20–100 μg/ml was abolished while vaso‐relaxation was observed with 500–1000 μg/ml, the concentrations that otherwise produced contraction in endothelium intact aortic rings. Pre‐incubation of the tissues with L‐NAME (10μM) abolished the relaxant effect of ZO at 20–100μg/ml but caused relaxation effect with 500–1000 μg/ml similar to that observed with endothelium denuded rings. Pretreatment with indomethacin abolished the relaxant effect of ZO at 20μg/ml but not at 40 μg/ml and above (Figure 2).ConclusionVaso‐relaxant effect of ZO is seen at lower concentrations, endothelium dependent and may involve the release of nitric oxide from the endothelium. There may be interplay between contractile and relaxant compounds in crude extract of ZO at concentrations above 500 μg/ml.Support or Funding InformationThe PhD study grant awarded to I.M Adebisi by Usmanu Danfodiyo University, Sokoto, Nigeria is acknowledgedRelaxation effect of methanol extract of Zingiber officinale (ZO) on phenylephrine‐precontracted aortic rings with intact endothelium. Data represent the mean ± s.e.m. of four individual experiments. * is p&lt;0.05Figure 1Relaxation effect of methanol extract of Zingiber officinale (ZO) on phenylephrine‐precontracted aortic rings with endothelium, without endothelium and effect of L‐NAME (10 μM), and Indomethacin (10 μM) on ZO induced vasorelaxation on phenylephrine‐precontracted aortic rings with endothelium. Data represent the mean ± s.e.m. of four individual experiments. * is p&lt;0.05Figure 2

Nandrolone combined with strenuous resistance training reduces vascular nitric oxide bioavailability and impairs endothelium-dependent vasodilation

Anabolic Androgenic Steroids (AASs) misuse has increased among adolescents and recreational athletes due to their potential effects on muscle hypertrophy. On the other hand, AAS might induce alterations on cardiovascular system, although some controversies regarding AAS on vascular properties remain unknown. To address this question, we aimed to investigate the effects of high doses of nandrolone combined with strenuous resistance training (RT) on function and structure of thoracic aorta. Rats were randomized into four groups: non-trained vehicle (NTV), trained vehicle (TV), non-trained nandrolone (NTN), and trained nandrolone (TN), and submitted to 6 weeks of treatment with nandrolone (5 mg/kg, twice a week) and/or resistance training. In vitro response of thoracic aorta to acetylcholine (ACh) was analyzed. Vascular nitric oxide (NO) and reactive oxygen species (ROS) synthesis were evaluated using 4,5-diaminofluorescein diacetate (DAF-2) and hydroethidine fluorescent techniques, respectively. Thoracic aorta was processed for microscopy analyses and tunica media thickness was measured. ACh-mediated relaxation response was impaired in endothelium intact aortic rings isolated from trained rats (TV and TN) as compared with their matched non-trained groups. TN rats showed reduced ACh-mediated vasodilatation than NTN rats. NO production and bioavailability decreased in thoracic aorta of nandrolone-treated rats in relation to their matched non-trained group (NTN vs. NTV; TN vs. TV). ROS production and tunica media thickness were increased in TN rats when compared with TV rats. These findings indicate that high doses of nandrolone combined with strenuous RT affect NO bioavailability and might induce endothelial dysfunction and arterial morphological alterations.

Ascorbate Attenuates Oxidative Stress and Increased Blood Pressure Induced by 2-(4-Hydroxyphenyl) Amino-1,4-naphthoquinone in Rats.

Quinone derivatives like 2-(4-hydroxyphenyl) amino-1,4-naphthoquinone (Q7) are used as antitumor agents usually associated with adverse effects on the cardiovascular system. The objective of this study was to evaluate the cardioprotective effect of ascorbate on Q7-induced cardiovascular response in Wistar rats. In this study, blood pressure, vascular reactivity, and intracellular calcium fluxes were evaluated in cardiomyocytes and the rat aorta. We also measured oxidative stress through lipid peroxidation (TBARS), superoxide dismutase- (SOD-) like activity, and H2O2 generation. Oral treatment of rats with ascorbate (500 mg/kg) for 20 days significantly (p < 0.05) reduced the Q7-induced increase (10 mg/kg) in blood pressure and heart rate. The preincubation with ascorbate (2 mM) significantly (p < 0.05) attenuated the irregular beating of the atrium induced by Q7 (10−5 M). In addition, ascorbate induced endothelial vasodilation in the presence of Q7 in the intact aortic rings of a rat and reduced the cytosolic calcium levels in vascular smooth muscle cells. Ascorbate also reduced the Q7-induced oxidative stress in vivo. Ascorbate also attenuated Q7-induced SOD-like activity and increased TBARS levels. These results suggest a cardioprotective effect in vivo of ascorbate in animals treated orally with a naphthoquinone derivative by a mechanism involving oxidative stress.

Role of calcium channels and endothelial factors in nickel induced aortic hypercontraction in Wistar rats.

Aim: To investigate the mechanism of nickel augmented phenylephrine (PE)-induced contraction in isolated segments of Wistar rat aorta. Materials and Methods: Effect of varying concentrations of nickel on PE-induced contraction were investigated in isolated segments of Wistar rat aorta using an organ bath system. Aortic rings were pre-incubated with verapamil (1 µM and 20 µM), gadolinium, apocynin, indomethacin or N-G-nitro-L-arginine methyl ester (L-NAME) separately before incubation with nickel. Results: Endothelium intact aortic rings incubated with 100 nM, 1 µM or 100 µM of nickel exhibited 80%, 43% and 28% increase in PE-induced contraction, respectively, while no such enhancing responses were observed in endothelium denuded aorta. Incubation of aortic rings with 1 µM and 20 µM verapamil suggested an involvement of influx of calcium through T-type calcium channels in smooth muscle cells, while aortic rings pre-incubated with gadolinium showed no role of store operated calcium channels in the nickel effect on PE-induced contractions. The enhancing effect of nickel on PE-induced contractions was inhibited by apocynin, indomethacin or L-NAME. Conclusion: Nickel has caused augmentation of PE-induced contractions as a result of the endothelial generation of reactive oxygen species (ROS) and cyclooxygenase 2 (COX2) dependent endothelium contracting factors (EDCFs), which increases the influx of extracellular calcium through T-type Ca2+ channels in smooth muscle cells.

Anti-hypertensive and vasodilatory effects of amended Banxia Baizhu Tianma Tang

Although Banxia Baizhu Tianma Tang (BBT) has been long administered for hypertensive treatment in Traditional Chinese Medicine (TCM), the ratio of the herbal components that makes up the formulation has not been optimized with respect to the anti-hypertensive effect that it inherently possesses. A newly amended BBT (ABBT) formulation was developed using the evidence-based approach of orthogonal stimulus-response compatibility model. The ABBT showed enhanced therapeutic effect while maintaining its traditional theoretical approach rooted in TCM. This study was designed to investigate the possible mechanism of actions involved in the vasodilatory activity of ABBT-50 by evaluating its vasodilative effect on isolated Sprague Dawley rats in the presence of absence of various antagonists. When pre-contracted with phenylephrine, relaxation was observed in endothelium intact (EC50=0.027±0.003mg/ml, Rmax=109.8±2.12%) and denuded aortic rings (EC50=0.409±0.073mg/ml, Rmax=63.15±1.78%), as well as in endothelium intact aortic rings pre-contracted with potassium chloride (EC50=32.7±12.16mg/ml, Rmax=34.02±3.82%). Significant decrease in the vasodilative effect of ABBT-50 was observed in the presence of Nω-nitro-l-arginine methyl ester (EC50=0.12±0.021mg/ml, Rmax=75.33±3.28%), 1H-[1,2,4] Oxadiazolo[4,3-a]quinoxalin-1-one (EC50=0.463±0.18mg/ml, Rmax=54.48±2.02%), methylene blue (EC50=0.19±0.037mg/ml, Rmax=83.69±3.19%), indomethacin (EC50=0.313±0.046mg/ml, Rmax=71.33±4.12%), atropine (EC50=0.146±0.013mg/ml, Rmax=77.2±3.41%), and 4-aminopyridine (EC50=0.045±0.008mg/ml, Rmax=95.55±2.36%). ABBT-50 was also suppressing Ca2+ release from sarcoplasmic reticulum and inhibiting calcium channels. Vasodilatory effects of ABBT-50 are mediated through NO/sGC/cGMP cascade and PGI2, followed by muscarinic pathways and calcium channels.

The Aortic function of Male UC Davis Type 2 Diabetes Mellitus (UCD‐T2DM) Rats: Possible Involvement of Potassium Channels

UC Davis Type 2 Diabetes Mellitus (UCD‐T2DM) rat is a validated model of type 2 diabetes mellitus. UCD‐T2DM is characterized by polygenic, adult‐onset obesity and spontaneous β‐cell failure and, as a result, more closely models the pathophysiology of type 2 diabetes in humans than other rodent models. The objectives of this study were to determine whether the aortic function is altered in male UCD‐T2DM rats, and to test the hypothesis that potassium (K+) channels contribute in modulating vascular reactivity of aorta in this model. Endothelium‐dependent vasodilation (EDV) to acetylcholine (ACh, 10‐8 to 10‐5M) was measured in intact aortic rings pre‐contracted with phenylephrine (PE, 2μM) before and after pretreatment with tetraethylammonium (TEA, 2 mM), a non‐selective K+ channel blocker. Endothelium‐independent vasodilation to sodium nitroprusside (SNP, 10‐9 to 10‐5 M) was assessed in endothelium‐denuded rings pre‐contracted with PE (2μM). Furthermore, constrictor response curves to PE (10‐8 to 10‐5 M) were generated before and after incubation with L‐NAME (200μM), an endothelial nitric oxide synthase (eNOS) inhibitor.ACh responses were significantly potentiated in aortic rings of male UCD‐T2DM rats. Both maximal relaxation and sensitivity to ACh were significantly enhanced compared to those in controls. Incubation of aortic rings with TEA blunted the relaxation responses to ACh in both groups. However, the inhibitory effect of TEA on the ACh‐induced relaxation in UCD‐T2DM was greater than that in control rats. The smooth muscle sensitivity to NO as measured by SNP‐induced relaxation was not altered in aorta of UCD‐T2DM group. The responsiveness to PE was significantly enhanced in UCD‐T2DM rats. Accordingly, the basal nitric oxide (NO), as indicated by the potentiation of the response to PE after L‐NAME, was reduced in aorta of this group.These data, for the first time, show that the aortic function of male UCD‐T2DM rats is altered and that K+ channels may be involved. Further studies is required to document the underlying mechanisms of the altered vascular reactivity and to identify the contribution of specific subtypes of K+ channels in the potentiation of aortic endothelial function in this model.Support or Funding InformationSupported by NIHLBI, R15HL128988

Role of inducible nitric oxide synthase in endothelium-independent relaxation to raloxifene in rat aorta.

Raloxifene can induce both endothelium-dependent and -independent relaxation in different arteries. However, the underlying mechanisms by which raloxifene triggers endothelium-independent relaxation are still incompletely understood. The purpose of present study was to examine the roles of NOSs and Ca2+ channels in the relaxant response to raloxifene in the rat isolated, endothelium-denuded aorta. Changes in isometric tension, cGMP, nitrite, inducible NOS protein expression and distribution in response to raloxifene in endothelium-denuded aortic rings were studied by organ baths, radioimmunoassay, Griess reaction, western blot and immunohistochemistry respectively. Raloxifene reduced the contraction to CaCl2 in a Ca2+ -free, high K+ -containing solution in intact aortic rings. Raloxifene also acutely relaxed the aorta primarily through an endothelium-independent mechanism involving NO, mostly from inducible NOS (iNOS) in vascular smooth muscle layers. This effect of raloxifene involved the generation of cGMP and nitrite. Also, it was genomic in nature, as it was inhibited by a classical oestrogen receptor antagonist and inhibitors of RNA and protein synthesis. Raloxifene-induced stimulation of iNOS gene expression was partly mediated through activation of the NF-κB pathway. Raloxifene was more potent than 17β-estradiol or tamoxifen at relaxing endothelium-denuded aortic rings by stimulation of iNOS. Raloxifene-mediated vasorelaxation in rat aorta is independent of a functional endothelium and is mediated by oestrogen receptors and NF-κB. This effect is mainly mediated through an enhanced production of NO, cGMP and nitrite, via the induction of iNOS and inhibition of calcium influx through Ca2+ channels in rat aortic smooth muscle.

Teucrium polium-induced Vasorelaxation Mediated by Endothelium-dependent and Endothelium-independent Mechanisms in Isolated Rat Thoracic Aorta.

Objective:There are some reports on hypotensive and antispasmodic effects of Teucrium polium L. (Lamiaceae) (TP).Subjects and Methods:The activity of different concentrations of TP extract (1, 2, 4 and 8 mg/ml) was evaluated on contractile responses of isolated aorta to potassium chloride (KCl) and phenylephrine (PE).Results:The cumulative concentrations of the extract induced a concentration-dependent relaxation in the aorta precontracted by PE and KCl. Extract-induced vasorelaxations in denuded aortic rings precontracted by PE and KCl at lower concentrations were considerably less than intact aortic rings, but this effect was significantly more at concentrations of 4 mg/ml for PE-, 4 and 8 mg/ml for KCl-induced contractions. All the extract concentrations (except 1 mg/ml) significantly relaxed PE-induced contraction in the presence of NG-nitro-L-arginine methyl ester. Indomethacin reduced effectively extract-induced vasorelaxation at 1 and 2 mg/ml. The extract reduced PE- and KCl-induced contractions in the presence of cumulative calcium concentrations and after incubation with diltiazem; this vasorelaxant effect of TP was decreased. TP-induced relaxation was inhibited by heparin, ruthenium red, glibenclamide, and tetraethylammonium, but 4-aminopyridine had no effect on TP-induced relaxation.Conclusion:TP extract has vasorelaxant effect on isolated rat thoracic aorta which mediated by endothelium-dependent and endothelium-independent mechanisms. The relaxation mainly was mediated by inhibition of calcium influx in vascular smooth muscle cells. It seems that the vasorelaxant effect of extract at lower concentrations was mediated by nitric oxide and prostacyclin.SUMMARY The vasodilatory effect of Teucrium polium L. was mediated by several mechanisms. First: Teucrium polium L. inhibited receptor operated ROCC and VDCC. Second: Teucrium polium L. also inhibited KATP and KCa channels. Third: Teucrium polium L. blocked IP3 receptor and reduced the release of calcium from intracellular source. Forth: Teucrium polium L. increased the release on NO and PGI2 from endothelial cells. Abbreviations Used: ROCC: Receptor operated calcium channels, VDCC: Voltage dependent calcium channels, PLC: Phospholipase C, IP3: 1,4,5 triphosphate inositol, IP3R: IP3 receptors, SR: sarcoplasmic reticulum, RYR: ryanodine receptors, K+ATP: ATP-sensitive potassium channel, K+Ca: Calcium-activated potassium channel, cAMP: Cyclic adenosine monophosphate, cGMP: Cyclic guanosine monophosphate, PGI2: Prostaglandin I2, NO: Nitric oxide

The Effects of Glycerl Trinitrate and Adenosine 5-Triphosphate on Activation of Potassium Channel-Mediated Vasorelaxation in Female rats aortic Smooth Muscle.

Nitric oxide (NO) is produced from virtually all cell types composing the cardiovascular tissue and regulates vascular function through fine regulation of excitation–contraction coupling. Endogenous metabolites play a major role in coronary autoregulation. Therefore, the aim of the present study is to investigate the contribution of Glyceryl trinitrate (GTN) and Adenosine 5-triphosphate (ATP) mediated relaxation in rat aortic smooth muscle in intact and endothelium denuded endothelium rings precontracted with Phenylephrine (PE). The thoracic aorta was isolated, cut into rings, and mounted in organ-bath chambers and isometric tension was recorded using PowerLab Data Acquisition System (Model ML 870). The results showed that GTN as NO donor produced dose-dependent relaxation in intact aortic rings precontracted with PE (1 µM) that disinhibited in the presence of Glibenclamide (GLIB), while GLIB attenuate the response induced by ATP in intact aortic rings. L-nitroarginine methylester (L-NAME) an antagonist for nitric oxide synthases (NOS), not abolish the response induced by GTN (Emax 55.28% ± 0.18). Caffeine, ATP receptors antagonist, were partially inhibit the relaxation induced by ATP (vasodilation rate decreased by about 20.57 %). In endothelium denuded aortic rings, vasorelaxation induced by ATP were significantly attenuated , while GTN significantly increased relaxation by removing endothelium. These results suggested that (1) ATP-dependent potassium channel did not involve in GTN inducing vasorelaxation while KATP and A2Breceptors have a role in ATP mediated vasorelation (2) ATP partially dependent on endothelium in contrast to NO donors that independent to endothelium.