Cable D G, Caccitolo J A, Pearson P J, O'Brien T, Mullany C J, Daly R C, Orszulak T A, Schaff H V
Division of Thoracic and Cardiovascular Surgery, Mayo Clinic, Rochester, MN 55905, USA.
Circulation. 1998 Nov 10;98(19 Suppl):II15-21; discussion II21-2.
There has been renewed interest in radial artery (RA) conduits for coronary artery bypass because of the relative resistance of arterial grafts to atherosclerosis compared with autogenous vein grafts. Although improved drug therapy for arterial spasm is now available, vasospasm still occurs in at least 5% to 10% of RA grafts. We systematically evaluated the effectiveness of calcium channel blockers and organic nitrates for inhibition or reversal of RA contraction in vitro. Additionally, we investigated the efficacy of novel gene therapy with endothelial nitric oxide synthase (eNOS) to inhibit RA contractions.
Segments of RA from 28 patients undergoing coronary artery bypass grafting were mounted in organ chambers. In control experiments, KCl (5 to 50 mmol/L) produced dose-dependent increases in tension (maximum tension, 14.3 +/- 3.0 g, n = 7). Addition of diltiazem or verapamil had no significant effect on KCl contraction (128 +/- 36% and 88 +/- 24% control, respectively); however, nifedipine markedly inhibited KCl contraction (27 +/- 4% control, P = 0.005). Norepinephrine (NE, 10(-9) to 10(-4) M) produced dose-dependent increases in tension (maximum tension, 15.7 +/- 2.7 g in control rings, n = 8). Diltiazem and verapamil pretreatment had no significant effect on NE contraction (103 +/- 14% and 90 +/- 14% control, respectively); nifedipine significantly inhibited NE contraction (70 +/- 11% control, P = 0.02). Isosorbide dinitrate and nitroglycerin markedly inhibited KCl contractions (47 +/- 9% and 30 +/- 8% of controls, n = 6) and NE contractions (42 +/- 10% and 31 +/- 9% of controls, n = 6). Nifedipine, isosorbide, and nitroglycerin were further evaluated for the ability to reverse an established contraction (KCl 40 mmol/L); nitroglycerin was most effective in reversing RA contraction. In separate experiments, RA underwent adenoviral-mediated gene transfer with vehicle, Escherichia coli beta-galactosidase, or eNOS (eNOS, 10(10) PFU/mL x 1 hour). Transgene expression was confirmed by beta-galactosidase activity and eNOS immunohistochemistry after 40 hours of ex vivo incubation. Immunohistochemistry demonstrated recombinant NOS in adenovirus encoding bovine eNOS (Ad.CMVeNOS) RA only. Ad.CMVeNOS arteries contracted only 46.6 +/- 13.7% of controls to KCl (n = 5) and 48.2 +/- 11.4% of controls to prostaglandin F2 alpha a (10(-9) to 10(-6) M, n = 5).
Diltiazem, which is used empirically to prevent RA vasospasm, had little effect on human RA contractions (receptor-independent and receptor-dependent). Organic nitrates inhibited and reversed RA contractions. Adenoviral transfer of NOS suggests that future clinical application of gene therapy may play an important role in prevention of RA vasospasm.
与自体静脉移植物相比，动脉移植物对动脉粥样硬化具有相对抗性，因此人们对用于冠状动脉旁路移植的桡动脉（RA）移植物重新产生了兴趣。尽管目前已有改善动脉痉挛的药物治疗方法，但至少5%至10%的RA移植物仍会发生血管痉挛。我们系统地评估了钙通道阻滞剂和有机硝酸盐在体外抑制或逆转RA收缩的有效性。此外，我们研究了采用内皮型一氧化氮合酶（eNOS）进行新型基因治疗抑制RA收缩的疗效。
将28例行冠状动脉旁路移植术患者的RA节段置于器官浴槽中。在对照实验中，氯化钾（KCl，5至50 mmol/L）使张力呈剂量依赖性增加（最大张力，14.3±3.0 g，n = 7）。添加地尔硫䓬或维拉帕米对KCl收缩无显著影响（分别为对照的128±36%和88±24%）；然而，硝苯地平显著抑制KCl收缩（为对照的27±4%，P = 0.005）。去甲肾上腺素（NE，10⁻⁹至10⁻⁴ M）使张力呈剂量依赖性增加（对照环的最大张力，15.7±2.7 g，n = 8）。地尔硫䓬和维拉帕米预处理对NE收缩无显著影响（分别为对照的103±14%和90±14%）；硝苯地平显著抑制NE收缩（为对照的70±11%，P = 0.02）。硝酸异山梨酯和硝酸甘油显著抑制KCl收缩（分别为对照的47±9%和30±8%，n = 6）以及NE收缩（分别为对照的42±10%和31±9%，n = 6）。进一步评估了硝苯地平、硝酸异山梨酯和硝酸甘油逆转已确立收缩（KCl 40 mmol/L）的能力；硝酸甘油在逆转RA收缩方面最有效。在单独的实验中，RA接受了用载体、大肠杆菌β-半乳糖苷酶或eNOS（eNOS，10¹⁰ PFU/mL×1小时）进行的腺病毒介导的基因转移。体外孵育40小时后，通过β-半乳糖苷酶活性和eNOS免疫组织化学证实了转基因表达。免疫组织化学仅在编码牛eNOS的腺病毒（Ad.CMVeNOS）RA中显示出重组NOS。Ad.CMVeNOS动脉对KCl的收缩仅为对照的46.6±13.7%（n = 5），对前列腺素F2α（10⁻⁹至10⁻⁶ M，n = 5）的收缩为对照的48.2±11.4%。
经验性用于预防RA血管痉挛的地尔硫䓬对人RA收缩（非受体依赖性和受体依赖性）影响很小。有机硝酸盐抑制并逆转RA收缩。腺病毒介导的NOS基因转移表明，基因治疗在未来临床应用中可能在预防RA血管痉挛方面发挥重要作用。
