Endothelium-denuded Saphenous Vein Research Articles

Diabetes Mellitus Induces Hyperreactivity of 5-Hydroxytryptamine (5-HT)-Induced Constriction in Human Internal Thoracic Artery and Is Associated with Increase in the Membrane Protein Level of 5-HT<sub>2A</sub> Receptor

Studies indicate that 5-hydroxytryptamine (5-HT) released from activated platelets in coronary artery bypass grafting (CABG) induces 5-HT2A receptor-mediated graft spasm. We previously reported that 5-HT-induced constriction of human endothelium-denuded saphenous vein (SV) was significantly augmented in patients with diabetes mellitus (DM) than in patients without DM (non-DM), without changes in the levels of the membrane-bound 5-HT2A receptor of their smooth muscle cells. Although the internal thoracic artery (ITA) is the key graft conduit for CABG, the effect of DM on the ITA graft spasm is still unclear. Therefore, in this study, we investigated the effect of DM on 5-HT-induced vasoconstriction and the level of membrane-bound 5-HT2A receptor in ITA grafts. 5-HT-induced constriction of the isolated human endothelial-denuded ITA was significantly higher in patients with DM than in patients without DM. In addition, the level of the 5-HT2A receptor in the membrane fraction of human ITA smooth muscle cells was significantly higher in patients with DM than in those without DM. These results demonstrate that DM is a risk factor for CABG in both venous and arterial conduits, and that it differentially affects the level of the membrane-bound 5-HT2A receptor in the venous and arterial smooth muscle cells.

Angiotensin II, as well as 5-hydroxytriptamine, is a potent vasospasm inducer of saphenous vein graft for coronary artery bypass grafting in patients with diabetes mellitus

Diabetes mellitus (DM) is an important risk factor for adverse outcomes of coronary artery bypass grafting. The bypass grafts harvested from patients with DM tend to go into spasm after their implantation into the coronary circulation. To clarify the contribution of 5-hydroxytriptamine (5-HT) and angiotensin II (AngII) in the bypass graft spasm, we examined the contractile reactivity to 5-HT or AngII of isolated human endothelium-denuded saphenous vein (SV) harvested from DM and non-DM patients. The 5-HT-induced constriction of the SV was significantly augmented in the DM group than in the non-DM group, which is similar to our previous report. AngII-induced constriction of the SV was also significantly augmented in the DM group than the non-DM group. Especially in the non-DM group, the AngII-induced maximal vasoconstriction was markedly lower than the 5-HT-induced one. Meanwhile, the increasing rates of AngII-induced vasoconstriction in the DM group to the non-DM group were significantly greater than those of 5-HT-induced vasoconstriction. These results indicate that 5-HT is a potent inducer of SV graft spasm in both DM and non-DM patients, while AngII is a potent inducer of SV graft spasm only in patients with DM. Furthermore, the protein level of AngII AT1 receptor (AT1R), but not the protein level of 5-HT2A receptor, in the membrane fraction of the SV smooth muscle cells of DM patients was significantly increased as compared with that of the non-DM patients. These results suggest that the mechanism for hyperreactivity to AngII in the SV from DM patients is due to, at least in part, the increase in the amount of AT1R on membrane of the SV smooth muscle cells.

Insulin Induces Internalization of the Plasma Membrane 5-Hydroxytryptamine2A (5-HT2A) Receptor in the Isolated Human Endothelium-Denuded Saphenous Vein via the Phosphatidylinositol 3-Kinase Pathway

The aim of this study was to investigate the relaxant effect of insulin on the 5-hydroxytryptamine (5-HT)-induced constriction of the human endothelium-denuded saphenous vein (SV) and its signal transduction pathway. During the 5-HT-induced sustained constriction of vessels, insulin induced vasorelaxation in a concentration-dependent manner. This insulin-induced vasorelaxation was partially attenuated by L-NAME, a nitric oxide synthase (NOS) inhibitor, and was abolished by wortmannin, a phosphatidylinositol 3-kinase (PI3-K) inhibitor. Insulin increased the Ser473 phosphorylation of Akt. Endothelial NOS and inducible NOS protein expressions were observed in SV smooth muscle when insulin induced relaxation of SV vessels preconstricted with 5-HT. Although insulin did not affect the total protein level of 5-HT2A receptors, it decreased the particulate protein level and reciprocally increased the soluble protein level of 5-HT2A receptors in a concentration-dependent manner. These results demonstrate that insulin can induce the internalization of 5-HT2A receptors from the plasma membrane to the cytoplasm. The insulin-induced internalization of 5-HT2A receptors was abolished by wortmannin but was not affected by L-NAME. These results suggest that the relaxant effect of insulin on 5-HT-induced vasoconstriction is mediated in part by the internalization of plasma membrane 5-HT2A receptors and the production of nitric oxide via the PI3-K/Akt pathway.

BAS/BSCR37 Discovery and characterisation of novel peptide agonists and the first antagonist for the cardiovascular peptides, the apelins

The recently discovered apelin family of peptides mediate their actions by a single G-protein coupled receptor, APJ. We have previously shown that apelins have three major actions in the human...

Pyr 1 ]Apelin-13 Identified as the Predominant Apelin Isoform in the Human Heart

Apelin receptors, present on vascular smooth muscle cells, endothelium, and cardiomyocytes, are activated by the family of apelin peptides to elicit cardiovascular effects in experimental animals, but functional activity in humans has not been studied in detail. We detected low levels of apelin immunoreactivity in plasma of volunteers consistent with an autocrine/paracrine action and detected apelin immunoreactivity in the supernatant from human cultured endothelial cells. We found that [Pyr(1)]apelin-13 was the predominant isoform in cardiac tissue from patients with coronary artery disease. We tested the hypothesis that apelins have vascular and cardiac actions in human tissues in vitro and compared responses to [Pyr(1)]apelin-13, apelin-13, and apelin-36. In endothelium-intact mammary artery, all 3 of the apelins induced concentration-dependent vasodilatation with comparable potency (EC(50): 0.6 to 1.6 nM; maximum response: 40% to 50%). Vasodilatation was abolished after endothelial removal or preincubation with indomethacin but was unaffected by preincubation with N(G)-nitro-L-arginine methyl ester, indicating involvement of prostanoids but not NO in dilatation by apelins in this patient group. Apelins were potent constrictors of endothelium-denuded saphenous vein (EC(50): 0.6 to 1.6 nM; maximum response: 17% to 26%) and mammary artery ([Pyr(1)]apelin-13; EC(50): 0.2 nM; maximum response: 29%). In paced atrial strips, all 3 of the peptides increased the force of contraction with subnanomolar potencies (EC(50): 40 to 125 pM). For the first time, we demonstrate that the 3 principal forms of apelin have comparable potency and efficacy in human cardiovascular tissues. Apelins are potent endothelium-dependent vasodilators acting via a prostanoid-dependent mechanism; however, removal of the endothelium revealed direct vasoconstrictor actions in both the artery and vein. Furthermore, in human cardiac tissue, the apelin peptides are among the most potent endogenous positive inotropic agents yet reported.

Interaction of 5-methyl-urapidil with α1-adrenoceptors in canine blood vessels: impact of pacing-induced heart failure

This study examines whether the alpha 1-adrenoceptors in canine endothelium-denuded dorsal pedal artery and endothelium-denuded saphenous vein can be differentiated by 5-methyl-urapidil before (non-paced) and at end-stage heart failure induced by rapid ventricular pacing. Noradrenaline and phenylephrine produced concentration-dependent contractions of the dorsal pedal artery and the saphenous vein which were enhanced at end-stage heart failure. In non-paced animals, 5-methyl-urapidil was shown to be insurmountable against noradrenaline with the artery being more sensitive compared to the vein. At end-stage heart failure, 5-methyl-urapidil was a competitive antagonist against noradrenaline in both the artery and the vein with pA2 values of 8.1 (7.9-8.4) and 8.6 (8.2-9.1), respectively. A different antagonist profile was seen against phenylephrine. Similar to noradrenaline, insurmountable antagonism was observed in the artery and the vein before the development of heart failure. In contrast to noradrenaline, at end-stage heart failure, no antagonism was seen with the concentrations of 5-methyl-urapidil tested against phenylephrine. These results suggest that the mechanisms mediating contractions in the dorsal pedal artery and saphenous vein to noradrenaline and phenylephrine are heterogeneous and dependent on the heart failure state.

Evidence for 5-HT1D beta but not 5-HT1D alpha receptor subtype expression in canine large coronary arteries and saphenous vein.

5-Hydroxytryptamine1D (5-HT1D) receptors are believed to play a major role in the vasoconstriction of vascular smooth muscle in human coronary arteries. However, unequivocal evidence as to which subtype of this receptor (5-HT1D alpha or 5-HT1D beta) is involved in these vasoconstrictory effects is lacking. The aim of this study was to identify in the dog the 5-HT1D receptor subtype encoding mRNAs expressed in several large coronary arteries and in the saphenous vein. Degenerate oligonucleotide primers that selectively recognized only mammalian 5-HT1D alpha and 5-HT1D beta receptor sequences were used in RT-PCR experiments to study 5-HT1D receptor subtype expression in endothelium-denuded saphenous vein and large coronary arteries from beagle and alsatian dogs. Resulting PCR products were analysed and identified by Southern blots and sequencing. An identical PCR product whose sequence closely resembles that of the human 5-HT1D beta receptor (98% amino acid identity) was obtained from reverse-transcribed RNA isolated from either saphenous vein or coronary arteries, irrespective of dog race. Absence of 5-HT1D alpha expression was confirmed by Southern blot analysis. Control experiments using canine genomic DNA as template illustrated, nonetheless, that the primers chosen could amplify both 5-HT1D alpha and 5-HT1D beta sequences. Using RT-PCR, we isolated from dog vascular smooth muscle a cDNA fragment whose nucleotide sequence would encode a previously-unreported canine homologue of the 5-HT1D beta receptor. We illustrated that this subtype is the only 5-HT1D receptor subtype expressed in dog saphenous vein and large coronary arteries. The implications of these findings are discussed in light of results from functional studies of 5-HT1-like receptor-mediated effects in these canine blood vessels.

Characterization of endothelin receptors mediating contraction and relaxation in rabbit saphenous artery and vein.

The endothelin receptors in rabbit isolated rings of saphenous artery and saphenous vein have been characterized using endothelin-1, endothelin-2, endothelin-3, sarafotoxin S6c, and BQ123. Although artery rings were more sensitive than those from vein to the contractile action of phenylephrine, endothelin-1 was about three times more potent as a contractile agonist on vein than on artery. In rings precontracted with phenylephrine, carbachol was 10 times more potent in vein than in artery rings to induce endothelium-dependent relaxation. However, in rings precontracted to a similar tone by endothelin-1, the relaxation elicited by carbachol was reduced in the vein but remained unchanged in the artery. In endothelium-denuded saphenous artery, endothelin-1 and endothelin-2 elicited contraction with equal potency, whereas endothelin-3 and sarafotoxin S6c were weak agonists. In saphenous vein, the rank order of sensitivity was sarafotoxin S6c > endothelin-2 > or = endothelin-1 = endothelin-3, whereas sarafotoxin S6c and, to a lesser extent, endothelin-3 act as partial agonists. The ETA receptor antagonist BQ123 shifted, to the right, the concentration-response curves of endothelin-1 on endothelium-denuded saphenous artery (pA2 = 7.25). In the endothelium-denuded saphenous vein, 10 microM BQ123 shifted to the right only the response to high concentrations of endothelin-1. In vein but not in artery, endothelin-1 and sarafotoxin S6c induced an endothelium-dependent relaxation, which was increased, in the case of endothelin-1, in the presence of BQ123.2+.