Contraction Of Thoracic Aorta Research Articles

Effect of Vitamin K2 on Blood Rheology and Vascular Responses in Diabetic Rats

Background/aim: Diabetes is manifested by endothelial dysfunction and an imbalance between vasoconstriction and vasodilation. The aim of our study is to examine the effect of vitK2 application on vascular and rheological parameters in a rat diabetes model. Materials and methods: A total of 60 male Wistar Albino rats were used to examine vascular responses and hemorheological parameters. A total of 6 groups were: control (C), control+vehicle (Cv), control+vitK2 administered (C + K2), diabetes (D), diabetes+vehicle (Dv), and diabetes+vitK2 (D + K2) group. After the animals were sacrificed, blood and vascular samples were taken and the contraction and relaxation responses of the aorta and erythrocyte deformability and aggregation were examined. Results: When KCl dose-response curves are evaluated; Increased vasoconstriction response was found in the Dv group compared to the Cv group. The increase in vasoconstriction observed in the Dv group decreased with the application of vit K2. D+vitK2 group thoracic aorta contraction responses returned to Cv group levels. In response to increasing cumulative doses of Phe, a significant increase in vasoconstriction response was observed in the Dv group compared to the Cv group. VitK2 application reduced the Phe-mediated contractile response, which was increased in the Dv group, and returned the contraction response to Cv conditions except for two intermediate Phe doses. In the Dv + K2 group, a significant decrease was observed in the aggregation index, which was tended to increase. Conclusion: Considering the cardiovascular complications frequently observed in diabetes, it can be suggested that vitK2 therapy may yield positive outcomes in diabetes.

Perivascular brown adipocytes-derived kynurenic acid relaxes blood vessel via endothelium PI3K-Akt-eNOS pathway.

Several metabolites from the kynurenine pathway of tryptophan metabolism play a critical role in vascular function and vascular wall remodeling. This study aimed to test whether metabolite kynurenic acid (KYNA) from the kynurenine pathway relaxes blood vessels. We employed histological staining, in vitro cell culture, Western blotting, real-time PCR, and nitric oxide detection to validate kynurenine aminotransferase (KAT) localization in the vasculature as well as KYNA action on endothelial cells. We also detected vascular reactivity by organ chamber and monitored blood pressure by telemetry to investigate the regulation effect of KYNA on vascular tone. The results presented that perivascular adipose tissue (PVAT) from mice thoracic aorta had robust staining of anti-KAT1 and KYNA than PVAT from the abdominal aorta and mesenteric artery, which is consistent with the expression profile of brown adipocyte marker uncoupling protein 1. KYNA, metabolized from kynurenine by KAT, relaxed pre-contracted both aortic ring and mesenteric artery. In addition, KYNA derived from KAT in PVAT participates in the cross-talk between PVAT and vessel by mediating PVAT inhibition on agonist-induced thoracic aorta contraction. Furthermore, intraperitoneal injection of KYNA in mice reduced blood pressure. The vessel relaxation effect of KYNA was through the endothelium-dependent PI3K-Akt-eNOS pathway. Finally, the high-fat diet decreased KAT1 expression in perithoracic aortic fat and led to KYNA reduction in blood. Our research identified KYNA generated by KAT as a novel perivascular brown adipocyte-derived vascular relaxation factor and suggests that KYNA reduction is a critical event in vascular dysfunction under obese condition.

Macrovascular Protecting Effects of Berberine through Anti-inflammation and Intervention of BKCa in Type 2 Diabetes Mellitus Rats.

The aim of this study was to examine the effect of berberine on diabetes mellitus in vivo and in vitro, and elucidate the underlying mechanisms. Rat models of type 2 diabetes mellitus (T2DM) were established and were treated with berberine. Pathological changes in the thoracic aorta, and inflammatory factor and adiponectin levels were investigated. Vascular smooth muscle cells (VSMCs) of the thoracic aorta were cultured and treated with berberine. Cellular proliferation, migration, and inflammatory factor levels were investigated. Responses of vascular rings to phenylephrine (PE) and sodium nitroprusside (SNP) after berberine intervention and the changes of relaxation responses to SNP after adding Iberiotoxin (IbTX) were investigated. Berberine ameliorated the pathological status of the thoracic aorta in the T2DM rats. Berberine significantly inhibited the C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) production, and increased the adiponectin level compared with the model group. Compared with the model group, berberine inhibited the proliferation and migration of VSMCs in vitro, and reduced tumor growth factor-β1 (TGF-β1), IL-6, and TNF-α levels. Furthermore, the contraction of thoracic aorta to PE was reduced, while the relaxation response of thoracic aorta to SNP was increased, after the berberine intervention in the T2DM rats. The relaxation response of thoracic aorta to SNP in the model and berberine groups decreased after the IbTX treatment. Protective effects of berberine against macrovascular complications induced by diabetes mellitus may be attributed to inhibiting of the inflammation and intervening of the calcium- activated potassium (BKCa).

APPLICATION OF QUERCETIN FOR CORRECTION OF THE IMPAIRMENT OF THE FUNCTIONAL STATE OF THE ENDOTHELIUS OF VESSELS (CLINICAL AND EXPERIMENTAL STUDY).

in the experiment, to investigate the effect of Quercetin on the NO-dependent reactions of isolated vessels involving endothelium and perivascular adipose tissue (PVAT) after a single X-ray irradiation of rats at a sublethal dose. In a clinical study, to investigate the effect of long-term use of Quercetin on the functional state of themicrovascular endothelium in the elderly patients with metabolic syndrome (MS). Experimental studies were performed on vascular fragments obtained from adult male rats(7-8 months) of the control group, in animals exposed to a single R-irradiation at a dose of 7 Gy and animals irradiated in the same dose, which received Quercetin orally for 14 days three times a week based on 10 mg/kg bodyweight. Fragments of the thoracic aorta (TA) and mesenteric artery (MA) were cleaned of perivascular adipose tissue (PVAT-) or left uncleaned (PVAT+), and then were cut into rings (up to 2 mm). The amplitude of the contractionof the rings TA and MA under the influence of phenylephrine (PE, 3 x 10-6 M), the amplitude of the contraction of therings TA and MA in the presence of a competitive blocker of NO-synthase methyl ester of N-nitro-L-arginine(L-NAME, 10-5 M), the amplitude of relaxation of the rings TA and MA in the presence of N-acetylcysteine (NAC, 10-4 M)were measured. The clinical study examined 110 patients with MS criteria in accordance with ATP III (2001).Patients in the main group for 3 months received Quercetin from the same manufacturer, 80 mg three times a day,patients in the control group received placebo. Single R-irradiation disrupts the regulation of the contractile function of TA and MA, which is evidenced bychanges in the contractile reactions of isolated fragments of these vessels as a response to the action of vasoactivecompounds. Course use of Quercetin in irradiated rats leads to the normalization of contractile and dilatory vascular responses due to partial correction of NO metabolism in the endothelium and PVAT. For the majority of patients(69 %) who received Quercetin, a post-occlusive hyperemia test showed a statistically significant increase of maximal volumetric velocity of the skin blood flow rate and duration of the recovery period to the baseline, which indicates about improvement of vasomotor vascular endothelial function. Course use of Quercetin improves the functional state of the microvascular endothelium among theelderly people with MS, normalizes contractile and dilatory vascular responses in irradiated rats due to partial correction of NO metabolism in the endothelium and PVAT.

Prostaglandin E1 Inhibited Diabetes-Induced Phenotypic Switching of Vascular Smooth Muscle Cells Through Activating Autophagy

Background/Aims: The phenotype switching of vascular smooth muscle cells (VSMCs) was associated with the onset or progression of the atherogenic process in type 2 diabetes mellitus (T2DM). Alprostadil (Prostaglandin E1, PGE1) as a bioactive drug had a protective effect on vascular function. However, it is unknown whether PGE1 inhibited the phenotype switching in VSMCs via autophagy, which played a protective role in the vascular complications of diabetes. Methods: The phenotype switching was induced by high glucose (HG, 25mM) in VSMCs, the protein expression was measured by western blot analysis and immunofluorescent staining. In vivo study, vascular lesion and dysfunction were produced in the rats fed with high fat diet (HFD) combined with low dose streptozotocin (STZ) administration. Results: The decrease of α-SMA and the increase of vimentin, collagen I and proliferating cell nuclear antigen (PCNA) were found in HG-treated VSMCs. Along with more abundance of p62, autophagy markers LC3B and Beclin-1 significantly decreased in VSMCs exposed to HG. Such abnormal changes were significantly reversed by PGE1, which mimicked the role of autophagy activator rapamycin and was dramatically counteracted by 3-methyladenine, an autophagy inhibitor. Furthermore, PGE1 suppressed the phosphorylation of AKT and mTOR, which negatively regulated autophagy level in VSMCs. In vivo study, PGE1 remarkably improved the endothelium-independent contraction of thoracic aorta and restored the expression of α-SMA, osteopontin, LC3B, phosphorylated mTOR in the artery media of T2DM rats. Conclusion: These results demonstrated that PGE1 maintained the phenotype of VSMCs via the AKT/mTOR-dependent autophagy, which prevented diabetes-induced vascular complications.

The Effect of Chronic NO Synthase Inhibition on the Vasoactive and Structural Properties of Thoracic Aorta, NO Synthase Activity, and Oxidative Stress Biomarkers in Young SHR.

Although the role of nitric oxide (NO) in essential hypertension is still unclear, the effects of long-term NO deficiency have not yet been investigated during the critical juvenile period in spontaneously hypertensive rats (SHR). We aimed to analyze the effects of chronic NO synthase (NOS) inhibition on systolic blood pressure (sBP), vasoactivity, morphological changes and superoxide level in the thoracic aorta (TA), NOS activity in different tissues, and general biomarkers of oxidative stress in plasma of young SHR. Four-week-old SHR were treated with NG-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg/day, p.o.) for 4-5 weeks. L-NAME treatment induced a transient sBP increase only, and surprisingly, slightly inhibited endothelium-dependent relaxation of TA. Hereby, the inhibition of NOS activity varied from tissue to tissue, ranging from the lowest in the TA and the kidney to the highest in the brain stem. In spite of an increased sensitivity of adrenergic receptors, the maximal adrenergic contraction of TA was unchanged, which was associated with changes in elastin arrangement and an increase in wall thickness. The production of reactive oxygen species in the TA was increased; however, the level of selected biomarkers of oxidative stress did not change. Our findings proved that the TA of young SHR responded to chronic NO deficiency by the development of adaptive mechanisms on the functional (preserved NO-derived vasorelaxation, unincreased contraction) and molecular (preserved NOS activity) level.

The triterpenoid alpha, beta-amyrin prevents the impaired aortic vascular reactivity in high-fat diet-induced obese mice.

To characterize the protective effects of the triterpenoid mixture alpha, beta-amyrin (AMY, 20mg/kg, during 15days) on the reactivity of isolated aorta of high-fat diet (HFD)-induced obese mice. Male Swiss mice were fed with HFD or normal diet (ND) for 15weeks. Contractions of thoracic aorta in response to KCl or phenylephrine (PHE) and relaxation by acetylcholine (ACh) or sodium nitroprusside (SNP) were analyzed. HFD-fed mice developed hyperglycemia, hyperlipidemia, and significant body weight gain, parameters prevented by AMY treatment. Whereas aortic contractility did not differ in response to KCl, contractions induced by PHE (1μM) as well as relaxation induced by ACh (1-30μM) or SNP (1nM-0.1mM) on PHE-contracted aorta were decreased (p<0.05) in tissues of HFD compared to ND mice, phenomenon significantly (p<0.05) diminished in HFD mice treated with AMY. The relaxant actions of ACh and SNP were inhibited (p<0.05) by tetraethylammonium (TEA, 5mM), apamin (0.1μM), and 4-aminopyridine (4-AP; 3mM) in aortae from ND group, but not from HFD. Treatment of HFD mice with AMY rescued the inhibitory effect of TEA (p<0.05) on vasorelaxant actions of ACh and SNP. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) inhibited similarly the relaxant effects of SNP in all groups. 8-Br-cGMP relaxed with similar profile aortae of all groups. By preventing HFD-induced obesity in mice, AMY rescued the blunted contractile response to PHE, and the attenuated vasorelaxation and K+ channel activation (opening) induced by ACh and SNP in isolated aorta.

Different vasoactive effects of chronic endothelial and neuronal NO-synthase inhibition in young Wistar rats.

While the unequivocal pattern of endothelial nitric oxide synthase (eNOS) inhibition in cardiovascular control is recognized, the role of NO produced by neuronal NOS (nNOS) remains unclear. The aim of this study was to compare the effects of chronic treatment with 7-nitroindazole (7-NI, nNOS inhibitor) and N(G)-nitro-L-arginine methylester (L-NAME, general and predominantly eNOS inhibitor) on cardiovascular system of young normotensive rats. Wistar rats (4 weeks old) were used: controls and rats administered either 7-NI (10 mg/kg bw/day) or L-NAME (50 mg/kg bw/day) in drinking water for 6 weeks. The systolic blood pressure (sBP) was measured by plethysmographic method, and the vasoactivity of isolated arteries was recorded. 7-NI-treatment did not affect sBP; however, the sBP was increased after L-NAME-treatment. L-NAME inhibited acetylcholine-induced relaxation of thoracic aorta (TA), whereas it remained unchanged after 7-NI-treatment. The response of TA to sodium nitroprusside was increased in both experimental groups. The expression of eNOS and nNOS in TA was unchanged in both experimental groups, whereas the activity of NOS was decreased in L-NAME-treated group. Noradrenaline- and angiotensin II-induced contractions of TA were reduced in L-NAME-treated group; however, the contractions remained unchanged in 7-NI-treated group. In all groups, the endogenous angiotensin II participated in adrenergic contraction of TA; this contribution was significantly increased in L-NAME-treated group. Neurogenic contractions in mesenteric artery (MA) remained unchanged after 7-NI-treatment, but increased after L-NAME-treatment. Results show that NO deficiency induced by administration of 7-NI and L-NAME had different cardiovascular effects: eNOS and nNOS triggered distinct signaling pathways in young normotensive rats.

Effect of sufentanil on contraction and anti peroxidative ability of thoracic aorta isolated from rats with diabetes mellitus

Objective To investigate the effect of sufentanil on contraction and anti peroxidative ability of thoracic aorta isolated from rats with diabetes mellitus.Methods Eight male rats with diabetes were decapitated and their thoracic aorta were i solated.The aortic rings obtained from diabetes rat were divided into 4 groups(n=8):control group and 3 sufentanil groups (7×10-11,2×10-10,1×10-9 mol/L).Vitro vascular experimental method was used to observe the effect of different concentrations of sufentanil on the norepinephrine(NE)-induced contraction of thoracic aorta from diabetic rats and the content of nitrogen monoxide(NO),maleic dialdehyde(MDA) and superoxide dismutase(SOD) on the vascular ring.Results The contraction amplitude of 3 sufentanil groups was orderly (25.4±4.0)％,(21.3±3.5)％ and (17.4±2.4)％.The SOD activity of 3 sufentanil groups was orderly (3.8±1.2),(4.9±0.8) U/mgprot and (6.1±0.3) U/mgprot.The contraction amplitude of thoracic aorta from 3 sufentanil groups was significantly lesser than that from control group,the level of SOD activity was higher in 3 sufentanil groups than in control group.Sufentanil significantly inhibited the NE-induced aortic contraction and changed the SOD activity in proportion to concentration.Conclusions Sufentanil can inhibit NE-induced contraction and change the anti peroxidative ability of thoracic aorta isolated from rats with diabetes mellitus in a concentration-dependent manner. Key words: Sufentanil; Diabetes mellitus; Nitrogen monoxide; Maleic dialdehyde; Superoxide dismutase

Metastatic breast carcinoma induces vascular endothelial dysfunction in Balb-c mice: Role of the tumor necrosis factor-α and NADPH oxidase

Although the oxidative stress and inflammation are closely related with breast cancer, there is no study directly examining the possible changes in vascular functions in the presence of breast carcinoma. The goal of the present study was to evaluate changes in vascular reactivity in tumor-bearing mice. In this study, highly metastatic breast carcinoma cells which were derived from liver or brain metastasis of 4T1 murine breast carcinoma (4TLM and 4TBM, respectively), and 67NR cells which were tumorigenic but non-metastatic cells were used. Female Balb-c mice 8–10weeks old were divided into following groups: (1) control, (2) injected with 67NR, (3) injected with 4TLM, and (4) injected with 4TBM orthotopically. Thoracic aorta was removed 23–25days after injection of tumor cells. Isometric tension studies were performed in response to potassium chloride (KCl), phenylephrine (Phe), acetylcholine (ACh, an endothelium-dependent vasodilator), and sodium nitroprusside (SNP, an endothelium-independent vasodilator). Endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (Ser 1177) (p-eNOS), gp91phox, and tumor necrosis factor-α (TNF-α) expressions in aortic tissues were demonstrated by immunohistochemistry. The level of TNF-α in vascular tissue was measured by ELISA. The presence of tumor was resulted in significant inhibition of response to ACh in both 4TLM and 4TBM injected mice, but not 67NR injected mice. Furthermore, both KCl and Phe-induced contraction of thoracic aorta was not changed significantly in tumor-bearing animals. eNOS and p-eNOS expressions decreased while gp91phox and TNF-α expressions increased in endothelium of 4TLM and 4TBM mice compared to 67NR injected and control mice. Moreover, TNF-α levels of thoracic aorta in mice with metastatic breast carcinoma were significantly higher than that of 67NR mice. Tumor-induced endothelial dysfunction determined by ACh-induced relaxation improved by superoxide dismutase (SOD), apocynin (a NADPH oxidase inhibitor), and infliximab (a TNF-α monoclonal antibody). The findings of this study suggest that the presence of metastatic breast carcinoma may cause a significant reduction in endothelium-dependent relaxation of thoracic aorta via NADPH oxidase-mediated oxidative stress and TNF-α production.

Study on vasodilatation effects of total flavonoid from polygonum aviculare on blood vessel of rat in vitro

Objective To investigate the vasodilatation effects of total flavonoid from polygonum aviculare on rat thoracic aorta and its underlying mechanisms. Methods Total flavonoid from polygonum aviculare was gotten by extracted with 65% alcohol, gathered with polyamide, and eluted with 75% alcohol. The content of flavone was determined with rutoside as standard preparation. Normal rats thoracic aorta in vitro used as sample, BL-420E biological functional experiment system was utilized to record dilatation effect of total flavonoid on PE affecting pre-contracting blood vessel and the relation between dilatation effect of total flavonoid on blood vessel and calcium influx. Results Total flavonoids from polygonum aviculare can diastole contractions of thoracic aorta caused by PE. In calcium-free perfusion, gradually adding CaCl2 induced calcium influx. Clinical data showed dose-effect relation between drug and blood vessel contraction decreased in the total flavonoids from polygonum aviculare incubation rats than normal rats. Besides, total flavonoids from polygonum aviculare can obviously inhibit contraction of blood vascular circle induced by calcium releasing. Conclusion FP exerted a dose-dependent vasodilatation effect on rat isolated aorta rings by inhibiting Ca2＋ influx via L-type voltage-gated Ca2＋ channels and Ca2＋ release from sarcoplasmic reticulum, consequently decrease Ca2＋ in vascular smooth muscle cells. Key words: Polygonum aviculare; Total flavone; Hypertension; Vasodilation

Effect of sufentanil on norepinephrine-induced contraction of thoracic aorta isolated from rats with spontaneous hypertension

Objective To investigate the effect of sufentanil on norepinephrine (NE)-induced contraction of thoracic aorta isolated from rats with spontaneous hypertension (SH) .Methods Eight male rats with SH weighing 250-300 g were used in this study. The rats were decapitated and their thoracic aortas were isolated and cut into rings 2-3 mm in length. The aorta rings were suspended for isometric tension recording. The aortic rings obtained from SH rats were divided into 4 groups ( n = 8 each) : control group and 3 sufentanil groups. The contraction of aortic rings in response to NE in the absence (control) and presence of 3 concentrations of sufentanil 7 × 10-11 ,2 × 10-10 and 1 × 10-9 mol/L was recorded. Results The amplitude of NE-induced contraction of thoracic aorta was significantly greater in 3 sufentanil groups than in control group. Sufentanil significantly inhibited the NE-induced aortic contration in proportion to concentration. Conclusion Sufentanil can inhibit NE-induced contraction of thoracic aorta isolated from rats with SH in a concentration-dependent manner. Key words: Sufentanil; Norepinephrine; Hypertension; Aorta,thoracic

Paraoxon Attenuates Vascular Smooth Muscle Contraction through Inhibiting Ca2+Influx in the Rabbit Thoracic Aorta

We investigated the effect of paraoxon on vascular contractility using organ baths in thoracic aortic rings of rabbits and examined the effect of paraoxon on calcium homeostasis using a whole-cell patch-clamp technique in isolated aortic smooth muscle cells of rabbits. The findings show that administration of paraoxon (30 μM) attenuated thoracic aorta contraction induced by phenylephrine (1 μM) and/or a high K+ environment (80 mM) in both the presence and absence of thoracic aortic endothelium. This inhibitory effect of paraoxon on vasoconstrictor-induced contraction was abolished in the absence of extracellular Ca2+, or in the presence of the Ca2+ channel inhibitor, verapamil. But atropine had little effect on the inhibitory effect of paraoxon on phenylephrine-induced contraction. Paraoxon also attenuated vascular smooth muscle contraction induced by the cumulative addition of CaCl2 and attenuated an increase of intracellular Ca2+ concentration induced by K+ in vascular smooth muscle cells. Moreover, paraoxon (30 μM) inhibited significantly L-type calcium current in isolated aortic smooth muscle cells of rabbits. In conclusion, our results demonstrate that paraoxon attenuates vasoconstrictor-induced contraction through inhibiting Ca2+ influx in the rabbits thoracic aorta.

Imperatorin is responsible for the vasodilatation activity of Angelica Dahurica var. Formosana regulated by nitric oxide in an endothelium-dependent manner

To demonstrate the vasodilatation activity of the coumarin-containing Angelica dahurica var. formosana and to further analyze active components in the herb extracts. (1) The vasodilatation effects induced by different extracts (cyclohexane, ethyl acetate, acetone, methanol, 95 % ethanol and water) of Angelica dahurica var. formosana on mouse thoracic aorta pre-contracted with phenylephrine were investigated. (2) The amount of imperatorin and isoimperatorin in each extract was measured by high-performance liquid chromatography. (3) The vasodilatation effects of imperatorin and isoimperatorin on mouse thoracic aorta were compared using the same in vitro method. (4) The vasodilatation mechanism of imperatorin in the mouse thoracic aorta pre-contracted with phenylephrine was studied using the methods of denuded endothelium, NG-nitro-L-arginine methylester (L-NAME, a nitric oxide synthase inhibitor), and propranolol. (1) The cyclohexane and ethyl acetate extracts of Angelica dahurica var. formosana decreased the maximal response of phenylephrine-induced mouse thoracic aorta contraction dose-dependently, with 50% inhibiting concentration (IC(50)) values of 35.3+/-12.4 mg/L and 40.5+/-12.0 mg/L, respectively. The vasodilatation effect of imperatorin and isoimperatorin was dose-dependent. (2) The cyclohexane extract, showing the strongest vasodilatation effect, possessed the highest contents of imperatorin (4.09%) and isoimperatorin (0.27%, w/w). There was a correlation between the vasodilatation activity and the contents of imperatorin and isoimperatorin in the extracts. (3) The vasodilatation effect of imperatorin was about 4-fold stronger than that of isoimperatorin. (4) The vasodilatation effect of imperatorin was signifificantly attenuated to 24.88%+/-4.06% in the denuded endothelium group compared with the intact endothelium group. And 1 mmol/L L-NAME reduced the imperatorin-induced vasorelaxation by 32.18 %+/-11.29 %. The principal effective component of Angelica dahurica var. Formosana was found to be imperatorin. Imperatorin-induced vasodilatation is at least partially regulated by nitric oxide, and has no correlation to beta-receptor.

RGS5, RGS4, and RGS2 expression and aortic contractibility are dynamically co-regulated during aortic banding-induced hypertrophy

Overexpression of regulator of G protein signaling 5 (RGS5) in arteries over veins is the most striking difference observed using microarray analysis. The obvious question is what arterial function might require RGS5. Based on functions of homologous proteins in regulating cardiac mass and G-protein-coupled receptor (GPCR) signaling, we proposed that RGS5 and vascular expressed RGS2 and RGS4 could participate in regulating arterial hypertrophy. We used the suprarenal abdominal aorta banding model to induce hypertension and hypertrophy. All 3 RGS messages were expressed in unmanipulated aorta with RGS5 predominating. After 2 days, thoracic aorta lost expression of RGS5, 4, and 2. At 1 week, all three returned to normal, and at 28 days, they increased many fold above normal. Valsartan blockade of angiotensin II (angII)/angII type 1 receptor signaling prevented upregulation of RGS messages but only delayed mass increases, implying wall mass regulation involves both angII-dependent and angII-independent pathways. The abdominal aorta showed less dramatic expression changes in RGS5 and 4, but not 2. Again, those changes were delayed by valsartan treatment with no mass changes. Thoracic aorta contraction to GPCR agonists was examined in aortic explant rings to identify vessel wall physiological changes. In 2-day aorta, the response to Gαq/i agonists increased above normal, while 28-day aorta had attenuated induced contraction via Gαq/i agonist, implicating a connection between RGS message levels and changes in GPCR-induced contraction. In vitro overexpression studies showed RGS5 inhibits angII-induced signaling in smooth muscle cells. This study is the first experimental evidence that changes in RGS expression and function correlate with vascular remodeling.

Functional and structural pattern of arterial responses in hereditary hypertriglyceridemic and spontaneously hypertensive rats

It has been shown that endothelium-derived nitric oxide (NO) plays an important role in regulation of vascular tone in the prenatal and early postnatal period. The aim of this paper was to determine the reactivity and accompanying structural changes in thoracic aorta from 4-week-old spontaneously hypertensive rats (SHR) and rats with hereditary hypertriglyceridemia (hHTG) in comparison with age-matched normotensive controls. For functional studies thoracic aorta was excised, cut into rings and mounted in organ baths for measurement of isometric contractile force. For morphological studies cardiovascular system of rats was perfused with glutaraldehyde fixative (at 100 mm Hg) via cannula placed in the left ventricle. Morphological changes of thoracic aorta were measured using light microscopy. Systolic blood pressure (SBP) in SHR (98+/-1 mm Hg) did not significantly differ from that of age-matched control rats (95+/-4 mm Hg), but was slightly increased in hHTG rats (110+/-2 mm Hg, P&lt;0.05). Heart weight/body weight ratio was higher in SHR and hHTG rats than in control group indicating the hypertrophy of the heart in both models of hypertension. Endothelium-dependent relaxation of aorta induced by acetylcholine was preserved in all groups and did not differ from that in control normotensive rats. The maximal isometric contraction of thoracic aorta to noradrenaline (NA) was reduced in hypertensive groups and the concentration-response curves to NA were shifted to the right indicating increased sensitivity of smooth muscle to NA. The values of wall thickness and cross sectional area as well as inner diameter of thoracic aorta in SHR and hHTG rats were significantly decreased in comparison to control groups. Endothelial dysfunction seems to be absent in all young rats before development of hypertension. In conclusion, our observations indicate that in early stage of experimental hypertension NO-dependent relaxation is preserved so that putative impairment of this function provides no significant pathogenic contribution to the onset of hypertension in these two experimental models.

In vitro and in vivo characterization of a novel naphthylamide ATP-sensitive K+ channel opener, A-151892.

1. Openers of ATP-sensitive K(+) channels are of interest in several therapeutic indications including overactive bladder and other lower urinary tract disorders. This study reports on the in vitro and in vivo characterization of a structurally novel naphthylamide N-[2-(2,2,2-trifluoro-1-hydroxy-1-trifluoromethyl-ethyl)-naphthalen-1-yl]-acetamide (A-151892), as an opener of the ATP-sensitive potassium channels. 2. A-151892 was found to be a potent and efficacious potassium channel opener (KCO) as assessed by glibenclamide-sensitive whole-cell current and fluorescence-based membrane potential responses (-log EC(50)=7.63) in guinea-pig bladder smooth muscle cells. 3. Evidence for direct interaction with KCO binding sites was derived from displacement of binding of the 1,4-dihydropyridine opener [(125)I]A-312110. A-151892 displaced [(125)I]A-312110 binding to bladder membranes with a -log Ki value of 7.45, but lacked affinity against over 70 neurotransmitter receptor and ion channel binding sites. 4. In pig bladder strips, A-151892 suppressed phasic, carbachol-evoked and electrical field stimulus-evoked contractility in a glibenclamide-reversible manner with -log IC(50) values of 8.07, 7.33 and 7.02 respectively, comparable to that of the potencies of the prototypical cyanoguanidine KCO, P1075. The potencies to suppress contractions in thoracic aorta (-log IC(50)=7.81) and portal vein (-log IC(50)=7.98) were not substantially different from those observed for suppression of phasic contractility of the bladder smooth muscle. 5. In vivo, A-151892 was found to potently suppress unstable bladder contractions in obstructed models of unstable contractions in both pigs and rats with pED(35%) values of 8.05 and 7.43, respectively. 6. These results demonstrate that naphthylamide analogs exemplified by A-151892 are novel K(ATP) channel openers and may serve as chemotypes to exploit additional analogs with potential for the treatment of overactive bladder and lower urinary tract symptoms.

Influence of lead on rat thoracic aorta contraction and relaxation

Low levels of lead, but not high levels, produce hypertension. This mystery has not yet been resolved. In this study we compared the in vitro vasoresponsiveness in rat thoracic aorta to low dose (10 −8 mol/L) and high dose (10 −5 mol/L and 10 −4 mol/L) lead acetate. In addition to the direct response to lead, we examined reactivity to norepinephrine, acetylcholine, isoproterenol, phorbol ester, and calcium in the presence and absence of lead. Neither low-dose nor high-dose lead directly affected aortic contractile or relaxant responses. However, lead, only at the highest concentration (10 −4 mol/L), increased the contractions to calcium at all submaximal calcium concentrations. We conclude that low-dose lead must increase blood pressure indirectly through a humoral effect. The reasons for the failure of high-dose lead to influence blood pressure remain to be explored.

2APB, 2-aminoethoxydiphenyl borate, a membrane-penetrable modulator of Ins(1,4,5)P3-induced Ca2+ release.

The effects of a novel membrane-penetrable modulator, 2APB (2-aminoethoxy diphenyl borate), on Ins(1,4,5)P3-induced Ca2+ release were examined. 2APB inhibited Ins(1,4,5)P3-induced Ca2+ release from rat cerebellar microsomal preparations without affecting [3H]Ins(1,4,5)P3 binding to its receptor. The IC50 value (concentration producing 50% inhibition) of 2APB for inhibition of Ins(1,4,5)P3 (100 nM) induced Ca2+ release was 42 microM. Further increase in the concentration of 2APB (more than 90 microM) caused a gradual release of Ca2+ from cerebellar microsomal preparations. Addition of 2APB to the extracellular environment inhibited the cytosolic Ca2+ ([Ca2+]c) rise in intact cells such as human platelets and neutrophils stimulated by thromboxane-mimetic STA2 or thrombin, and leukotriene B4 (LTB4) or formyl-methionine-leucine-phenylalanine (FMLP), respectively. 2APB inhibited the contraction of thoracic aorta isolated from rabbits induced by angiotensin II (AII), STA2, and norepinephrine in a non-competitive manner, but showed no effect on the contraction of potassium-depolarized muscle. 2APB had no effect on the Ca2+ release from the ryanodine-sensitive Ca2+ store prepared from rat leg skeletal muscle and heart. Although the specificity of 2APB with respect to the intracellular signaling system was not fully established, 2APB is the first candidate for a membrane-penetrable modulator of Ins(1,4,5)P3 receptor, and it should be a useful tool to investigate the physiological role of the Ins(1,4,5)P3 receptor in various cells.

Contraction and relaxation of aortas from galactosaemic rats and the effects of aldose reductase inhibition

Rats were fed for 10 days with a 40% galactose diet, in order to chronically stimulate the polyol pathway. Thoracic aorta contraction and relaxation were studied. Compared to controls, galactosaemia did not influence contractions to phenylephrine or serotonin. Acetylcholine produced concentration-dependent relaxation of aortic rectangles precontracted with phenylephrine; galactosaemia caused a 25% deficit in maximum relaxation to acetylcholine (P < 0.01) and a 168% increase in EC 50. There was a similar 25% reduction in relaxation to 3 μM calcium ionophore A23187 (P < 0.05). By contrast, there were no significant differences in endothelium-independent relaxation to nitroglycerine or cromakalim. The abnormalities in endothelium-dependent relaxation were completely prevented by treating galactosaemic rats with the aldose reductase inhibitor, ponalrestat. Thus, the data demonstrate that elevated polyol pathway activity contributes to reduced endothelium production, release or the action of nitric oxide in experimental galactosaemia, and suggest that this mechanisms could also contribute to the vascular defects seen in diabetes mellitus.