Phenylephrine-induced Contraction Research Articles

Shear Stress–dependent Effects of Lysophosphatidic Acid on Agonist-induced Vasomotor Responses in Rat Mesenteric Artery

We have previously shown that lysophosphatidic acid (LPA), a bioactive plasma lysophospholipid, markedly accelerates shear stress-induced Ca2+ responses in cultured vascular endothelial cells (ECs). This study aimed to demonstrate the impact of LPA and luminal shear stress on vasomotor regulation in the isolated rat mesenteric artery (MA) using a videomicroscopic technique. Although the addition of LPA to the perfusate in a concentration range of 0.03-0.3 μM had no significant effect on the basal MA tone, LPA in a similar concentration range led to increased phenylephrine-induced MA contraction and reduced acetylcholine-induced MA relaxation under physiological shear conditions. These vasomodulatory actions of LPA, which vanished upon removal of ECs, were positively dependent on luminal shear stress levels and were markedly inhibited by the LPA receptor antagonist Ki16425, the cyclooxygenase inhibitor indomethacin, and the thromboxane A2 receptor antagonist SQ29548. These data thus suggest that LPA can modify the agonist-induced vasomotor responses in MAs in a shear stress-dependent manner. This effect of LPA was mediated through ECs, the LPA receptor, and cyclooxygenase/thromboxane A2 signaling.

The semi-synthetic kaurane ent-16α-methoxykauran-19-oic acid induces vascular relaxation and hypotension in rats

The present work investigates the mechanisms involved in the vasorelaxant effect of ent-16α-methoxykauran-19-oic acid (KA–OCH3), a semi-synthetic derivative obtained from the kaurane-type diterpene ent-kaur-16-en-19-oic acid (kaurenoic acid). Vascular reactivity experiments were performed in aortic rings isolated from male Wistar rats using standard muscle bath procedures. The cytosolic calcium concentration ([Ca2+]c) was measured by confocal microscopy using the fluorescent probe Fluo-3 AM. Blood pressure measurements were performed in conscious rats. KA–OCH3 (10, 50 and 100μmol/l) inhibited phenylephrine-induced contraction in either endothelium-intact or endothelium-denuded rat aortic rings. KA–OCH3 also reduced CaCl2-induced contraction in a Ca2+-free solution containing KCl (30mmol/l) or phenylephrine (0.1μmol/l). KA–OCH3 (0.1–300μmol/l) concentration-dependently relaxed endothelium-intact and endothelium-denuded aortas pre-contracted with either phenylephrine or KCl, to a greater extent than kaurenoic acid. Moreover, a Ca2+ mobilisation study showed that KA–OCH3 (100μmol/l) inhibited the increase in Ca2+ concentration in smooth muscle and endothelial cells induced by phenylephrine or KCl. Pre-incubation of intact or denuded aortic rings with NG-nitro-l-arginine methyl ester (L-NAME, 100μmol/l), 7-nitroindazole (100μmol/l), wortmannin (0.5μmol/l) and 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 1μmol/l) produced a rightward displacement of the KA–OCH3 concentration–response curve. Intravenous administration of KA–OCH3 (1–10mg/kg) reduced mean arterial blood pressure in normotensive rats. Collectively, our results show that KA–OCH3 induces vascular relaxation and hypotension. The mechanisms underlying the cardiovascular actions of KA–OCH3 involve blockade of Ca2+ influx and activation of the NO-cGMP pathway.

Helper-Dependent Adenovirus Is Superior to First-Generation Adenovirus for Expressing Transgenes in Atherosclerosis-Prone Arteries

Vascular gene transfer is a powerful tool for investigating and treating vascular diseases; however, its utility is limited by brevity of transgene expression and vector-associated inflammation. Helper-dependent adenovirus (HDAd), an advanced-generation adenovirus that lacks all viral genes, is superior to first-generation adenovirus (FGAd) in normal rabbit arteries. We compared HDAd to FGAd in arteries of cholesterol-fed rabbits, a model of early atherogenesis in which transgene expression might be decreased, and inflammation increased. Carotid arteries of chow- and cholesterol-fed rabbits were infused with FGAd, HDAd, or medium. HDAd expressed a transgene at least as well in arteries of cholesterol-fed rabbits as in arteries of chow-fed rabbits and expressed more durably than FGAd. In arteries of cholesterol-fed rabbits, HDAd stimulated less intimal growth, lipid deposition, and inflammation than FGAd. Neither vector affected phenylephrine-induced contraction or nitroprusside-mediated relaxation; however, both vectors decreased maximal acetylcholine-stimulated vasorelaxation. The relative absence of intimal growth in HDAd arteries could interfere with the utility of this model for testing atheroprotective genes; however, both coinfusion of FGAd and extension of cholesterol feeding yielded larger intimal lesions, on which atheroprotective genes could be tested. HDAd is superior to FGAd for expression of transgenes in atherosclerosis-prone arteries.

Vascular responses to 8‐nitro‐cyclic GMP in non‐diabetic and diabetic mice

8-Nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP), formed nitric oxide (NO)-dependently, is a physiological second messenger, yet little is known about its role in the pathophysiology of vascular diseases. To study the pharmacological activity of 8-nitro-cGMP in diabetic mice, we compared its effects on vascular reactivity of aortas from non-diabetic and diabetic mice. Vascular tension recording was performed in thoracic aortic rings from wild-type (C57BL/6), non-diabetic db/+ and obese/diabetic db/db mice. Endothelial NO synthase (eNOS) uncoupling and superoxide were tested by Western blot and dihydroethidium fluorescence respectively. 8-Nitro-cGMP, at concentrations up to 10 µM, enhanced phenylephrine-induced contractions in aortas from C57BL/6 and db/+ mice, but not from db/db mice. This enhancement was not observed with 8-bromo-cGMP. Pretreatment of aortas from C57BL/6 and db/+ mice with l-NAME (100 µM), superoxide dismutase (100 U·mL(-1) ) or tiron (1 mM), abolished 8-nitro-cGMP-induced enhancement of the phenylephrine contraction. In 8-nitro-cGMP (10 µM)-treated C57BL/6 aortas, eNOS dimer/monomer ratio was significantly decreased and vascular superoxide production increased, suggesting that 8-nitro-cGMP-induced superoxide production via eNOS uncoupling may mediate the enhancement of the phenylephrine contraction. At higher concentrations (>10 µM), 8-nitro-cGMP produced relaxation of the phenylephrine-contracted aortas from C57BL/6, db/+ and db/db mice. The 8-nitro-cGMP-induced relaxation in db/db mouse aortas was found to be resistant to a phosphodiesterase 5 inhibitor, zaprinast (1 µM). The vasodilator effect of 8-nitro-cGMP may contribute to amelioration of the vascular endothelial dysfunction in diabetic mice, representing a novel pharmacological approach to prevent the complications associated with diabetes.

Age‐related Changes in Nitric Oxide‐mediated Vasodilation of Cerebral Arteries from Newborn Piglets

This study analyses the age-related changes on the vasodilation mediated by endothelial nitric oxide (NO) in rings of cerebral anterior and communicating arteries from 1–3- (Group 1) or 7–10- (Group 2) day-old piglets. Rings were contracted with phenylephrine (10−5 M) in the presence of indomethacin (10−4 M); then, concentration-response curves to bradykinin (10−10–10−6 M) and to exogenous NO (10−9–10−5 M) were performed. The incubation of segments with L-arginine (10−4 M) or NG-nitro-L-arginine methylester (L-NAME; 3 times 10−5 M) decreased and increased, respectively, the phenylephrine-induced contraction; L-NAME enhanced the basal tension also. Bradykinin relaxation was greater in Group 1 than in Group 2. In Group 1, the incubation with L-arginine did not increase bradykinin relaxation, but incubation with L-NAME abolished it. In Group 2, L-Arginine augmented and L-NAME reduced, but did not abolish, bradykinin relaxation. Vasodilatory response to exogenous NO was higher in Group 1 than in Group 2. We conclude that there is a basal and stimulated NO formation in endothelial cells of newborn piglet cerebral arteries, that the stimulated NO production and the sensitivity to NO are higher in vessels from 1–3-day-old piglets, and that L-arginine supplementation can increase the NO production in the vasculature of 7–10-day-old piglets to overcome its lowest sensitivity to NO.

Coupling of α1-Adrenoceptors to ERK1/2 in the Human Prostate

Introduction: α₁-Adrenoceptors are considered critical for the regulation of prostatic smooth muscle tone. However, previous studies suggested further α₁-adrenoceptor functions besides contraction. Here, we investigated whether α₁-adrenoceptors in the human prostate may activate extracellular signal-regulated kinases (ERK1/2). Methods: Prostate tissues from patients undergoing radical prostatectomy were stimulated in vitro. Activation of ERK1/2 was assessed by Western blot analysis. Expression of ERK1/2 was studied by immunohistochemistry. The effect of ERK1/2 inhibition by U0126 on phenylephrine-induced contraction was studied in organ-bath experiments. Results: Stimulation of human prostate tissue with noradrenaline (30 µM) or phenylephrine (10 µM) resulted in ERK activation. This was reflected by increased levels of phosphorylated ERK1/2. Expression of ERK1/2 in the prostate was observed in smooth muscle cells. Incubation of prostate tissue with U0126 (30 µM) resulted in ERK1/2 inhibition. Dose-dependent phenylephrine-induced contraction of prostate tissue was not modulated by U0126. Conclusions: α₁-Adrenoceptors in the human prostate are coupled to ERK1/2. This may partially explain previous observations suggesting a role of α₁-adrenoceptors in the regulation of prostate growth.

Alterations in perivascular adipose tissue structure and function in hypertension

We studied the structural and the functional alterations of perivascular adipose tissue (PVAT) in hypertension with spontaneously hypertensive rats (SHR). Measured with dual energy X-ray absorptiometry, a smaller body fat mass and a greater lean mass were found in SHR than in Wistar–Kyoto (WKY) rats, while body weight was comparable between them. In the thoracic PVAT, the density and the total number of brown adipocytes were greater in SHR than in WKY rats, while the cross section area of PVAT was similar between them. In functional assessment, four types of vessel preparations (with either intact PVAT or intact endothelium, or with both, or without both) were employed. Vessels with intact PVAT from SHR contracted more to phenylephrine than that from WKY rats, while vessels without PVAT exhibited comparable contractile response to phenylephrine between SHR and WKY rats. Both endothelium-dependent and -independent components of PVAT-associated attenuation of phenylephrine-induced contraction were reduced in SHR as compared with that of WKY rats. Bioassay experiments were carried out to assess the transferable relaxation factor from the PVAT. Transfer of bathing solution incubated with PVAT-intact vessel caused less relaxation in SHR recipients than in WKY rats, and the relaxation response was abolished by D-Ala7-angiotensin-(1–7), an angiotensin-(1–7) receptor antagonist. In summary, PVAT-associated inhibition of vessel contractile response to agonist was impaired in SHR, and the impairment involved both endothelium-dependent and -independent mechanisms. The functional impairment observed in SHR PVAT may be related to changes in adipocyte composition but not to reduced PVAT mass in SHR.

Indigo carmine enhances phenylephrine-induced contractions in an isolated rat aorta

BackgroundThe intravenous administration of indigo carmine has been reported to produce transiently increased blood pressure in patients. The goal of this in vitro study was to examine the effect of indigo carmine on phenylephrine-induced contractions in an isolated rat aorta and to determine the associated cellular mechanism with particular focus on the endothelium-derived vasodilators.MethodsThe concentration-response curves for phenylephrine were generated in the presence or absence of indigo carmine. Phenylephrine concentration-response curves were generated for the endothelium-intact rings pretreated independently with a nitric oxide synthase inhibitor, Nω-nitro-L-arginine methyl ester (L-NAME), a cyclooxygenase inhibitor, indomethacin, and a low-molecular-weight superoxide anion scavenger, tiron, in the presence or absence of indigo carmine. The fluorescence of oxidized dichlorofluorescein was measured in rat aortic vascular smooth muscle cells cultured in the control, indigo carmine alone and tiron plus indigo carmine.ResultsIndigo carmine (10-5 M) increased the phenylephrine-induced maximum contraction in the endothelium-intact rings with or without indomethacin, whereas indigo carmine produced a slight leftward shift in the phenylephrine concentration-response curves in the endothelium-denuded rings and L-NAME-pretreated endothelium-intact rings. In the endothelium-intact rings pretreated with tiron (10-2 M), indigo carmine did not alter phenylephrine concentration-response curves significantly. Indigo carmine (10-5 M) increased the fluorescence of oxidized dichlorofluorescein in the vascular smooth muscle cells, whereas tiron abolished the indigo carmine-induced increase in oxidized dichlorofluorescein fluorescence.ConclusionsIndigo carmine increases the phenylephrine-induced contraction mainly through an endothelium-dependent mechanism involving the inactivation of nitric oxide caused by the increased production of reactive oxygen species.

Inhibitory Effect of Fentanyl on Phenylephrine-Induced Contraction on Rabbit Aorta

This in vitro study was designed to assess the effects of fentanyl on isolated rabbit thoracic aorta rings contracted with phenylephrine. Methods included contraction of aorta rings with phenylephrine (10–5 M) and recording the changes after increasing concentrations of fentanyl (10–9 M – 10–5 M). Similar experiments were done after incubation with Nω- nitro-L-arginine methyl ester (10–4 M), indomethacin (10-5 M), naloxone (10–5 M), ouabain (10–5 M), TEA (10–4 M) and glibenclamide (10–5 M). It was revealed that, fentanyl causes relaxation in rabbit aorta rings precontracted with phenylephrine. Removal of endothelium significantly reduces the relaxant response to fentanyl. Nitric oxide synthase inhibitor L-NAME, K+ channel blocker glibenclamide and Na+/K+ ATPase inhibitor ouabain inhibits the relaxant effect of fentanyl in endothelium intact aorta rings. These results suggest that fentanyl causes dose dependent vasodilatation in the rabbit aorta via activation of KATP channels and Na+-K+ -ATPase, and nitric oxide released from endothelium.

Vasodilatory effects of cinnamaldehyde and its mechanism of action in the rat aorta

The vasodilatory effect of cinnamaldehyde was investigated for its mechanism of action using isolated rings of rat aorta. Cinnamaldehyde relaxed aortic rings precontracted with phenylephrine in a dose-dependent manner, was not affected by either the presence or removal of the endothelium. Pretreatment with NG-nitro-L-arginine methyl ester and 1H-[1,2,4]-oxadiazole-[4,3-a]-quinoxalin-1-one could not block vasodilation by cinnamaldehyde, indicating that nitric oxide signaling is not involved. Potassium channel blockers, such as glibenclamide, tetraethylammonium, and BaCl2, had no effect on the relaxation produced by cinnamaldehyde. In addition, treatment with either indomethacin or propranolol did not affect cinnamaldehyde-induced vasodilatation. On the other hand, pretreatment of endothelium-denuded rings with cinnamaldehyde significantly inhibited vasoconstriction induced by endogenous vasoconstrictors, including angiotensin II, 5-hydroxytryptamine, dopamine, endothelin-1, and phenylephrine. In a Ca2+-free experimental setting, this natural vasodilator not only blocked Ca2+ influx-dependent vasoconstriction by either phenylephrine or KCl, but also inhibited phenylephrine-induced tonic contraction, which relies on intracellular Ca2+ release. This study shows that endothelium-independent, Ca2+ influx and/or an inhibitory release mechanism contributes to the vasodilatory effect of cinnamaldehyde.

Indigo carmine enhances phenylephrine-induced contractions in an isolated rat aorta

Indigo carmine enhances phenylephrine-induced contractions in an isolated rat aorta

J052012 ソノポレーション法とチャネル遺伝子を用いた末梢循環障害の新規治療法の確立作成について([J05201]ドラッグデリバリーシステムでの流動現象とデバイス開発(1))

The combination of ultrasound and nano-bubbles coated with lipid bilayers (i.e. hybrid nano-bubbles) induces transient membrane permeability, leading to direct delivery of exogenous molecules (such as plasmid, siRNA, panticancer drugs, proteins etc.) into cells with minimal invasiveness. This method is generally termed `sonoporation' in drug delivery systems parlance. When Kir6.2 genes have transfected into native smooth muscle layers of mouse aorta by use of sonoporation, RT-PCR analysis revealed the expression of Kir6.2 transcripts in vascular smooth muscle. When Kir6.2 genes, tagging with Myc-genes, were transfected into native smooth muscle layers using sonoporation, immunohistochemical studies have revealed that Kir6.2 and Myc proteins were co-expressed in vascular smooth muscle cells. The phenylephrine-induced contraction of mouse aorta was significantly reduced after the treatment of Kir6.2 gene-sonoporation, hyperpolaring the membrane potentials. These results suggest that Kir6.2 genes were functionally expressed in mouse vascular smooth muscles, causing a vascular relaxation due to the activity of Kir6.2.

Renal and vascular effects of Crotalus durissus cumanensis venom and its crotoxin fraction

In this study, we evaluated the actions of Crotalus durissus cumanensis venom (CDCmV), and its crotoxin (Crtx) fraction, on renal and vascular functions in Wistar rats. In isolated perfused kidneys, CDCmV (10 µg/mL) significantly increased the perfusion pressure (PP) from 110.7 ± 2.4 to 125.3 ± 2.8 mmHg after 30 minutes. This effect was accompanied by an increased renal vascular resistance (RVR) from 5.4 ± 0.1 to 6.2 ± 0.2 mmHg/mL.g-1.min-1. We observed decreases in urinary flow (UF) from 0.13 ± 0.01 to 0.05 ± 001 mL.g-1.min-1 and glomerular filtration rate (GFR) from 0.66 ± 0.06 to 0.18 ± 0.02 mL.g-1.min-1. Crtx did not change PP or RVR, but diminished GFR (from 0.65 ± 0.05 to 0.26 ± 003 mL.g-1.min-1) and UF (from 0.11 ± 0.008 to 0.09 ± 0.008 mL.g-1.min-1). Both CDCmV and Crtx reduced the percentage of tubular transport of sodium, chloride and potassium. The cytotoxicity of these substances against MDCK cells was tested by the MTT method: only CDCmV caused a decrease in the cell viability with an IC50 of 5.4 µg/mL. In endothelium-intact isolated aortic rings, CDCmV (0.1 to 30 µg/mL) increased the sustained phenylephrine-induced contraction to a value of 130.0 ± 6.6% of its corresponding control, but showed a relaxant effect in endothelium-denuded preparations. Similar results were observed in aortic rings contracted with potassium (40 mM). Crtx was ineffective in aortic ring assays. Thus, it is reasonable to suggest that the renal effects induced by the CDCmV may be due to its influence on the endothelium's ability to release factors that can alter the contractile behavior of vascular smooth muscle. In conclusion, CDCmV is toxic to kidney cells. It changes parameters of the renal function including the glomerular filtration rate, renal vascular resistance and tubular transport. The actions induced by CDCmV also involve endothelium-dependent vasoactive properties. Their effects may be only partially attributed to Crtx.

Characterization of α 1-adrenoceptor Subtypes Mediating Contraction in Human Isolated Ureters

To characterize the contractile functions of the α(1)-adrenoceptor (AR) subtypes present in the human ureter. Specimens were taken from patients with renal cancer ("upper ureters;" n = 51) or bladder cancer ("lower ureters;" n = 23) who had not been treated by chemotherapy, radiation therapy, or immunotherapy before surgery. Patients systemically taking an α(1)-AR agonist or antagonist were excluded from this study. The effects of α(1)-AR antagonists against phenylephrine (α(1)-AR agonist)-induced contractions were evaluated in human isolated ureteral preparations. Pooled data from all ureters showed that phenylephrine (α(1)-AR agonist) induced a concentration-dependent tonic contraction (pD(2) value, 4.92 ± 011). The phenylephrine-induced maximum contraction was significantly greater in lower ureters than in upper ones. Prazosin (nonselective α(1)-AR antagonist), silodosin (selective α(1A)-AR antagonist), and BMY-7378 (selective α(1D)-AR antagonist) all shifted the concentration-contractile response curve for phenylephrine to the right, the rank order of potencies in all ureters (pK(B) values) being silodosin (9.72 ± 0.14) > prazosin (8.64 ± 0.08) > BMY-7378 (7.04 ± 0.14). The α(1A)-AR antagonist silodosin was thus much more potent than the other 2 antagonists. Our results suggest that among α(1)-ARs, the α(1A) subtype plays the major role in contraction in the human ureter.

Endotoxin Induces Differentiated Contractile Responses in Porcine Pulmonary Arteries and Veins

Background/Aims: Sepsis-induced lung injury is characterized by pulmonary hypertension, edema and deteriorated gas exchange. As in vivo studies have indicated that bacterial endotoxin predominantly induces a pulmonary venous constriction, we aimed to investigate effects of endotoxin on isolated porcine pulmonary vessels. Methods: Pulmonary arteries and veins were examined using in vitro isometric force recordings. Endothelin-receptor protein expression and distribution were analyzed by Western blot and immunohistochemistry. Freshly isolated preparations and vessels incubated (24 h) with/without endotoxin (10 µg·ml^–1) were compared. The contractile responses to phenylephrine, UK14.304, U46619, PGF₂_α, endothelin-1 (ET-1) and sarafotoxin were recorded, as well as the relaxation in response to acetylcholine, isoproterenol and nitroprusside. Results: In freshly isolated vessels, phenylephrine-induced contractions had a 5-times larger amplitude in arteries than in veins. The amplitude of the contractions in response to sarafotoxin was nearly 2 times larger in veins than in arteries, but there was no difference in responses to ET-1. Endotoxin markedly reduced phenylephrine-induced contractions in both arteries and veins, whereas the responses to ET-1 and sarafotoxin were augmented in veins only. No apparent changes in ET receptor expression or distribution were detected with Western blot or immunohistochemistry. Conclusion: Endotoxin differentially and selectively alters the contractile responses of porcine pulmonary vessels in vitro, towards a situation where the α-1 adrenergic responses of arteries are attenuated and the ET responses of veins are augmented. In situations with high adrenergic activity and high circulating ET levels, such as sepsis, these results may provide a mechanism contributing to pulmonary hypertension and edema formation.

EFFECTS of Zoledronic ACID On eNOS Exppression and Vascular Contractility IN Rat Aorta

AbstractAbstract 4318Zoledronic acid (ZOL) is a potent nitrogen-containing bisphosphonate used in the treatment of skeletal metabolic disorders and bone metastatic diseases. It has been shown that the nitrogenous bisphosphonates inhibits enzymes of mevalonate pathway. Similar with statin derivatives, ZOL affects the biological activity of geranyl-geranylated proteins in mevalonate pathway, as shown for the small GTPase RhoA. Although, beneficial effects of statin derivatives on vascular tissue have been reported, there is no study on effects and of ZOL on endothelial functions in vascular tissue and mechanisms of its action. It is important to elucidate the mechanism regulating NO production for endothelial cells to develop new therapeutic strategies for the treatment of impaired endothelial function associated with the vascular diseases. The aim of this study is to demonstrate the molecular mechanism of ZOL in the regulation of endothelial responses and eNOS expression in rat aorta. For his aim, potassium chloride and phenyleprine induced vasoconstriction was evaluated in endothelium intact and denuded isolated rat aorta preparations (n=6) after incubation with ZOL 100 μM and the results were compared with those without ZOL incubation. In addition, to evaluate endothelium dependent or independent effects of ZOL, vasodilator effects of acetylcholine and sodium nitroprussid were tested in the presence and absence of ZOL. To evaluate the influence of protein geranylation in effect of ZOL, contractile effect of phenylephrine vasocontractions was tested after incubation with ZOL in the presence of geranylgeranyl pyrophosphate and farnesyl pyrophosphate, important enzymes of mevolonate pathway. In addition, eNOS mRNA expressions were evaluated with RT-PCR in intact rat aorta or after incubation with ZOL. According to our results, incubation with ZOL decreased potassium chloride and phenylephrine-induced contractions significantly. This decrease was reversed NO-syntase inhibitor Nı,-nitro-L-arginine methyl esther (L-NAME) 0.1mM. Additionally, incubation with ZOL, increased endothelium-dependent acethycholine-induced relaxations and this effect of ZOL was inhibited by L-NAME. In rat aorta preparations incubated with ZOL, eNOS mRNA expression was increased significantly (1.52 fold) compared with control group. According to these results, we herein provide the first experimental evidence for the physiological role of ZOL in the regulation of eNOS expression and the contractility in the vascular tissues. This effect of ZOL is probably via its influence on RhoA. Since the restoration of NO bioactivity is a major target of present pharmacological and non-pharmacological treatments in cardiovascular medicine, further laboratory and clinical studies to explore the effect of ZOL on vascular endothelium may be helpful to demonstrate the possible benefits. Disclosures:No relevant conflicts of interest to declare.

Cardiovascular effects of 1-nitro-2-phenylethane, the main constituent of the essential oil of Aniba canelilla, in spontaneously hypertensive rats

This study investigated the cardiovascular responses to the essential oil of Aniba canelilla (EOAC) and its main constituent 1-nitro-2-phenylethane (NP) in spontaneously hypertensive rats (SHRs). In anesthetized SHRs, intravenous (i.v.) bolus injections of EOAC (1-20 mg/kg) or NP (1-10 mg/kg) elicited dose-dependent hypotensive and bradycardiac effects, which were characterized in two periods (phases 1 and 2). The first rapid component (phase 1) evoked by EOAC and NP both at 10 mg/kg was absent after left ventricle injection, fully abolished by bilateral vagotomy and perineural treatment of both cervical vagus nerves with capsaicin (250 μg/mL) while remained unaltered by i.v. pretreatment with capsazepine (1 mg/kg) or ondansetron (30 μg/kg). In conscious SHRs, NP (5 and 10 mg/kg, i.v.) evoked rapid hypotensive and bradycardiac effects (phase 1) that were fully abolished by methylatropine (1 mg/kg, i.v.) pretreatment. In rat endothelium-containing mesenteric preparations, increasing concentrations (0.1-1000 μg/mL) of EOAC and NP relaxed the phenylephrine-induced contraction in a concentration-dependent manner. It is concluded that NP induces a vago-vagal bradycardiac and depressor reflex (phase 1) that apparently results from the stimulation of vagal pulmonary rather than cardiac C-fiber afferents. This effect does not appear to involve activation of either vanilloid TPRV(1) or 5-HT(3) receptors located on vagal sensory nerves. The phase 2 hypotensive response to i.v. NP seems to result, at least in part, from its direct vasodilatory effect on the peripheral smooth muscle. All in vivo and in vitro effects of EOAC are mostly attributed to the actions of its main constituent NP.

Macrophyllionium and Macrophyllines A and B, Oxindole Alkaloids from Uncaria macrophylla

An unusual oxindole alkaloid inner salt, macrophyllionium (1), and a pair of new tetracyclic oxindole alkaloids, macrophyllines A (2) and B (3), together with six known alkaloids, were isolated from the aerial parts of Uncaria macrophylla. Corynantheidine (8) exhibited moderate cytotoxicity against HL-60 and SW480 cells with IC(50) values of 13.96 and 23.28 μM, respectively. Dihydrocorynantheine (9) exhibited significant vasodilating activity against phenylephrine-induced contraction in rat thoracic aorta rings (IC(50) = 6.73 μg/mL). In addition, compounds 2, 6, and 9 showed weak inhibitory action on KCl-induced contraction.

Differential effects of statins on endogenous H 2S formation in perivascular adipose tissue

Hydrogen sulfide (H 2S) is a new gasotransmitter synthesized enzymatically from l-cysteine in cytosol and is oxidized in mitochondria. In the cardiovascular system, H 2S regulates vascular tone, inhibits atherogenesis, and protects against myocardial ischemia–reperfusion injury. We examined the effect of statins on vascular H 2S production. Male Wistar rats received pravastatin (40 mg/kg/day) or atorvastatin (20 mg/kg/day) for 3 weeks and then H 2S formation was measured in aortic media, periaortic adipose tissue (PAAT) and the liver. Only atorvastatin increased H 2S production in PAAT whereas both statins stimulated its formation in the liver. Neither statin affected H 2S production in aortic media. H 2S formation in post-mitochondrial supernatant was higher than in mitochondria-containing supernatant and was not influenced by statins in any tissue. In addition, oxidation of exogenous H 2S in isolated liver mitochondria was slower in statin-treated than in control rats. These data indicate that statins increase net H 2S production by inhibiting its mitochondrial oxidation. Statins had no effect on the activity of H 2S-metabolizing enzyme, sulfide:quinone oxidoreductase, measured at saturating coenzyme Q concentration. Both statins reduced CoQ 9 concentration in plasma and liver, but only atorvastatin decreased CoQ 9 in PAAT. Atorvastatin attenuated phenylephrine-induced contraction of PAAT+ but not of PAAT− aortic rings. Effects of atorvastatin on net H 2S production, mitochondrial H 2S oxidation and aortic contractility were abolished by supplementation of exogenous CoQ 9. In conclusion, lipophilic atorvastatin, but not hydrophilic pravastatin, increases net H 2S production in perivascular adipose tissue by inhibiting its mitochondrial oxidation. This effect is mediated by statin-induced CoQ 9 deficiency and results in the augmentation of anticontractile effect of perivascular adipose tissue.

Role of K ATP and L-type Ca 2+ channel activities in regulation of ovine uterine vascular contractility: effect of pregnancy and chronic hypoxia

Our objective was to determine whether the pregnancy and high altitude long-term hypoxia-mediated changes in uterine artery contractility were regulated by K(ATP) and L-type Ca(2+) channel activities. Uterine arteries were isolated from nonpregnant and near-term pregnant ewes that had been maintained at sea level (∼300 m) or exposed to high altitude (3801 m) for 110 days. Isometric tension was measured in a tissue bath. Pregnancy increased diazoxide, but not verapamil-induced relaxations. Long-term hypoxia attenuated diazoxide-induced relaxations in near-term pregnant uterine arteries, but enhanced verapamil-induced relaxations in nonpregnant uterine arteries. Diazoxide decreased the maximal response (E(max)) of phenylephrine-induced contractions in near-term pregnant uterin arteries but not nonpregnant uterine arteries in normoxic sheep. In contrast, diazoxide had no effect on phenylephrine-induced E(max) in near-term pregnant uterine arteries but decreased it in nonpregnant uterine arteries in long-term hypoxia animals. Verapamil decreased the E(max) and pD(2) (-logEC(50)) of phenylephrine-induced contractions in both nonpregnant uterine arteries and near-term pregnant uterine arteries in normoxic and long-term hypoxia animals, except nonpregnant uterine arteries of normoxic animals in which verapamil showed no effect on the pD(2). The results suggest that pregnancy selectively increases K(ATP), but not L-type Ca(2+) channel activity. Long-term hypoxia decreases the K(ATP) channel activity, which may contribute to the enhanced uterine vascular myogenic tone observed in pregnant sheep at high altitude hypoxia.