Relative Contributions of 5-Hydroxytryptamine (5-HT) Receptor Subtypes in 5-HT-Induced Vasoconstriction of the Distended Human Saphenous Vein as a Coronary Artery Bypass Graft

Abstract

It is established that the segment of saphenous vein (SV) that is widely used as a conduit vessel in coronary artery bypass graft (CABG) surgery is distended with high pressure to check for leaks and to increase the patency before implantation into coronary arterial circulation. The aim of the present study was to elucidate the relative contributions of 5-hydroxytryptamine (5-HT) receptor subtypes responsible for 5-HT-induced vasoconstriction of the distended human SV. Whereas about half of the 5-HT-induced vasoconstriction still remained in the presence of supramaximum concentration of sarpogrelate or of SB224289 (5-HT_2A and 5-HT_1B receptor antagonists, respectively), simultaneous treatment with sarpogrelate and SB224289 almost completely inhibited the 5-HT-induced vasoconstriction. Immunopositive staining for 5-HT_2A and 5-HT_1B receptors was detected in smooth muscle cells of the distended human SV and there was no significant difference between the immunopositive areas of 5-HT_2A and 5-HT_1B receptors. These results demonstrate that 5-HT_2A and 5-HT_1B receptors similarly contribute to 5-HT-induced vasoconstriction in human distended SV. Thus, when the SV is used as a CABG conduit, a combination of 5-HT_2A and 5-HT_1B receptor antagonists would appear to be most useful to prevent 5-HT-induced spasm.