Rabbit Aortic Rings Research Articles

Antispasmodic, bronchodilator and blood pressure lowering properties of Hypericum oblongifolium – possible mechanism of action

The crude extract of Hypericum oblongifolium (Ho.Cr), which tested positive for flavonoids, saponins and tannins caused concentration-dependent (0.1-1.0 mg/mL) relaxation of spontaneous and high K(+) (80 mM)-induced contractions in isolated rabbit jejunum preparations, suggesting a Ca(++) antagonistic effect, which was confirmed when pretreatment of the tissue with Ho.Cr produced a rightward shift in the Ca(++) concentration-response curves, like that caused by verapamil. Ho.Cr relaxed carbachol (1 microM) and high K(+)-induced contractions in guinea pig tracheal preparations. It caused a dose-dependent (3-100 mg/kg) fall in arterial blood pressure of rats under anesthesia. In isolated guinea pig atria, Ho.Cr caused inhibition of both atrial force and rate of spontaneous contractions. When tested in rabbit aortic rings, Ho.Cr exhibited a vasodilator effect against phenylephrine (1 microM) and high K(+)-induced contractions. These results indicate that Ho.Cr possesses gastrointestinal, respiratory and cardiovascular inhibitory effects, mediated via a Ca(++) antagonist mechanism.

An operational model of pharmacological agonism: the effect of E/[A] curve shape on agonist dissociation constant estimation

An operational model of pharmacological agonism: the effect of E/[A] curve shape on agonist dissociation constant estimation

Paradoxical cholinergic and purinergic vascular reactivity of rabbit thoracic aorta cold-stored in University of Wisconsin solution.

Endothelial dysfunction has been reported in donor blood vessels destined for organ transplantation following cold-storage preservation with University of Wisconsin solution (UW). This was investigated in the present work. Segments of rabbit thoracic aorta were mounted on isometric fine-wire myographs at 37 degrees C and gassed with 95% O2/5% CO2. Concentration-dependent vasodilatations to acetylcholine and adenosine-5'-triphosphate (ATP) were obtained in freshly-harvested rabbit aortic rings, with and without the endothelium, and after 8 days of cold-storage, at 4 degrees C, in either UW, Krebs-Bülbring buffer (KBB) or saline. The action of the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) (100 microM) was evaluated upon the concentration-response curves to determine whether nitric oxide (NO) exerted any modulatory actions. Endothelium-dependent, NO-mediated responses to acetylcholine were unaltered after eight days of storage in UW, reduced after storage in KBB and absent after removal of the vascular endothelium, saline storage or after testing in the presence of L-NAME, suggesting improved NO-mediated endothelial function with the use of UW. Structural preservation was also confirmed using scanning electron microscopy. In contrast, endothelium-dependent responses to ATP were unchanged after eight days of storage in KBB but were reduced after storage in UW and saline, suggesting purinergic (ATP) endothelial dysfunction after storage in UW. L-NAME markedly reduced vasodilatation to ATP in freshly harvested rings and after eight days of storage in KBB. This reduction was statistically significant (P < 0.05, Student's two tailed, unpaired t-test) at -log (M) ATP concentrations of 5.5, 5.0, 4.5, 4.0 and 3.5. NO-dependent vasodilatation to ATP was not attenuated by L-NAME in UW-stored rings. Eight days' UW-storage of rabbit thoracic aortic rings appeared to have differential and paradoxical effects upon NO-dependent vasodilatation to acetylcholine and ATP. Morphological observations using electron microscopy suggested that UW preserved the vascular endothelium and this was verified by retained vascular reactivity of endothelium-dependent vasodilatations to acetylcholine. UW-storage however, significantly reduced endothelium-dependent relaxation to ATP thereby suggesting that P2Y-purinoceptors, which are located on the vascular endothelium, may be more susceptible to biodegradation than cholinergic receptors and may be responsible for endothelial dysfunction following transplantation.

Pharmacology and placental transfer of a human αv integrin monoclonal antibody in rabbits

Intetumumab is a human IgG1 anti-alphav-integrin monoclonal antibody that inhibits angiogenesis. Integrin binding and angiogenesis are important in reproduction including fertilization, implantation, and embryofetal development. These studies were designed to determine the pharmacological relevance of the rabbit for the evaluation of potential effects on embryofetal development and to evaluate the placental transfer of intetumumab in rabbits. In vitro pharmacology studies evaluated the binding of intetumumab to rabbit cells and the inhibition of vessel sprouting from rabbit aorta. For the evaluation of placental transfer, pregnant rabbits (8/group) were injected intravenously with intetumumab 50 or 100 mg/kg every 2 days from Gestation Day (GD)7 to GD19. Maternal sera, fetal homogenates/sera, and amniotic fluid were collected at necropsy on GD19 or GD28 for evaluation of intetumumab concentrations. Clinical condition of the dams was monitored and fetuses were screened for abnormalities. Intetumumab (5-40 microg/mL) inhibited aortic cell adhesion to vitronectin and vessel sprouting from rabbit aortic rings. Immunohistochemical staining of rabbit tissues demonstrated binding of intetumumab to placenta. Administration of intetumumab to pregnant rabbits was well tolerated by the dams and the fetuses did not show major abnormalities. Fetal exposure to intetumumab relative to maternal exposure was <0.1% on GD19 and 100-130% on GD29. The rabbit is a pharmacologically relevant species for evaluation of potential developmental effects of intetumumab. Intetumumab crosses the rabbit placenta during the fetal period (GD 19-28).

Effect of ketorolac and diclofenac on the impairment of endothelium-dependent relaxation induced by reactive oxygen species in rabbit abdominal aorta

BackgroundReactive oxygen species (ROS) induce lipid peroxidation and tissue damage in endothelium. We studied the influences of ketorolac and diclofenac on ROS effects using the endothelium of rabbit abdominal aorta.MethodsIsolated rabbit aortic rings were suspended in an organ bath filled with Krebs-Henseleit (K-H) solution bubbled with 5% CO2 and 95% O2 at 37.5℃. After being stimulated to contract with phenylephrine (PE, 10-6 M), changes in arterial tension were recorded following the cumulative administration of acetylcholine (ACh, 3 × 10-8 to 10-6 M). The percentages of ACh-induced relaxation of aortic rings before and after exposure to ROS, generated by electrolysis of K-H solution, were used as the control and experimental values, respectively. The aortic rings were pretreated with ketorolac or diclofenac at the same concentrations (10-5 M to 3 × 10-4 M), and the effects of these agents were compared with the effects of ROS scavengers: catalase, mannitol, sodium salicylate and deferoxamine and the catalase inhibitor, 3-amino-1,2,4-triazole (3AT).ResultsBoth ketorolac and diclofenac maintained endothlium-dependent relaxation induced by ACh in a dose-related manner inspite of ROS attack (P < 0.05 vs. control value). The 3AT pretreated ketorolac (3 × 10-3 M) group was decreased more significantly than un-pretreated ketorolac (P < 0.05).ConclusionsThese findings suggest that ketorlac and diclofenac preserve the endothelium-dependent vasorelaxation against the attack of ROS, in a concentration-related manner. One of the endothelial protection mechanisms of ketorolac may be hydrogen peroxide scavenging.

Pharmacological basis for the medicinal use of Zanthoxylum armatum in gut, airways and cardiovascular disorders

This study describes the gut, airways and cardiovascular modulatory activities of Zanthoxylum armatum DC. (Rutaceae) to rationalize some of its medicinal uses. The crude extract of Zanthoxylum armatum (Za.Cr) caused concentration-dependent relaxation of spontaneous and high K(+) (80 mM)-induced contractions in isolated rabbit jejunum, being more effective against K(+) and suggestive of Ca(++) antagonist effect, which was confirmed when pretreatment of the tissues with Za.Cr shifted Ca(++) concentration-response curves to the right, like that caused by verapamil. Za.Cr inhibited the castor-oil-induced diarrhea in mice at 300-1000 mg/kg. In rabbit tracheal preparations, Za.Cr relaxed the carbachol (1 microM) and high K(+)-induced contractions, in a pattern similar to that of verapamil. In isolated rabbit aortic rings, Za.Cr exhibited vasodilator effect against phenylephrine (1 microM) and K(+)-induced contractions. When tested in guinea pig atria, Za.Cr caused inhibition of both atrial force and rate of spontaneous contractions, like that caused by verapamil. These results indicate that Zanthoxylum armatum exhibits spasmolytic effects, mediated possibly through Ca(++) antagonist mechanism, which provides pharmacological base for its medicinal use in the gastrointestinal, respiratory and cardiovascular disorders.

Nitrite, NO and hypoxic vasodilation

The ability to deliver oxygen and other nutrients to working tissues at a rate acutely matched to demand is the quintessential function of the cardiovascular system. Thus, an understanding of the biochemical mechanisms involved in hypoxic vasodilation remains a major goal in vascular biology. Nitric oxide, its metabolites, and oxidation status are recognized as playing important roles in this process. Previous work examining how nitrite can be converted to bioactive nitric oxide (NO) under hypoxic conditions has focused on the role of the red blood cell and haemoglobin. In a recent issue of the British Journal of Pharmacology, Pinder et al. demonstrate that plasma nitrite, in the absence of haemoglobin, is capable of increasing the maximal dilation of rabbit aortic rings under hypoxic conditions. Furthermore, they demonstrate that this relaxation can occur with or without the endothelium. This observation, even if it is only a small proportion of the relaxant activity of nitrite, highlights how NO metabolites may be involved in a variety of mechanisms of vessel control.

Nitric oxide-donating carbonic anhydrase inhibitors for the treatment of open-angle glaucoma

Novel bi-functional compounds with a nitric oxide (NO)-releasing moiety bound to a dorzolamide scaffold were investigated. Several compounds were synthesized and their activity as selective carbonic anhydrase inhibitors (CAI) evaluated in vitro on recombinant hCA type I, II and IV enzyme isoforms where they showed different degrees of potency and selectivity to hCA II. A high resolution X-ray crystal structure for the CA II adduct with 8 confirmed the high affinity of this class of compounds for the enzyme. Compounds 4, 6, and 8 showed highly potent and efficacious NO-mediated properties as assessed by their vascular relaxant effect on methoxamine-precontracted rabbit aortic rings. Finally, compounds 4 and 6 exerted potent intraocular pressure (IOP) lowering effects in vivo in normotensive rabbits thereby anticipating their potential for the treatment of hypertensive glaucoma.

Change in high-sensitive C-reactive protein during abdominal aortic aneurysm formation

We try to clear the relationship between high-sensitive C-reactive protein (hsCRP) release and abdominal aortic aneurysm formation. A rabbit abdominal aortic aneurysm model was created by elastase perfusion. At days 10, 20, and 30 after elastase perfusion, mean serum hsCRP levels detected by ELISA increased over 200% over their basal level (n = 11, P < 0.05). Serum hsCRP levels were significantly higher in the aneurysm groups than in the sham controls by day 5 (n = 11, P < 0.05) and were positively correlated with percentage vessel diameter changes in the aneurysm group by day 10 (r = 0.8012, n = 33, P < 0.05). In the aneurysm group, increased serum CRP was derived from the liver in early stages, yet from dilated vessels in the later stages, as shown by immunostaining, western blot, and reverse transcriptase-PCR. Similar increased hsCRP levels were also observed in dissected rabbit aortic ring explants from the aneurysm model. Pretreatment with the stretch-activated channel blockers gadolinium or streptomycin, as well as nuclear factor-kappaB inhibitor SN50, blocked hsCRP production in the dilated aortic rings. Stretch-activated channel blockers also inhibited the activation of nuclear factor-kappaB. During abdominal aortic aneurysm formation, increased serum hsCRP levels derive from aneurysmal arteries with degenerating elastic lamina. This process is mediated by mechanical stretch-activated channel-dependent nuclear factor-kappaB translocation to the nucleus.

APD791, 3-Methoxy-N-(3-(1-methyl-1H-pyrazol-5-yl)-4-(2-morpholinoethoxy)phenyl)benzamide, a Novel 5-Hydroxytryptamine 2A Receptor Antagonist: Pharmacological Profile, Pharmacokinetics, Platelet Activity and Vascular Biology

We have evaluated the receptor pharmacology, antiplatelet activity, and vascular pharmacology of APD791 [3-methoxy-N-(3-(1-methyl-1H-pyrazol-5-yl)-4-(2-morpholinoethoxy)phenyl)benzamide] a novel 5-hydroxytryptamine 2A (5-HT(2A)) receptor antagonist. APD791 displayed high-affinity binding to membranes (K(i) = 4.9 nM) and functional inverse agonism of inositol phosphate accumulation (IC(50) = 5.2 nM) in human embryonic kidney cells stably expressing the human 5-HT(2A) receptor. In competition binding assays, APD791 was greater than 2000-fold selective for the 5-HT(2A) receptor versus 5-HT(2C) and 5-HT(2B) receptors, and was inactive when tested against a wide panel of other G-protein-coupled receptors. APD791 inhibited 5-HT-mediated amplification of ADP-stimulated human and dog platelet aggregation (IC(50) = 8.7 and 23.1 nM, respectively). Similar potency was observed for inhibition of 5-HT-stimulated DNA synthesis in rabbit aortic smooth muscle cells (IC(50) = 13 nM) and 5-HT-mediated vasoconstriction in rabbit aortic rings. Oral administration of APD791 to dogs resulted in acute (1-h) and subchronic (10-day) inhibition of 5-HT-mediated amplification of collagen-stimulated platelet aggregation in whole blood. Two active metabolites, APD791-M1 and APD791-M2, were generated upon incubation of APD791 with human liver microsomes and were also indentified in dogs after oral administration of APD791. The affinity and selectivity profiles of both metabolites were similar to APD791. These results demonstrate that APD791 is an orally available, high-affinity 5-HT(2A) receptor antagonist with potent activity on platelets and vascular smooth muscle.

Blood Pressure-lowering and Vascular Modulator Effects of Acorus calamus Extract Are Mediated Through Multiple Pathways

This investigation was aimed to provide a pharmacologic basis to the medicinal use of Acorus calamus in cardiovascular disorders. In normotensive anesthetized rats, crude extract of Acorus calamus and its ethylacetate and nHexane fractions caused a fall in mean arterial pressure. In rabbit aorta rings, crude extract was more potent against high K (80 mM), ethylacetate against phenylephrine (1 microM), whereas nHexane fraction was equipotent against both precontractions. Crude extract exhibited a vasoconstrictor effect on baseline. Pretreatment of aortic rings with crude extract and its fractions shifted Ca concentration-response curves to the right, similar to verapamil. Crude extract and ethylacetate fraction suppressed phenylephrine peak formation in Ca-free medium. In rat aorta preparations, crude extract exhibited endothelium-independent relaxation with a vasodilatory effect against high K. nHexane fraction caused an endothelium-dependent Nomega-nitro-l-arginine methyl ester-sensitive vasorelaxant along with ryanodine-sensitive vasoconstrictor effect on baseline tension and partially inhibited high K, although ethylacetate fraction caused an endothelium-independent relaxant and endothelium-dependent vasoconstrictor effect. These data indicate that crude extract possesses a combination of effects, relaxant effects mediated possibly through Ca antagonism in addition to a nitric oxide pathway, although the associated vasoconstrictor effects may be meant by nature to offset excessive vasodilatation, thus providing a pharmacologic rationale to its cardiovascular medi-cinal uses.

Anti-Ischemic Activity and Endothelium-Dependent Vasorelaxant Effect of Hydrolysable Tannins from the Leaves ofRhus coriaria(Sumac) in Isolated Rabbit Heart and Thoracic Aorta

The aim of this work was to investigate the cardioprotective activity of hydrolysable gallotannins from Rhus coriaria L. leaves extract (RCLE) in isolated rabbit heart preparations, submitted to low-flow ischemia/reperfusion damage. RCLE induces a dose-dependent normalization of coronary perfusion pressure (CPP), reducing left ventricular contracture during ischemia, and improving left ventricular developed pressure and the maximum rate of rise and fall of left ventricular pressure at reperfusion. Creatinine kinase (CK) and lactate dehydrogenase (LDH) outflow were significantly reduced during reperfusion. In parallel there was a rise in the release of the cytoprotective 6-ketoprostaglandin F (1alpha) (6-keto-PGF (1alpha)) and a decrease of tumor necrosis factor-alpha (TNF-alpha), both significant only at the highest RCLE concentrations (150-500 microg/mL). The vasorelaxant activity of RCLE was studied in isolated rabbit aorta rings precontracted with norepinephrine (NE) with and without endothelium. The vasorelaxation induced by RCLE was predominantly endothelium-dependent as demonstrated by the loss of RCLE vasorelaxant ability in i) de-endothelized rings and ii) in intact aortic rings after pretreatment with NG-monomethyl- L-arginine (L-NMMA) and 1 H-[1.2.4]oxadiazolo[4.3- A]quinoxalin-1-one (ODQ). The inhibition of vasorelaxation in intact rings by indomethacin (INDO) demonstrates the ability of RCLE to modulate the coronary endothelium cyclooxygenase (COX) pathway. The K-ATP channel antagonist glibenclamide (GLIB) was ineffective. The antioxidant activity of RCLE, investigated in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) model and in living cell systems (rat erythrocytes), was stronger than that of gallic acid, ascorbic acid and trolox. The structure of its main bioactive constituents, profiled by HPLC-ESI-HR-S, comprised a mixture of polygalloylated D-glucopyranose with different degrees of galloylation and 3- O-methylgallic acid. The cardiovascular protective effect of RCLE seems to be due to an interplay of different factors: COX pathway activation, TNF-alpha inhibition, endothelial nitric oxide synthase (eNOS) activation, and free radical and ROS scavenging.

Gingival fibroblast inhibits MMP-7: Evaluation in an ex vivo aorta model

Matrix metalloproteinases (MMP) play a deleterious role in numerous vascular diseases. In contrast, gingival matrix remodelling is adequately regulated by the gingival fibroblast (GF). Here, we aimed to evaluate the GF activity on MMP-7 expression and secretion in coculture with aorta rings. We evaluated MMP-7 transcription and secretion in rabbit aorta rings cultured or not with gingival fibroblasts in collagen gels. GF induced an increase of TIMP-1 transcription and secretion, followed, similarly to other MMPs, by the formation of TIMP-1/MMP-7 complexes. There was also a decrease of MMP-7 mRNA by RT-PCR in aorta rings cocultured with gingival fibroblasts. Interestingly, in contrast with other MMPs (which were not influenced at a transcription level), GF stimulated the release of TGF-β1, which in turn inhibited the transcription and synthesis of MMP-7, as shown by neutralizing MMP-7 inhibition due to gingival fibroblast by overexpressing decorin (a TGFβ1 inhibitor) or by silencing TGFβ1 using siRNA. We showed that healing properties of the GF could be transposed to another organ, i.e., ex vivo aneurism model, implicating a down-regulation of MMP-7.

Receptor tyrosine kinases as mediators of injury-induced bradykinin B 1 receptor expression in rabbit aortic smooth muscle

Prolonged in vitro incubation of rabbit aortic rings allows recording contractile responses mediated by the inducible bradykinin B 1 receptors; addition of interleukin (IL)-1 or epidermal growth factor (EGF) to the bathing fluid increases the rate of sensitization, a process partially inhibited by the nonspecific Tyr-kinase inhibitor genistein. The recent development of specific inhibitors for receptor associated Tyr-kinase activities (tyrphostin AG 1478 for EGF receptor, sunitinib for VEGF receptor and others) allows assessing the role of such signaling molecules in this process. AG 1478 reduced the potentiating effects of exogenous EGF, and also the spontaneous sensitization to the agonist des-Arg 9-bradykinin. Sunitinib or GM 6001, a wide spectrum inhibitor of metalloproteinases, had no effect on these responses. In rabbit aortic smooth muscle cells, the cytokines IL-1β and EGF increased the density of binding sites for [ 3H]Lys-des-Arg 9-bradykinin in 4 h; AG 1478 reduced only the effect of exogenous EGF. IL-1 receptor antagonist decreased both the effect of IL-1β and of EGF in rabbit smooth muscle cells. EGF was weakly and slowly coupled to nuclear factor-κB nuclear translocation in these cells, as compared to the effect of IL-1β. EGF-induced EGF receptor autophosphorylation and ERK1/2 phosphorylation was selectively inhibited by AG 1478 in smooth muscle cells; Lys-des-Arg 9-bradykinin did not transactivate EGF receptor in these cells. While the Tyr-kinase activity sensitive to AG 1478 is recruited by tissue damage and exogenous EGF to upregulate bradykinin B 1 receptors in freshly isolated aortas, this signaling system interacts with others (e.g., IL-1) for the optimal expression of B 1 receptors.

C-Nitroso Donors of Nitric Oxide

A complete understanding of the biological activity of nitric oxide (NO) is complicated by the different reactivity profiles of its various species and by the often complex decomposition behavior of the NO progenitors in common use. Here, we report that appropriately substituted C-nitroso compounds act solely as donors of neutral nitric oxide through a first-order homolytic C-N bond scission to release up to 88% nitric oxide in DMSO at 25 degrees C. The reaction produces a carbon radical, and the yield of nitric oxide is dependent on the availability of radical traps. C-Nitroso compounds are sources of biologically active neutral NO and display potent NO bioactivity in a rabbit aortic ring assay.

Blood Pressure Lowering and Vasomodulator Effects of Piperine

This study was aimed to explore underlying mechanism(s) of cardiovascular effects of piperine. Intravenous administration of piperine caused a dose-dependent (1 to 10 mg/kg) decrease in mean arterial pressure (MAP) in normotensive anesthetized rats; the next higher dose (30 mg/kg) did not cause any further change in MAP. The fall in blood pressure (BP) was followed by small increase in MAP after each dose. In Langendorrf's rabbit heart preparation, piperine caused partial inhibition and verapamil caused complete inhibition of force and rate of ventricular contractions and coronary flow. In rabbit aortic rings, piperine inhibited high K+ (80 mM) precontractions and partially inhibited phenylephrine (PE), suggesting Ca2+ channel blockade (CCB), which was further confirmed when pretreatment of tissues with piperine caused rightward shift in Ca2+ concentration-response curves, similar to verapamil. In Ca2+-free medium, piperine (1 to 30 microM) exhibited vasoconstrictor effect. In rat aorta, piperine demonstrated endothelium-independent vasodilator effect and was more potent against high K+ precontractions than PE. In bovine coronary artery preparations, piperine inhibited high K+ precontractions completely. These data indicate that piperine possesses a blood pressure-lowering effect mediated possibly through CCB, while consistent decrease in BP was restricted by associated vasoconstrictor effect. Additionally, species selectivity exists in the CCB effect of piperine.

Effect of oral organic nitrates on expression and activity of vascular soluble guanylyl cyclase

The regulation of vascular soluble guanylyl cyclase (sGC) expression by nitric oxide (NO) is still under discussion. In vitro, NO has been shown to downregulate the expression of sGC but it is unclear if this mechanism is operative in vivo and occurs during nitrate treatment. We investigated whether high dose isosorbide mononitrate (ISMN) or pentaerythrityl tetranitrate (PETN) treatment changes vascular sGC expression and activity in vivo. New Zealand White rabbits received a standard diet, 2 or 200 mg ISMN kg(-1) d(-1) for 16 weeks, and C57BL/6 mice received a standard diet, 6, 60 or 300 mg PETN kg(-1) d(-1) for four weeks. Absorption was checked by measuring the plasma levels of the drug/metabolite. Western blots of rabbit aortic rings showed similar protein levels of sGC alpha1- (P=0.2790) and beta1-subunits (P=0.6900) in all groups. Likewise, ANOVA showed that there was no difference in the expression of sGC in lungs of PETN-treated mice (P=0.0961 for alpha1 and P=0.3709 for beta1). The activities of isolated sGC in response to SNAP (1 microM-1 mM) were identical in aortae of ISMN-treated rabbits (P=0.0775) and lungs of PETN-treated mice (P=0.6348). The aortic relaxation response to SNAP slightly decreased at high ISMN but not at high PETN. These data refute the hypothesis that therapeutic treatment with long acting NO donors has a significant impact on the regulation of vascular sGC expression and activity in vivo.

Strawberry Extract Caused Endothelium-Dependent Relaxation through the Activation of PI3 Kinase/Akt

Polyphenolic compounds are vasodilators and help to lower the risk of cardiovascular diseases. We hypothesized that a freeze-dried strawberry powder that is rich in polyphenolic compounds would cause an endothelium-dependent relaxation (EDR) through the activation of phosphatidylinositol-3 (PI3)-kinase/protein kinase B (Akt) in rabbit aorta. The powder was prepared by freeze drying a homogenate of ripe California strawberry fruits. An aqueous extract of strawberry powder was applied to rabbit aortic rings suspended in organ baths containing Krebs-Henseleit buffer maintained at 37 degrees C. In aortic rings precontacted with norepinephrine, the extract produced a dose-dependent relaxation. The maximum relaxations elicited by the extract (73.1 +/- 1.0%) were similar to those elicited by acetylcholine (68.2 +/- 1.5%) ( n = 14 for each). The relaxation by strawberry extract was abolished by removal of the endothelium and by prior incubation with N omega-nitro- l-arginine methyl ester hydrochloride (L-NAME), confirming the essential role of endothelial nitric oxide synthase (eNOS). The responses to the strawberry were also abolished by incubation with wortmannin and LY294002, which are inhibitors of PI3 kinase. Using immunoblotting, we also demonstrated that the strawberry extract induced the phosphorylation of both Akt and eNOS in human umbilical vein endothelial cells (HUVECs) via PI3 kinase/Akt pathway. Taken together, our novel findings suggest that the EDR induced by the strawberry extract was mediated by activation of the PI3 kinase/Akt signaling pathway, resulting in phosphorylation of eNOS.

Nitric Oxide Releasing Metal–Diazeniumdiolate Complexes Strongly Induce Vasorelaxation and Endothelial Cell Proliferation

The preparation, characterization, and NO-releasing properties of metal complexes derived from N-aminoethylpiperazine-N-diazeniumdiolate (HPipNONO), [Cu(PipNONO)Cl] and [Ni(PipNONO)Cl], and the Ni(II) complex derived from the Schiff base between HPipNONO and salicylaldehyde, [Ni(SalPipNONO)], are described. Compounds [Cu(PipNONO)Cl] and [Ni(SalPipNONO)] release NO at a much slower rate than HPipNONO in aqueous buffer in the pH range between 6.8 and 8.0. The kinetics of NO release by [Ni(SalPipNONO)] is complex, with an apparent stepwise release of NO molecules. Both [Cu(PipNONO)Cl] and [Ni(SalPipNONO)] are effective vasorelaxant agents of precontracted rabbit aorta rings, and are active in the nM concentration range. In addition, these complexes promote the proliferation of endothelial cells. Both vascular activities were inhibited by a specific inhibitor of guanylate cyclase, suggesting the involvement of the cGMP pathway. In all biological assays, the reference agent sodium nitroprusside was shown to be 10-1000-fold less potent than the two metal-NONOates.

Sexual dimorphism in rabbit aortic endothelial function under acute hyperglycemic conditions and gender-specific responses to acute 17β-estradiol

Epidemiological data suggest that hyperglycemia abrogates the gender-based cardiovascular protection possibly associated with estrogens. This study was designed to investigate 1) whether rabbit aortic rings show gender differences in the development of abnormal endothelium-dependent vasodilation (EDV) under acute hyperglycemic conditions, 2) the potential role of PKC isoforms and superoxide (O2-) in acute hyperglycemia-induced vascular dysfunction, and 3) the effect of acute estrogen administration on hyperglycemia-induced endothelial dysfunction in male and female rabbits. EDV to ACh was determined before and after 3 h of treatment with high glucose (HG) in phenylephrine-precontracted aortic rings from male and female New Zealand White rabbits. Similar experiments were conducted in the presence of inhibitors of PKC-alpha, PKC-beta, and PKC-delta or an O2- scavenger. The effect of acute estrogen administration was evaluated in the presence and absence of HG. Finally, mRNA expression of PKC isoforms was measured by real-time PCR. We found that 1) 3 h of incubation with HG impairs EDV to a greater extent in female than male aorta, 2) inhibition of PKC-beta or O2- prevents HG-induced impairment of EDV in female aorta, 3) acute 17beta-estradiol aggravates HG-induced endothelial dysfunction in female, but not male, aorta, and 4) PKC-alpha and PKC-beta expression are significantly higher in female than male aorta. This study reveals the predisposition of female rabbit aorta to vascular injury under hyperglycemic conditions, possibly via activation of PKC-beta and O2- production. Furthermore, it suggests that, under hyperglycemic conditions, acute estrogen treatment is detrimental to endothelial function in female rabbits.