Ku D D, Guo L, Dai J, Acuff C G, Steinhelper M E
Department of Pharmacology and Toxicology, University of Alabama at Birmingham 35294, USA.
Am J Physiol. 1996 Dec;271(6 Pt 2):H2368-76. doi: 10.1152/ajpheart.1996.271.6.H2368.
Recent advances in genetic methods permit the introduction of random and defined mutations into the mouse germ line, producing novel mouse strains, some of which affect the heart and vasculature. A TTR-ANF transgenic strain of mice, which constitutively expresses a fusion gene consisting of the transthyretin promoter and the ANF structural gene, has been shown to result in a lifelong elevation of plasma atrial natriuretic factor (ANF) and a chronically lowered arterial blood pressure. However, no established method for efficient functional analysis of possible alterations in coronary vascular function in mice has been reported. In the present study, we describe an isolated mouse coronary artery preparation that permits an effective and reproducible evaluation of coronary endothelial and vascular function. Both left main and right coronary arteries (resting luminal diam 70-90 microns) were isolated and pressurized, and changes in luminal diameter were determined by videomicroscopy. The coronary pressure-luminal diameter relationship was not significantly different between TTR-ANF transgenic and nontransgenic littermates. Relaxation of coronaries to 0.1-100 nM ANF was significantly reduced in transgenic [maximum effect (Emax) = 43 +/- 10% (mean +/- SE) of 11 vessels] compared with nontransgenic (Emax = 73 +/- 7%, n = 15) mice. Similarly, the relaxant response to an endothelium-dependent dilator, acetylcholine, but not to endothelium-independent dilators sodium nitroprusside and isoproterenol, was significantly decreased in transgenic (Emax = 46 +/- 10%, n = 12) compared with nontransgenic (Emax = 85 +/- 5%, n = 14) mice. In contrast, the dose-dependent vasoconstriction to endothelin-1, KCl and the thromboxane mimetic U-46619 was not significantly different between the two groups. These results indicate that lifelong ANF elevation in mice is associated with a decreased responsiveness of coronary vasorelaxation to ANF, possibly resulting from receptor downregulation and/or desensitization. Endothelium-dependent relaxation was also significantly depressed in transgenic mouse coronary arteries, but smooth muscle-specific dilation and constriction were not affected. The present findings are consistent with previous studies of TTR-ANF transgenic mice showing that ANF regulates arterial blood pressure and vascular function.
基因方法的最新进展使得能够将随机和特定的突变引入小鼠生殖系，从而产生新型小鼠品系，其中一些会影响心脏和血管系统。一种TTR-ANF转基因小鼠品系，其组成型表达由转甲状腺素蛋白启动子和ANF结构基因组成的融合基因，已被证明会导致血浆心房利钠因子（ANF）终身升高以及动脉血压长期降低。然而，尚未有报道称存在一种有效的方法可对小鼠冠状动脉血管功能的可能改变进行高效功能分析。在本研究中，我们描述了一种分离的小鼠冠状动脉标本，它能够对冠状动脉内皮和血管功能进行有效且可重复的评估。分离出左主冠状动脉和右冠状动脉（静息管腔直径70 - 90微米）并对其加压，通过视频显微镜测定管腔直径的变化。TTR-ANF转基因小鼠和非转基因同窝小鼠之间的冠状动脉压力-管腔直径关系无显著差异。与非转基因小鼠（Emax = 73 +/- 7%，n = 15）相比，转基因小鼠（11条血管的最大效应（Emax）= 43 +/- 10%（平均值 +/- 标准误））中冠状动脉对0.1 - 100 nM ANF的舒张反应显著降低。同样，与非转基因小鼠（Emax = 85 +/- 5%，n = 14）相比，转基因小鼠（Emax = 46 +/- 10%，n = 12）中对内皮依赖性舒张剂乙酰胆碱的舒张反应显著降低，但对非内皮依赖性舒张剂硝普钠和异丙肾上腺素的舒张反应未受影响。相比之下，两组之间对内皮素-1、氯化钾和血栓素类似物U-46619的剂量依赖性血管收缩无显著差异。这些结果表明，小鼠体内ANF的终身升高与冠状动脉对ANF的血管舒张反应性降低有关，这可能是由于受体下调和/或脱敏所致。转基因小鼠冠状动脉中的内皮依赖性舒张也显著降低，但平滑肌特异性舒张和收缩未受影响。本研究结果与先前对TTR-ANF转基因小鼠的研究一致，表明ANF调节动脉血压和血管功能。
