Internal Mammary Artery Rings Research Articles

The effects of sugammadex on isolated human internal mammary artery and saphenous vein rings.

The effects of sugammadex on isolated human internal mammary artery and saphenous vein rings.

Trace amine-induced vasoconstriction of human mammary artery and saphenous vein

Sympathomimetic amines, including β-phenylethylamine (PEA), constrict animal blood vessels but their mechanism of action is not now thought to be through α-adrenoceptors and release of noradrenaline but via trace amine-associated receptors (TAARs). This information is not available for human blood vessels. Functional studies were therefore performed on human arteries and veins to establish whether they constrict to PEA and whether any constrictions are adrenoceptor-mediated. Isolated internal mammary artery or saphenous vein rings were set up in Kreb's-bicarbonate solution at 37 ± 0.5 °C gassed with O2:CO2 (95:5) under class 2 containment. Isometric contractions were measured and cumulative concentration-response curves for PEA or the α-adrenoceptor agonist, phenylephrine were established. PEA showed concentration-related contractions. The maximum was significantly greater in arteries (1.53 ± 0.31 g, n = 9) than veins (0.55 ± 0.18 g, n = 10), but not when plotted as % of KCl contractions. PEA showed slowly developing contractions plateauing at 17,3 ± 3.7 min in mammary artery. The reference α-adrenoceptor agonist, phenylephrine, exhibited more rapid onset (peak 5.0 ± 1.2 min) but non-sustained contractions. In saphenous veins, PEA (62.8 ± 10.7%) and phenylephrine (61.4 ± 9.7%, n = 4) displayed the same maximum, but phenylephrine was more potent. The α1-adrenoceptor antagonist, prazosin (1 μM), blocked phenylephrine contractions of mammary arteries but not PEA contractions in either vessel. PEA causes substantial vasoconstriction of human saphenous vein and mammary artery, which explains its vasopressor actions. This response, however, was not mediated via α1-adrenoceptors, but likely due to TAARs. The classification of PEA as a sympathomimetic amine on human blood vessels is therefore no longer valid and requires revision.

The effects of botulinum toxin A and papaverine on human saphenous vein and internal mammary artery grafts: an in vitro study.

Autologous saphenous vein (SV) and internal mammary artery (IMA) are used as bypass conduits during coronary artery bypass graft surgery. Vasospasm of the arterial and venous grafts may constitute a significant clinical problem. Pretreatment with a vasodilator drug of the graft ex vivo or intraluminal injection before implantation may be used for spasm prophylaxis. This in vitro study was designed to assess the vasoactive effects and time-dependent changes of botulinum toxin A (BTX-A) and papaverine pretreatment on vasospasm of human SV and IMA grafts. Also, histomorphology of the vessels was assessed. SV and IMA segments were suspended in organ baths, and isometric contraction responses to 2 different concentrations of 5-hydroxytryptamine (5-HT) and endothelin-1 (ET-1) were recorded after incubation with 2 different concentrations of BTX-A and papaverine at 2 time points (0 h and 2 h). The results revealed the following: 1) incubation with BTX-A and papaverine relaxes both SV and IMA rings contracted with 5-HT and ET-1; 2) the duration of the relaxant effect of BTX-A lasts longer than papaverine; and 3) no apparent histomorphological changes were observed in the grafts under light microscopy. This study demonstrates that in human SV and IMA grafts, pretreatment with both BTX-A and papaverine are safe and have a potent inhibitory effect depending on the vessel and vasoconstrictor agent. The long-lasting vasodilatory effect of BTX-A on vascular smooth muscle may provide promising results in the prevention of venous and arterial graft spasm.

Effect of RhoA/Rho‐kinase inhibitor in Human Internal Mammary Artery and Clinical Implications

ObjectivesCoronary artery bypass grafting surgery (CABG) is the treatment of choice for severe coronary artery disease (CAD). Graft failure is a common complication after CABG. Different biological mechanisms contribute to the pathophysiology of vascular graft failure including vasospasm. RhoA/Rho‐kinase (ROCK) pathway plays an important role in cell contraction of cardiovascular disease. ROCK is a downstream effector of small GTP‐binding protein RhoA and has two isoforms, ROCK1 and ROCK2. This study aimed to investigate the inhibitory effect of ROCK inhibitor fasudil on the vasoconstriction in human internal mammary artery (IMA) from patients undergoing CABG and to explore whether the combination of fasudil and nitroglycerin (NTG) is superior than being used alone.MethodsIsolated human IMA rings (n=8 in each experimental group) taken from 58 patients undergoing CABG were studied in myograph. Cumulative concentration‐relaxation curves for fasudil (−9 to −3.5 log M) were established in IMA precontracted with KCl (30 mM) and U46619 (−8 log M). Cumulative concentration‐contraction curves for KCl (5 to 120 mM) and U46619 (−9 to −4.5 log M) were also established in two ways: (1) in three groups pretreated with the plasma concentration (−6.3 log M) and 10‐fold higher concentration of fasudil (−5.3 log M) or vehicle to estimate the depression effect of fasudil; (2) in four groups pretreated with fasudil (−6.3 log M), NTG (0.1 μM), the combination, and vehicle for 40 minutes. Western Blot was used to measure the change of the ROCK2 protein.ResultsFasudil caused similar cumulative relaxation in KCl‐ or U46619‐ contracted (p > 0.05) rings. Pretreatment with −5.3 log M fasudil significantly depressed subsequent contraction by KCl (P < 0.01 vs. control, P < 0.05 vs. −6.3 log M) and U46619 (P < 0.05 vs. control or −6.3 log M). Pretreatment with the combination of NTG and fasudil significantly depressed the cumulative contraction by KCl (P < 0.01 vs. control; P < 0.05 vs. −5.3 log M; P < 0.01 vs. NTG). Similarly, in U46619‐induced contraction, the combination also significantly depressed the contraction (P < 0.001 vs. control; P < 0.05 vs. −5.3 log M fasudil; P < 0.01 vs. NTG). Fasudil also caused a decrease of ROCK2 protein content (p < 0.05).ConclusionsFasudil has a potent inhibitory effect on the vasoconstriction mediated by KCl and U46619 in human conduit arteries. Combination of fasudil and NTG is more effective than fasudil or NTG alone. These findings provide a new antispastic method in CABG and may be beneficial to long‐term patency of the grafts.Support or Funding InformationThis work was supported by the National Natural Science Foundation of China [81870288 & 81870227]; the Non‐profit Central Research Institute Fund of Chinese Academy of Medical Sciences [2019XK310001 & 2018TX31002]; Tianjin Science and Technology Committee[18PTZWHZ00060];Binhai New Area Health Bureau (2016BWKY007 & 2018BWKZ005).

EPA:DHA 6:1 is a superior omega-3 PUFAs formulation attenuating platelets-induced contractile responses in porcine coronary and human internal mammary artery by targeting the serotonin pathway via an increased endothelial formation of nitric oxide

At arterial sites of endothelial denudation and dysfunction, activated platelets contribute to vascular injury through the release of potent contracting factors such as serotonin (5-HT). This study evaluated whether omega-3 polyunsaturated fatty acids (PUFAs), known to protect the vascular system, are able to prevent platelets-induced contractile responses in isolated arteries and, if so, to investigate the underlying mechanism and the importance of the omega-3 PUFAs formulation.Porcine coronary arteries (PCA), human internal mammary arteries (IMA) and washed human platelets were prepared and vascular reactivity was studied in organ chambers.In PCA rings, aggregating platelets caused concentration-dependent contractions that were significantly inhibited by the 5-HT2A receptor antagonist ketanserin, and by EPA:DHA 6:1 but not EPA:DHA 1:1 at 0.4% v/v. EPA:DHA 6:1 also prevented the 5-HT-induced contractions but affected only slightly those to the thromboxane A2 analogue U46619. The inhibitory effect of EPA:DHA 6:1 on platelets-induced contractions was not observed in rings without endothelium, and prevented by an eNOS inhibitor but not by inhibitors of endothelium-dependent hyperpolarization. In IMA rings, EPA:DHA 6:1 but not EPA:DHA 1:1 at 0.4% v/v significantly prevented the 5-HT-induced contraction, and induced greater endothelium-dependent relaxations than bradykinin and acetylcholine sensitive to an eNOS inhibitor.EPA:DHA 6:1 strongly inhibits platelets- and 5-HT-induced contractions in PCA rings and those to 5-HT in IMA rings most likely through an increased endothelial formation of NO. These findings suggest that the omega-3 PUFAs EPA:DHA 6:1 formulation may be of interest to prevent platelets-induced vascular injury at arterial sites of endothelial dysfunction.

Propofol-Induced Vasodilation in Human Internal Mammary Artery: Role of Potassium Channels

The aim of this study was to investigate the vascular effects and mechanisms of propofol in the human internal mammary artery (IMA). In vitro experimental study. The study was conducted inthe research laboratory of a pharmacology department. IMA segments were obtained from 52 patients undergoing coronary artery bypass surgery. The IMA rings were suspended in isolated organ baths, and the changes in the tension were isometrically recorded. The antagonistic effect of propofol (1 μM, 10 μM, and 100 μM) on contractions induced by potassium chloride (45 mM), phenylephrine (1 μM), 5-hydroxytryptamine (30 μM), and calcium chloride (10 μM-10 mM) was investigated. The relaxations induced by propofol also were tested in the presence of the nitric oxide synthase inhibitor, nitro-L-arginine methyl ester (100 mM); the cyclooxygenase inhibitor, indomethacin (10 mM); and the potassium ion channel inhibitors, tetraethylammonium (1 mM), iberiotoxin (20 nM), glibenclamide (10 µM), 4-aminopyridine (1 mM), and barium chloride (30 µM). Propofol caused a significant concentration-dependent vasorelaxation, which was endothelium independent. It inhibited the contractions induced by potassium chloride, phenylephrine, 5-hydroxytryptamine, and calcium chloride (p < 0.001), but it did not affect the basal tension. Propofol-induced relaxation was significantly inhibited by iberiotoxin and tetraethylammonium (p < 0.001); however, it was not affected by 4-aminopyridine, glibenclamide, and barium chloride. This study clearly reveals that propofol relaxes the IMA, and propofol-induced vasodilation may be related to large conductance calcium ion-activated potassium ion channel activation. Propofol use in coronary artery bypass surgery can be valuable via its favorable vasodilator effect to overcome perioperative vasospasm of IMA.

Ghrelin Preserves Ischemia-Induced Vasodilation of Male Rat Coronary Vessels Following β-Adrenergic Receptor Blockade.

Acute myocardial infarction (MI) triggers an adverse increase in cardiac sympathetic nerve activity (SNA). Whereas β-adrenergic receptor (β-AR) blockers are routinely used for the management of MI, they may also counter β-AR-mediated vasodilation of coronary vessels. We have reported that ghrelin prevents sympathetic activation following MI. Whether ghrelin modulates coronary vascular tone following MI, either through the modulation of SNA or directly as a vasoactive mediator, has never been addressed. We used synchrotron microangiography to image coronary perfusion and vessel internal diameter (ID) in anesthetized Sprague-Dawley rats, before and then again 30 minutes after induction of an MI (left coronary artery ligation). Rats were injected with either saline or ghrelin (150 µg/kg, subcutaneously), immediately following the MI or sham surgery. Coronary angiograms were also recorded following β-AR blockade (propranolol, 2 mg/kg, intravenously). Finally, wire myography was used to assess the effect of ghrelin on vascular tone in isolated human internal mammary arteries (IMAs). Acute MI enhanced coronary perfusion to nonischemicregions through dilation of small arterioles (ID 50 to 250 µm) and microvessel recruitment, irrespective of ghrelin treatment. In ghrelin-treated rats, β-AR blockade did not alter the ischemia-induced vasodilation, yet in saline-treated rats, β-AR blockade abolished the vasodilation of small arterioles. Finally, ghrelin caused a dose-dependent vasodilation of IMA rings (preconstricted with phenylephrine). In summary, this study highlights ghrelin as a promising adjunct therapy that can be used in combination with routine β-AR blockade treatment for preserving coronary blood flow and cardiac performance in patients who suffer an acute MI.

Blood transfusions may impair endothelium-dependent vasodilatation during coronary artery bypass surgery

ObjectiveThe hemolytic product free-hemoglobin (fHb) reduces nitric oxide (NO) bioavailability. The present study aims to establish whether administration of different blood transfusions result in increased circulating fHb levels and NO consumption with effects on arterial NO-dependent blood flow in patients undergoing CABG surgery. MethodsNinety-five consecutive patients undergoing elective CABG surgery were prospectively divided in four groups based on blood transfusion requirements during surgery: stored blood cells (SBC, n. 21), intraoperative autologous salvaged blood (ASB, n. 25), SBC and ASB (n.22), no transfusion (control, n. 27).Blood samples were collected before and after intervention to analyse plasma levels of fHb and NO consumption. Endothelium-dependent relaxation was assessed in left internal mammary artery (LIMA) rings harvested before chest closure. Peripheral artery tonometry was assessed after intervention. ResultsTransfusions with SBC increased plasma fHb (p<0.05). Transfusions of ASB resulted in higher plasma fHb compared to SBC (p<0.01). fHb concentrations directly correlated with NO consumption (r=0.65, p<0.001). Maximal endothelium-dependent relaxation in LIMA was significantly attenuated in SBC and ASB patients compared to control (15.2±3.1% vs 21.1±2.5% vs 43±5.0% respectively; p<0.01). Significant correlations were identified between the aortic pressure wave velocity, plasma fHb concentration and NO consumption (p<0.01). ConclusionsIntraoperative blood transfusions and particularly autologous salvaged blood impair endothelium-dependent relaxation through NO scavenging by fHb. These findings obtained in vitro and in vivo provide new insights into the adverse relation between blood transfusions and patient outcome.

Non‐adrenergic Vasoconstriction of Human Blood Vessels to the Trace Amine, β‐Phenylethylamine

Trace amines, such as β‐phenylethylamine (PEA), cause vasoconstriction in animal blood vessels not by indirect sympathomimetic actions but via trace amine‐associated receptors (TAARs). Functional studies were therefore performed on human arteries and veins surplus to coronary artery by‐pass graft (CABG) surgery to establish whether they constrict to PEA and if so whether they are adrenoceptor‐mediated. Internal mammary artery or saphenous vein rings were set up in organ baths containing Kreb's bicarbonate solution at 37±0.5°C gassed with O2:CO2 (95:5) under class 2 containment conditions. 1.5 g resting tension was applied and isometric contraction measured using a computerized Power Lab, Chart 5 data acquisition system (ADInstruments). Cumulative concentration‐response curves (CRC) were obtained for β‐phenylethylamine hydrochloride. Contractions were measured by subtracting baseline tension from plateau responses and expressed as a percentage of the contraction to KCl (60mM) added at the end. Responses were compared by Student's paired t‐test, P≤0.05 indicating significance. PEA showed concentration‐related contractions that were significantly greater at the maximum in the artery (1.53±0.31g, n=9) than the vein (0.55±0.18g, n=10). However, when plotted as % of the KCl maximum contraction, the maximum responses were not significantly different (vein 66.7±9.5%; artery 74.7±4.6% at 3×10−3M), indicating the overall greater contractility of this artery. PEA showed slowly developing contractions in both tissues which reached plateau effect after about 20 min. The reference α‐adrenoceptor agonist, phenylephrine, showed a much more rapid contraction, which was not sustained. In the saphenous vein, PEA (62.8±10.7%KCl) and phenylephrine (61.4±9.7%KCl, n=4) displayed the same maximum responses at 3×10−3M and 3×10−4M respectively, but phenylephrine was more potent. The α1‐adrenoceptor antagonist, prazosin (1μM) dissolved in 1 in 10 DMSO, blocked the responses to phenylephrine in the mammary artery but did not affect the contractions to PEA. Similarly, in the saphenous vein, prazosin (1μM) did not block the contractions to PEA. The DMSO vehicle for prazosin had no effect on PEA in mammary artery or saphenous vein. Thus, the indirect sympathomimetic and trace amine, PEA, has been shown to cause substantial vasoconstriction of human saphenous vein and mammary artery, which would explain its vasopressor actions in humans. This response however was not mediated via α1‐adrenoceptors, but was likely due to stimulation of TAARs.

Effect of Benidipine in Human Internal Mammary Artery and Clinical Implications

Graft spasm remains challenging in coronary artery bypass grafting (CABG). Calcium antagonists are commonly used in patients with coronary artery disease. This study investigated the inhibitory effect of third-generation dihydropyridine calcium channel antagonist benidipine on the vasoconstriction induced by various vasoconstrictors in the human internal mammary artery (IMA). Isolated human IMA rings (N= 65, taken from 37 patients undergoing CABG) were studied in a myograph in 2 ways: the relaxing effect of benidipine on vasoconstrictor-induced precontraction by KCl and U46619 and the depressing effect of benidipine at plasma concentrations on the contraction. Enzyme-linked immunosorbent assay (ELISA) was used to measure the change of the protein related to the L-type calcium channel. Benidipine caused more relaxation in KCl-contracted (86.7% ± 3.3%; n= 12) than in U46619-contracted (63.8% ± 5.3%; n= 8; p < 0.001) IMA rings. Pretreatment of IMA with plasma concentrations of benidipine (-6.92 log M) significantly depressed subsequent contraction by KCl (from 17.3 ± 2.7 mN to 7.4 ± 1.2 mN; n=6; p < 0.05) but did not significantly affect the contraction caused by U46619. Benidipine also caused a decrease of caveolin (CaV)1.2 protein content (0.55 ± 0.02 versus 0.63±0.02 mg/mL; p < 0.05). We conclude that in human IMA, the third-generation dihydropyridine calcium channel antagonist benidipine has a potent inhibitory effect on the vasoconstriction mediated by a variety of vasoconstrictors. Use of benidipine in patients undergoing CABG may provide vasorelaxant or antispastic effects in the grafts.

In vitro effects of sodium nitroprusside and leptin on norepinephrine-induced vasoconstriction in human internal mammary artery.

SummaryAimThe biological and pharmacological properties of vessels used in coronary artery bypass graft (CABG) surgery are as important as their mechanical properties. The aim of this study was to investigate the possible role of protein kinase C (PKC)-dependent mechanisms in leptin-induced relaxation in the human internal mammary artery (IMA).MethodsIMA rings, obtained from patients undergoing CABG surgery, were suspended in isolated tissue baths containing Krebs-Henseleit solution, which were continuously gassed with 95% O2 and 5% CO2 at 37°C.ResultsThe IMA rings were pre-contracted with increasing concentrations of norepinephrine (NE 10-9–10-4 mol/l) and the relaxation responses to sodium nitroprusside (SNP), a nitrosovasodilator, and leptin were studied in the presence and absence of a PKC inhibitor. Leptin (1 μM) caused a dose-dependent relaxation in NE pre-contracted IMA rings. Pre-treatment with a PKC inhibitor significantly attenuated this vasorelaxatory response to leptin in human isolated IMA.ConclusionIt was found that SNP and leptin caused significant relaxation of the NE pre-contracted human IMA rings, and PKC was probably the sub-cellular mediator for this effect. Our findings may have clinical or pharmacological importance as it could be hypothesised that obese subjects who have a left IMA bypass graft would have better myocardial perfusion.

Alendronate Decreases Contractile Responses by Affecting ATP-Sensitive Potassium Channels in Human Left Internal Mammary Artery Rings

Alendronate Decreases Contractile Responses by Affecting ATP-Sensitive Potassium Channels in Human Left Internal Mammary Artery Rings

Pharmacokinetic comparison of the vasorelaxant compound ferulic acid following the administration of Guanxin II to healthy volunteers and patients with angina pectoris

Coronary heart disease (CHD) is the leading cause of mortality worldwide. The Chinese medicinal formula Guanxin II has been shown to have a favorable effect in the attenuation of angina. The aim of this study was to compare the pharmacokinetics of ferulic acid (FA), which is a vasorelaxant compound present in Guanxin II, in healthy volunteers and patients with angina pectoris following the administration of Guanxin II. Ex vivo experiments were performed in order to investigate the vasorelaxant effect of FA on the human internal mammary artery (IMA) to provide evidence that it is a bioactive component of Guanxin II. Following the oral administration of Guanxin II, the FA levels in the serum were quantified by a simple and rapid high-performance liquid chromatography (HPLC) method. Treatment with FA (10−8−10−3 M) caused a concentration-dependent relaxation of endothelial IMA rings following precontraction with KCl. Statistically significant differences were identified between the pharmaco-kinetic parameters Cmax, t1/2α, t1/2β and t1/2Ka of the healthy volunteers and the patients with angina pectoris following the oral administration of Guanxin II. FA is a bioactive compound absorbed from Guanxin II that attenuates angina pectoris, a condition that may modify the pharmacokinetics of FA. Not only do the pharmacokinetic parameters direct the clinical use of Guanxin II, but they may also be useful for exploring the pathology of angina pectoris.

Comparative Effects of Preoperative Angiotensin-converting Enzyme In-hibitor, Statin and Beta-blocker Treatment on Human Internal Mammary Artery Reactivity in Patients with Coronary Artery Disease: A Pilot Study

We investigated the effect of angiotensin-converting enzyme (ACE)- inhibitor, statin, and beta-blocker usage before coronary bypass surgery (CABG) on vascular reactivity of the internal mammary artery (IMA). Patients, who underwent elective CABG were evaluated. Samples of IMA obtained from 22 patients were divided into 4 groups in respect of drugs used by patients before bypass surgery (control group, ACE inhibitor + statin group, ACE inhibitor + statin + beta-blocker group, and ACE inhibitor + beta-blocker group). The discarded, distal end section of IMA was carefully removed, and the vasoreactivity of IMA rings was evaluated in vitro using an organ chamber. Smooth muscle contractile function was tested on artery segments exposed to 10-80 mM KCl and norepinephrine. The endothelial function of IMA rings was assessed with acetylcholine (ACh) and bradykinin, while endothelium-independent vasorelaxation was evaluated by sodium nitroprusside (SNP). Both ACh and bradykinin caused concentration-dependent relaxation in endothelium-intact IMA rings. However, the maximal effect produced by endothelium-dependent agents in all treatment groups was more prominent when compared with the control group. There was no significant difference in the endothelium-dependent relaxation response of IMA between ACE inhibitor + statin, ACE inhibitor + beta-blocker and ACE inhibitor + statin + beta-blocker groups. The vasodilatory potency of SNP was similar in all groups. Similarly, contractile response to KCl or norepinephrine was not significantly different between groups. Use of ACE inhibitors and statins before bypass surgery may influence IMA vasoreactivity by improving endothelial control of vascular tone.

Pravastatin Improves Endothelial Function in Arteries Used in Coronary Bypass Grafting

Internal mammary artery (IMA) and radial artery (RA) are the 2 main arterial conduits used in coronary artery bypass grafting (CABG). The aim of this study was to analyze in vitro the vasoreactive properties in both vessels and to investigate the effects of pravastatin incubation on vascular function. IMA and RA rings obtained from patients undergoing CABG were studied in organ baths. We examined the contractile responses to phenylephrine and U46619 and the relaxation to acetylcholine (ACh) and sodium nitroprusside. In another series of experiments, the vascular reactivity and the superoxide anion production were studied after incubation with pravastatin. The effect of mevalonic acid on such responses was also assessed. Our results show that RA significantly evoked greater tension in response to vasoconstrictor agents and higher relaxation to ACh than IMA. In contrast, relaxation induced by sodium nitroprusside was not significantly different. Incubation with pravastatin reduced the contractile response to U46619 and improved the endothelium-dependent relaxation to ACh in both arteries. Whereas the effect of pravastatin on response to U46619 was completely abolished by coincubation with mevalonic acid, only a partial inhibition on ACh relaxation was observed. In conclusion, in vitro incubation with pravastatin enhanced endothelial function in IMA and RA. This suggests that postoperative (may include intraoperative) administration of statins could improve the endothelial function of arterial grafts in patients undergoing CABG.

Effect of Azelnidipine in Human Internal Mammary Artery and Clinical Implications

Graft spasm remains challenging in coronary artery bypass grafting (CABG) surgery. We investigated the inhibitory effect of a dihydropyridine calcium antagonist azelnidipine on the vasoconstriction mediated by potassium chloride (KCl) and U46619 in human internal mammary artery (IMA) from patients undergoing CABG. Isolated IMA rings (n = 68, taken from 28 patients) were studied in organ baths in two ways: the relaxing effect of azelnidipine on vasoconstrictor‐induced precontraction by KCl and U46619 and the depressing effect of azelnidipine on the contraction. Azelnidipine caused full relaxation in KCl‐contracted (96.5% ± 0.7%) and in U46619‐contracted (96.5% ± 1.4%) IMA rings (n = 8) with 28.8‐fold higher potency to KCl than to U46619 (EC50: −7.49 ± 0.21 vs −6.03 ± 0.11 log M, p &lt; 0.01). Pretreatment of IMA with plasma concentrations of azelnidipine (−6.1 log M) significantly depressed subsequent contraction to KCl (from 25.8 ± 2.2 mN to 16.0 ± 1.5 mN, p &lt; 0.05) and U46619 (from 30.6 ± 4.0 mN to 16.5 ± 2.2 mN, p &lt; 0.01). We conclude that in human IMA azelnidipine has a potent inhibitory effect on the vasoconstriction mediated by a variety of vasoconstrictors. Thus, use of azelnidipine in CABG patients is favored in treating and preventing graft spasm.Supported by NSF 81170148, 2010CB529500, 2009DFB30560, 09ZCZDSF04200, 10JCYBJC26400, 2012‐BH110004, 2011BHKZ001 &amp; 2011BHKY002, and CUHK4789/09, China.

Comparative Effects of Preoperative Angiotensin-converting Enzyme In-hibitor, Statin and Beta-blocker Treatment on Human Internal Mammary Artery Reactivity in Patients with Coronary Artery Disease: A Pilot Study

Purpose: We investigated the effect of angiotensin-converting enzyme (ACE)- inhibitor, statin, and beta-blocker usage before coronary bypass surgery (CABG) on vascular reactivity of the internal mammary artery (IMA). Methods: Patients, who underwent elective CABG were evaluated. Samples of IMA obtained from 22 patients were divided into 4 groups in respect of drugs used by patients before bypass surgery (control group, ACE inhibitor + statin group, ACE inhibitor + statin + beta-blocker group, and ACE inhibitor + beta-blocker group). The discarded, distal end section of IMA was carefully removed, and the vasoreactivity of IMA rings was evaluated in vitro using an organ chamber. Smooth muscle contractile function was tested on artery segments exposed to 10-80 mM KCl and norepinephrine. The endothelial function of IMA rings was assessed with acetylcholine (ACh) and bradykinin, while endothelium-independent vasorelaxation was evaluated by sodium nitroprusside (SNP). Results: Both ACh and bradykinin caused concentration-dependent relaxation in endothelium-intact IMA rings. However, the maximal effect produced by endothelium-dependent agents in all treatment groups was more prominent when compared with the control group. There was no significant difference in the endothelium-dependent relaxation response of IMA between ACE inhibitor + statin, ACE inhibitor + beta-blocker and ACE inhibitor + statin + beta-blocker groups. The vasodilatory potency of SNP was similar in all groups. Similarly, contractile response to KCl or norepinephrine was not significantly different between groups. Conclusion: Use of ACE inhibitors and statins before bypass surgery may influence IMA vasoreactivity by improving endothelial control of vascular tone.

Role of TRPC3 Channel in Human Internal Mammary Artery

Intracellular calcium regulation in endothelial cells depends on transient receptor potential channels (TRPs). Canonical TRPs (TRPCs) are now recognized as the most important Ca(2+)-permeable cation channels in vascular endothelium and TRPC3 channel is reported to play a role in vasodilation in animal vessels. However, little is known about the role of TRPCs in human arteries. We therefore tested the hypothesis that TRPCs play a role in human arteries. Cumulative concentration-relaxation curves to acetylcholine (-11 to -4.5 log M) were established in the human internal mammary artery (IMA) rings (n=42) taken from 28 patients undergoing coronary artery bypass grafting in precontraction induced by U46619 (-8 log M) in the absence or presence of SKF96365 (10 μmol/L) or Pyr3 (3μmol/L). Protein expressions of TRPC3 were determined by Western blot and immunohistochemistry staining. The maximal relaxation induced by acetylcholine was significantly attenuated by the nonspecific cation channels inhibitor, SKF96365 (48.2±3.7 vs. 66.0±0.9% in control, p <0.01) or the selective TRPC3 blocker, Pyr3 (58.4±2.3% vs. 67.7±1.1% in control, p <0.01). Protein expression of TRPC3 was detected in human IMA. TRPC3 exists and plays a role in the acetylcholine-induced endothelium-dependent relaxation in the human IMA. This study suggests that TRPC3 may be a potential new target in endothelial protection in patients with endothelial dysfunction such as in patients with coronary artery disease in order to improve the long-term patency of the grafting vessels.

Preservation of human artery function following prolonged cold storage with a new solution

Blood vessels are an important tissue for allogenic vessel replacement surgery, which is needed for example following infection of artificial grafts. For tissue banking, European legislation requires evidence of tissue sterility with assays performed over 1 week. Currently, used cold storage solutions do not protect vascular function longer than 2 days. This does not allow completion of microbiological testing. This discrepancy has almost completely stopped vessel banking in Europe. We compared the recently developed storage solution TiProtec (Dr F Köhler Chemie, Bensheim, Germany) with traditionally used histidine-tryptophan-ketoglutarate (HTK) solution, 0.9% NaCl, and phosphate-buffered saline (physiological saline solution [PSS]) solution for extended cold (4°C) storage up to 25 days. Isolated rings of human internal mammary artery were studied with respect to several parameters of vessel function, including vessel tone development, endothelium-dependent and endothelium-independent relaxation, and tissue reductive capacity. Vessels stored in NaCl or PSS for ≥10 hours failed to develop tone after rewarming. Mammary arteries stored in HTK for 4 hours at 4°C initially showed a well-preserved vessel function with respect to vessel tone development, as well as endothelial and smooth muscle dilatative function. However, following 4 days of cold storage, vessel tone development and dilatative responses were significantly impaired. In contrast, arteries stored in TiProtec showed full preservation of vessel tone as well as endothelial and smooth muscle function after 4 days of cold storage. Even after 10 days of cold storage, endothelium-dependent relaxation was approximately 50% of control, and smooth muscle function was fully preserved. Over 2 weeks, tissue reductive capacity was significantly better maintained after cold storage in TiProtec compared with vessels stored in NaCl. In contrast to traditional HTK, NaCl, or PSS storage, TiProtec solution offers an excellent potential for prolonged cold storage of human arteries, which may close the existing gap between legal requirements for tissue banking and current cold preservation methods.

Nitric Oxide Modulates Reactivity to Angiotensin II in Internal Mammary Arterial Grafts in Hytertensive Patients Without Associated Risk Factors

We investigated the effects of extraendothelial nitric oxide (NO) on angiotensin II (Ang II) reactivity in internal mammary artery (IMA) rings, as well as the impact of hypertension without associated risk factors in this response. Vascular reactivity, NO levels, and resting membrane potentials were determined in hypertensive (HT) and normotensive (NT) IMA rings. Only rings with endothelial dysfunction were included. Ang II produced a dose-dependent contraction that was higher in HT rings. Response to Ang II was potentiated by Nω-nitro L-arginine methyl ester (L-NAME) in NT but not in HT rings. The antioxidant agents tempol and diphenyleneiodonium (DPI) reverted the hyperreactivity to Ang II in HT rings. Extraendothelial NO was present in both NT and HT rings. However, NT rings showed higher values. L‐NAME and S-methyl-L-thiocitrulline inhibited NO release in all cases. L-arginine reverted this inhibition. Both tempol and DPI increased NO release in both NT and HT rings. The number of vascular smooth muscle cells (VSMC) and anti-α-actin positive areas were lower in HT than in NT rings, without variations in wall thickness or wall/lumen ratio. With regard to resting membrane potential, we found in HT rings that the depolarization induced by Ang II was abolished by tempol. These findings suggest that extraendothelial NO counterregulates Ang II contractility in IMA rings; however, its action could be altered in hypertensive situations even though the patients did not have associated risk factors. We suggest two mechanisms: increased oxidative stress and a decreased ability of nNOS in VSMC to produce NO.