5-HT1-like receptor-mediated contraction in the human internal mammary artery

Arterial segments as microvascular interposition grafts in venous anastomosis in digital replantations

Introduction:

Microvascular anastomosis is a crucial procedure in replantation surgeries. Venous insufficiency is one of the most consistent cause of failure or re-exploration in these surgeries necessitating the use of venous grafts.

Materials and Methods:

We discuss our study of 9 such replantation surgeries executed in calendar year 2013-2014, including a double finger replantation done in the same patient having total amputation of 4 fingers of the same (right) hand, in which an arterial segment was used as a microvascular interposition graft for venous anastomosis. Out of these 9 surgeries, 3 were re-exploration procedures for venous compromise and 6 were successful primary replantations.

Results:

In all, 8 replants were successful and one failed due to arterial compromise.

Discussion:

In our experience and extensive review of the previously available literature, we would like to portray the advantages of arterial segments as microvascular grafts in replant surgeries. Specifically, in a crush amputation injury for which the use of a vascular interposition graft is being contemplated. If any other digit is also amputated and is unsuitable for replantation, it can act as a potential donor site to harvest the arterial segment. However, when dealing with single finger amputation, the surgeon must be confident about the single digital arterial anastomosis, before harvesting the second digital artery as a microvascular graft.

Conclusion:

In our study, we found the use of arterial grafts in microvascular anastomosis of veins advantageous, as arterial segments have better ability to resist spasm due to environmental changes, better pressure tolerance as compared to venous segments, and provide an appropriate calibre match and ease of harvest in the same operative field.

Arterial grafts: clinical classification and pharmacological management

In comparison with standard saphenous vein grafts, use of the internal mammary artery (IMA) as a coronary artery bypass graft has achieved superior long-term results. This is related to the differences in the biological characteristics between the venous and arterial grafts. However, even arterial grafts are not uniform in their biological characteristics. The variation in the perioperative behavior of the grafts and in their long-term patency may be related to different characteristics. These factors should be taken into account in the use of arterial grafts, some of which are subjected to more active pharmacological intervention during and after the operation to obtain satisfactory results. To better understand the biological behavior of the grafts, their common features and their differences, a clinical classification may be useful for a practicing surgeon. Based on experimental studies of their vasoreactivity combined with anatomical, physiological and embryological considerations, we have proposed a functional classification for arterial grafts that may be useful clinically. Our classification suggests that there are three types of arterial grafts: Type I-somatic arteries; Type II-splanchnic arteries; and Type III-limb arteries. Type I arteries have enhanced endothelial function and release more nitric oxide and other relaxing factors. Type II arteries, such as the gastro-epiploic artery, and Type III arteries, such as the radial artery (RA), have higher pharmacological reactivity to vasoconstrictors. This classification explains why the IMA has the best long-term patency. Because Type II and III arteries are prone to spasms due to higher contractility, they require more active pharmacological interventions. Furthermore, the harvesting technique of the conduits, including the saphenous vein and IMA, are described and discussed in this article. Prevention of spasms using two cocktails of medications (verapamil + nitroglycerin and nicardipine + nitroglycerin) during harvesting of the conduits is described. These solutions have been demonstrated to be clinically effective.

Dexmedetomidine Produces Dual α2-Adrenergic Agonist and α1-Adrenergic Antagonist Actions on Human Isolated Internal Mammary Artery

OBJECTIVE

To investigate the direct effects of dexmedetomidine (DEX) on isolated human internal mammary artery (IMA).

DESIGN

In vitro experimental study.

SETTING

Cardiovascular Pharmacology Laboratory, Department of Pharmacology, Gulhane School of Medicine, Ankara, Turkey.

PARTICIPANTS

IMA segments were obtained from 18 patients undergoing coronary artery bypass surgery.

INTERVENTIONS

The response in IMA was recorded isometrically by a force displacement transducer in isolated organ baths. DEX-induced contractions were tested in the presence of the alpha2-adrenoceptor antagonist yohimbine (10(-7) mol/L) and the alpha1-adrenoceptor antagonist prazosin (10(-8) M). The effect of DEX (10(-7), 10(-6), and 10(-5) mol/L) on phenylephrine (10(-9)-3 x 10(-4) mol/L)-induced contactions was also tested.

MEASUREMENT AND MAIN RESULTS

DEX (10(-9) mol/L-3 x 10(-5) mol/L) caused contraction in IMA segments. The contraction at lower concentrations of DEX (10(-9) mol/L-3 x 10(-7) mol/L) was attenuated by yohimbine (10(-7) mol/L), whereas prazosin (10(-8) mol/L) attenuated the contractions at higher concentrations of DEX (10(-6) mol/L-3 x 10(-5) mol/L). Incubation of IMA segments with high concentrations of DEX (10(-6) mol/L and 10(-5) mol/L) caused an inhibition of phenylephrine (10(-9) mol/L-3 x 10(-4) mol/L)-induced contraction.

CONCLUSION

These data suggest that DEX causes contraction by activating alpha2-adrenoceptors at lower concentrations, but it may also activate alpha1-adrenoceptors at higher concentrations in IMA. The action of DEX on phenylephrine-induced contraction may be related to an alpha1-adrenoceptor antagonistic effect produced via partial alpha1-adrenoceptor agonistic action.

Effects of current and prospective antimigraine drugs on the porcine isolated meningeal artery

Vasoconstriction to agonists at serotonin (5-hydroxytryptamine; 5-HT) receptors and alpha-adrenoceptors, as well as vasodilatation induced by alpha-CGRP, have been well described in the porcine carotid circulation in vivo. The present study sets out to investigate the effects of current and prospective antimigraine drugs on porcine meningeal artery segments in vitro. Sumatriptan, ergotamine, dihydroergotamine, isometheptene and clonidine failed to contract the meningeal artery, but 5-HT, noradrenaline and phenylephrine induced concentration-dependent contractions. The contractions to 5-HT were competitively antagonized by the 5-HT(2A) receptor antagonist ketanserin, whilst those to noradrenaline were antagonized by alpha(1)-(prazosin), alpha(2)-(rauwolscine and yohimbine) and alpha(2C/2B)-(OPC-28326) adrenoceptor antagonists. Whilst dobutamine and salbutamol were ineffective, alpha-CGRP produced concentration-dependent relaxations that were antagonized by the CGRP(1) receptor antagonist olcegepant. In agreement with their lack of contractile effect, sumatriptan and ergotamine failed to influence forskolin-stimulated cyclic AMP accumulation in the porcine meningeal artery; in contrast, both compounds decreased forskolin-stimulated cyclic AMP accumulation in the human isolated saphenous vein, where they induced contractions. Finally, using RT-PCR, we could demonstrate the presence of mRNAs encoding for several 5-HT receptors (5-HT(1B), 5-HT(1D), 5-HT(1F), 5-HT(2A) and 5-HT(7)) and adrenoceptors (alpha(1A), alpha(1B), alpha(1D), alpha(2A), alpha(2B), alpha(2C), beta(1) and beta(2)), as well as that for the calcitonin receptor like receptor, a component of the CGRP(1) receptor. These results suggest that: (i) the porcine meningeal artery may not be involved in the vasoconstriction of the carotid vascular bed elicited by antimigraine drugs in anaesthetized pigs, and (ii) the mismatch between the presence of receptor mRNA and the lack of response to sumatriptan, dobutamine and salbutamol implies that mRNAs for the 5-HT(1B) receptor and beta(1)- and beta(2)-adrenoceptors are probably unstable, or that their density is too low for being translated as receptor protein in sufficient quantities.

5-Hydroxytryptamine receptors in the human cardiovascular system

The human cardiovascular system is exposed to plasma 5-hydroxytryptamine (5-HT, serotonin), usually released from platelets. 5-HT can produce harmful acute and chronic effects. The acute cardiac effects of 5-HT consist of tachycardia (preceded on occasion by a brief reflex bradycardia), increased atrial contractility and production of atrial arrhythmias. Acute inotropic, lusitropic and arrhythmic effects of 5-HT on human ventricle become conspicuous after inhibition of phosphodiesterase (PDE) activity. Human cardiostimulation is mediated through 5-HT4 receptors. Atrial and ventricular PDE3 activity exerts a protective role against potentially harmful cardiostimulation. Chronic exposure to high levels of 5-HT (from metastatic carcinoid tumours), the anorectic drug fenfluramine and its metabolites, as well as the ecstasy drug 3,4-methylenedioxymethamphetamine (MDMA) and its metabolite 3,4-methylenedioxyamphetamine (MDA) are associated with proliferative disease and thickening of cardiac valves, mediated through 5-HT2B receptors. 5-HT2B receptors have an obligatory physiological role in murine cardiac embryology but whether this happens in humans requires research. Congenital heart block (CHB) is, on occasion, associated with autoantibodies against 5-HT4 receptors. Acute vascular constriction by 5-HT is usually shared by 5-HT1B and 5-HT2A receptors, except in intracranial arteries which constrict only through 5-HT1B receptors. Both 5-HT1B and 5-HT2A receptors can mediate coronary artery spasm but only 5-HT1B receptors appear involved in coronary spasm of patients treated with triptans or with Prinzmetal angina. 5-HT2A receptors constrict the portal venous system including oesophageal collaterals in cirrhosis. Chronic exposure to 5-HT can contribute to pulmonary hypertension through activation of constrictor 5-HT1B receptors and proliferative 5-HT2B receptors, and possibly through direct intracellular effects.

Potassium channel-related relaxation by levosimendan in the human internal mammary artery

BACKGROUND

Levosimendan is a potent inotropic and vasodilator drug used in the treatment of decompensated heart failure. There is no study on in vitro effects of levosimendan in human isolated arteries.

METHODS

We investigated the effect of levosimendan on contractile tone of human isolated internal mammary artery (IMA). The responses in IMA were recorded isometrically by a force-displacement transducer in isolated organ baths. Levosimendan was added to organ baths either at rest or after precontraction with phenylephrine (1 micromol/L). Levosimendan-induced relaxations were tested in the presence of cyclooxygenase inhibitor indomethacin (10 micromol/L), nitric oxide synthase inhibitor N122-nitro-L-arginine methyl ester (100 micromol/L), large-conductance calcium-activated potassium-channel inhibitor tetraethylammonium (1 mmol/L), adenosine triphosphate-sensitive potassium-channel inhibitor glibenclamide (10 micromol/L), and voltage-sensitive potassium-channel inhibitor 4-aminopyridine (1 mmol/L).

RESULTS

Levosimendan (10 nmol/L to 3 micromol/L) produced potent relaxation in human IMA (maximal effect, 75.3% +/- 4.9% of phenylephrine maximum contraction, 6.8 +/- 0.1, n = 15; -log10 of 50% effective concentration). Vehicle had no significant relaxant effect. The relaxation to levosimendan is not affected by either potassium-channel inhibitors (tetraethylammonium and 4-aminopyridine) or cyclooxygenase and nitric oxide synthase inhibitors. Glibenclamide (10 micromol/L) inhibited levosimendan-induced relaxation significantly (p < 0.01).

CONCLUSIONS

Levosimendan effectively and directly decreases the tone of IMA. The mechanism of levosimendan-induced relaxation in IMA appears in part to be adenosine triphosphate-sensitive potassium-channel opening action. Levosimendan may be a cardiovascular protective agent by its relaxing action on the major arterial graft, IMA.

Triptans induce vasoconstriction of human arteries and veins from the thoracic wall

A common side effect of migraine treatment with triptans is chest symptoms. The origin of these symptoms is not known. The aim of the present study was to examine the vasocontractile effect of triptans in human arteries and veins from the thoracic wall and in coronary artery bypass grafts. In vitro pharmacology experiments showed that the 5-hydroxytryptamine (5-HT) type 1B and 1D receptor agonists, eletriptan, naratriptan, rizatriptan, sumatriptan, and zolmitriptan, induced vasoconstriction in the thoracic blood vessels from 38% to 57% of the patients. 5-carboxamidotryptamine (5-CT) and sumatriptan elicited a vasoconstriction that was antagonized by the 5-HT1B receptor antagonist SB224289, whereas the 5-HT1D receptor antagonist BRL115572 had no effect. 5-HT induced a contraction that was inhibited by the 5-HT2A receptor antagonist ketanserin. 5-HT2A, 5-HT1B, and 5-HT1D receptor mRNA levels were detected by real-time PCR in all blood vessels studied. In conclusion, triptans induce vasoconstriction in arteries and veins from the thoracic wall, most likely by activation of 5-HT1B receptors. This response could be observed in only 38% to 57% of the patients, which may provide an explanation for why a similar number of patients experience chest symptoms as a side effect of migraine treatment with triptans.

Testosterone Relaxes Human Internal Mammary Artery In Vitro

Preliminary clinical studies of testosterone therapy in male patients with coronary artery disease raised promising results. However, there is no study on in vitro effects of testosterone in human isolated arteries. We investigated the effect of testosterone on contractile tone of human isolated internal mammary artery. The responses in human internal mammary artery (IMA) were recorded isometrically by a force-displacement transducer in isolated organ baths. Testosterone (10 nM to 100 microM) was added cumulatively to organ baths either at rest or after precontraction with KCl (68 mM) and PGF2alpha (10 microM). Testosterone-induced relaxations were tested in the presence of cyclooxygenase inhibitor indomethacin (10 microM), nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME, 1 microM), nonselective large-conductance Ca2+-activated and voltage-sensitive K+ channel inhibitor tetraethylammonium (TEA, 1 mM), ATP-sensitive K+ channel inhibitor glibenclamide (GLI, 100 microM), and voltage-sensitive K+ channel inhibitor 4-aminopyridine (4-AP, 1 mM). Testosterone produced relaxation in human IMA (Emax 33% and 41% of KCl- and PGF2alpha-induced contraction, respectively). Vehicle had no significant relaxant effect. Except for TEA, the relaxation at low concentrations is not affected by either K+ channel inhibitors (GLI and 4-AP) or L-NAME and indomethacin. We report for the first time that supraphysiological concentrations of testosterone induce relaxation in IMA. This response may occur in part via large-conductance Ca2+-activated K+ channel-opening action.

The Relationship Between Risk Factors and Testosterone-Induced Relaxations in Human Internal Mammary Artery

In human internal mammary artery (IMA), testosterone induces vasodilation that shows marked variability among patients. We aimed to investigate the relationship of this variability with cardiovascular risk factors. Cumulative relaxations to testosterone after precontraction with KCl were examined in IMA segments from patients with identified cardiovascular risk factors such as hypercholesterolemia, diabetes, hypertension, smoking, age, gender, body mass index (BMI), and number of occluded vessels. Testosterone responses were significantly diminished in subjects with 3 compared with 1 risk factor. Hypercholesterolemia independently influenced testosterone responses by significantly decreasing its maximum, and smoking significantly decreased the sensitivity to testosterone. Thus, the variability observed in testosterone-induced vascular relaxations may in part be related to differences in risk factors present among the individuals studied.

Pharmacologic characterization of contractile serotonergic receptors in human isolated mesenteric artery

The 5-hydroxytryptamine (5-HT) receptors mediating contraction in human isolated mesenteric arteries were characterized. Endothelium-denuded human isolated mesenteric arteries were used. 5-HT induced concentration-dependent contractions in mesenteric arteries (Emax, 127.37 +/- 7.61% of 80 mM KCl maximal contraction; pD2, 6.73 +/- 0.09 [-logEC50]). Sumatriptan, a selective 5-HT1B/1D receptor agonist, induced concentration-dependent contractions in some of the arteries (Emax, 61.82 +/- 10.04%; pD2, 6.56 +/- 0.21, n = 9) but not in the others (Emax < 5%, n = 13), suggesting that functional 5-HT1B/1D receptors exist in some but not in all mesenteric arteries. GR127935 (a selective 5-HT1B/1D receptor antagonist, 3 nM) inhibited sumatriptan-induced contractions in arteries in which sumatriptan responses were strong in an insurmountable manner. GR127935 (10 nM) also inhibited 5-HT responses and shifted the concentration-response curve of 5-HT to the right significantly (p < 0.05; pD2s were 6.54 +/- 0.18 and 5.93 +/- 0.11 in the presence of vehicle and GR127935, respectively). Ketanserin (0.01-1 microM) competitively antagonized 5-HT responses in human mesenteric arteries: pA2 value was 8.40 +/- 0.25 (slope of Schild regression, 1.43 +/- 0.18; r2, 0.98). Tropisetron (5-HT3 receptor antagonist) and prazosin (alpha1-adrenoceptor antagonist) did not affect the contractions induced by 5-HT. These results suggest that 5-HT2A and 5-HT1B/1D receptors, but not 5-HT3 and alpha1-adrenoceptors, are involved in the 5-HT-induced contractions in human isolated mesenteric arteries. Sumatriptan-induced and 5-HT1B/1D receptor-mediated responses vary greatly among patients.

Arterialization in coronary artery surgery in Japan and Hong Kong

In the 35 years of coronary artery bypass grafting, several kinds of conduits have been utilized and assessed. It is clear now that the saphenous vein graft deteriorated with time mainly due to atherosclerosis in the graft called "vein graft disease." The internal thoracic artery graft, on the contrary, stays patent very well in the long-term period and this evidence directly related to the superior later outcome in terms of longevity and postoperative cardiac events. To extend the use of arterial conduits for myocardial revascularization, several autologous arteries have been investigated and utilized clinically. With proper use of these new arterial conduits in addition to internal thoracic artery, coronary artery bypass grafting with multi-arterial grafts can be performed safely, and better long term result can be expected.

Smooth muscle and endothelial function of arterial grafts for coronary artery bypass surgery

1. Various small/mid-sized conductance arteries have been used for coronary artery bypass grafting as arterial grafts, but unanimous opinion to the best use of these grafts has not been formed. 2. Arterial grafts are not uniform in their biological characteristics. 3. The differences among the arteries may involve the contractility of the vessel. Based on studies of the contractility of arterial grafts, a clinical classification was formed to describe the tendency of vasospasm in the arterial grafts. 4. The differences among arterial grafts also involve endothelial function. This refers to both nitric oxide release from the endothelium, as well as endothelium-derived hyperpolarizing factor-mediated hyperpolarization and relaxation. 5. The difference in the peri-operative behaviour of the grafts and in their long-term patency may be related to different characteristics. These should be taken into account in the use of arterial grafts, some of which are subject to more active pharmacological intervention during and after operation to obtain satisfactory results. The clinical choice of grafts must be based on the general condition of the patient, the biological characteristics of the graft, the anatomy of the coronary artery, the match between the coronary artery and the graft and the technical considerations, including antispastic management.

Effects of SL 65.0472, a novel 5-HT receptor antagonist, on 5-HT receptor mediated vascular contraction

5-hydroxytryptamine (5-HT) contracts vascular smooth muscle and pharmacological and molecular biological data suggest that these effects are mediated primarily by stimulation of 5-HT(1B) and 5-HT(2A) receptor subtypes. We have studied the properties of 7-fluoro-2-oxo-4-[2-[4-(thieno[3,2-c] pyridin-4-yl) piperazin-1-yl] ethyl]-1,2-dihydroquinoline-1-acetamide (SL 65.0472 ), a novel 5-HT receptor antagonist, in isolated vascular preparations contracted by 5-HT or sumatriptan. In canine isolated saphenous vein strips (putatively 5-HT(1B)-mediated contraction), SL 65.0472 antagonised sumatriptan-induced contractions in a competitive manner (pA(2) 8. 17+/-0.36). 5-HT contracts rabbit aorta by stimulation of 5-HT(2A) receptors. SL 65.0472 displaced the 5-HT concentration response curve in rabbit aorta rightwards with a significant reduction in maximum. The apparent pK(B) value was 8.58+/-0.18. 5-HT-induced contractions of human coronary arteries are mediated by a mixed population of 5-HT(1B) and 5-HT(2A) receptors. SL 65.0472 produced rightward parallel shifts of the 5-HT concentration response curves in all tissues studied (pA(2) 8.8+/-0.14, n=7). In conclusion, SL 65. 0472 is a potent antagonist of vascular smooth muscle contraction in vitro mediated by 5-HT receptor stimulation.

Functional characterization and m-RNA expression of 5-HT receptors mediating contraction in human umbilical artery

5-HT1-like and 5-HT2 receptors have both been described to mediate contractions to 5-HT in the human umbilical artery (HUA). However, the nature of the 5-HT receptor subtypes is unknown. 2 In isometric force studies with ring preparations of HUA alpha-methyl-5-hydroxytryptamine (alpha-Me-5-HT) and 5-hydroxytryptamine (5-HT) contracted HUA with pED50 values of 8.04 and 7.74, respectively. In the presence of a subthreshold concentration of another vasoconstrictor sumatriptan and 5-nonyloxytryptamine elicited concentration-dependent contractions with pEC50 values of 7.21 and 7.67, respectively. In the presence of the selective 5-HT1B/D receptor antagonist GR127935, contractile responses elicited by sumatriptan and 5-nonyloxytryptamine were competitively antagonized (pKB 9.01 and 9.02, respectively). In the experiments with 5-HT, GR127935 appeared to be non-competitive with shallow Schild plot slopes. The data were fitted with two linear regression lines and the calculated pKB of the high affinity component (8.90) was comparable to that expected for GR127935 at the 5-HT1B/1D receptor. Several 5-HT2 selective receptor antagonists (spiperone, cyproheptadine, pirenperone) competitively inhibited responses to 5-HT. The selective 5-HT2A antagonist ketanserin against sumatriptan and 5-nonyloxytryptamine behaved as a weak antagonist while against 5-HT demonstrated a competitive antagonism (pKB 8.56). Using specific primers for human 5-HT1B, 5-HT1D and 5-HT2A receptor genes, the reverse transcriptase-polymerase chain reaction revealed mRNA expression of 5-HT1B and 5-HT2A receptors in the HUA. The results suggest that the HUA has a functional population of 5-HT1B and 5-HT2A receptor subtypes which are involved in the contractile response to 5-HT. Contractions mediated by 5-HT1B receptors can be 'uncovered' by exposure to other vasoactive agents.

Arterial grafts for coronary artery bypass grafting: biological characteristics, functional classification, and clinical choice

Various arterial grafts have been used for coronary artery bypass grafting, but a unanimous opinion on how to best use these grafts has not been formed. Arterial grafts are not uniform in their biological characteristics. Differences between the perioperative behavior of the grafts and their long-term patency may be related to different characteristics. These characteristics should be taken into account in the use of arterial grafts, some of which are subject to more active pharmacologic intervention during and after operation to obtain satisfactory results. Clinical choice of grafts must be based on the general condition of the patient, the biological characteristics of the graft, the anatomy of the coronary artery, the match between the coronary artery and the graft, and technical considerations, including antispastic management.

Serotonin and vasoconstrictor synergism

Contractile synergism between serotonin (5-hydroxytryptamine, 5-HT) and other vasoconstrictor substances has been observed in a number of peripheral and cerebrovascular blood vessels. This phenomenon may play an important role in certain pathological states such as hypertension, peripheral vascular disease, and coronary spasm. In the present review, we summarize studies on the synergism between serotonin and other vasoconstrictor agents and focus on a recently described type of vasoconstrictor synergism in which precontraction with a non-5-HT receptor agonist yields an enhanced contractile response to serotonin which is mediated by previously inactive or "silent" 5-HT receptor subtypes.

Hypertension increases the contractions to sumatriptan in the human internal mammary artery

BACKGROUND

The internal mammary artery is the graft of choice for myocardial revascularization. The tendency to spasm increases toward the distal end of the internal mammary artery, which is the portion generally used for anastomosis. The distal internal mammary artery is more pharmacologically responsive to 5-hydroxytryptamine and several other vasoconstrictor agents than its midsection.

METHODS

We examined the effects of 5-hydroxytryptamine and a 5-hydroxytryptamine1-like receptor agonist sumatriptan on internal mammary artery segments (length, 3-4 mm) obtained from patients undergoing coronary artery bypass grafting. To unmask a 5-hydroxytryptamine1-like receptor-mediated contractile response, threshold concentrations of potassium chloride were used.

RESULTS

5-Hydroxytryptamine induced concentration-dependent contractions in all, quiescent and potassium chloride precontracted, preparations. Sumatriptan induced marked contraction in some of the quiescent internal mammary artery rings, whereas it elicited marked and concentration-dependent contractions in all of the preparations given a moderate tone by a threshold concentration of potassium chloride. The sensitivity to sumatriptan was higher in potassium chloride-precontracted distal arteries than it was for the quiescent distal segments. Additionally, the sensitivity to and the efficacy of sumatriptan were much more markedly potentiated by precontraction in the preparations taken from hypertensive patients.

CONCLUSIONS

The more marked potentiation of the responses in arteries from hypertensive patients may be one of the factors influencing the patency rates.