Ghatta Srinivas, O'Rourke Stephen T
Department of Pharmaceutical Sciences North Dakota State University, Fargo, North Dakota 58105-5055, USA.
J Cardiovasc Pharmacol. 2006 Feb;47(2):175-81. doi: 10.1097/01.fjc.0000199681.35825.1d.
The present study was designed to determine if endogenous calcitonin gene-related peptide (CGRP) affects the process of nitrate tolerance development in blood vessels. Rat aortic rings were suspended in organ chambers and relaxations to nitroglycerin (10(-9) -10(-6) M) were obtained in nitrate tolerant and nontolerant rings contracted with norepinephrine (10(-7) M). Tolerance was induced by incubating the rings with (tolerant) or without (nontolerant) nitroglycerin (10(-4) M) for 90 minutes, followed by repeated rinsing for 1 hour. Some rings were treated with CGRP8-37 (10(-6) M), glyburide (10(-6) M), or iberiotoxin (10(-7) M) during the 90-minute desensitization period with nitroglycerin (10(-4) M), and were then washed out during the 1-hour rinsing period. Other rings were treated with capsaicin (10(-5) M) prior to the 90-minute desensitization period. Calcitonin gene-related peptide release was measured by radioimmunoassay. Relaxation to nitroglycerin was markedly reduced in tolerant rings, as compared with nontolerant. Incubation with CGRP8-37 (10(-6) M) specifically during the 90-minute desensitization period with nitroglycerin resulted in even greater impairment in the response to nitroglycerin in tolerant rings, even though the calcitonin gene-related peptide antagonist had been washed out before completion of the nitroglycerin dose-response curve. Similar results were obtained following depletion of calcitonin gene-related peptide stores in sensory nerves by treatment with capsaicin (10(-5) M) prior to the 90-minute desensitization period with nitroglycerin. Prior treatment with CGRP8-37 or capsaicin had no effect on the response to nitroglycerin in nontolerant rings. Incubation with glyburide (10(-6) M), but not iberiotoxin (10(-7) M), specifically during the 90-minute desensitization period, mimicked the effect of CGRP8-37 and capsaicin in tolerant rings, suggesting a role for KATP channels in the effect of calcitonin gene-related peptide. Nitroglycerin (10(-4) M) caused a greater than twofold increase over basal levels in calcitonin gene-related peptide release in nontolerant rings, which was abolished in rings treated with capsaicin and in nitrate tolerant rings. These results suggest that nitroglycerin releases calcitonin gene-related peptide from sensory nerves during the process of desensitization to nitrovasodilators, and that interference with either the release or action of endogenous calcitonin gene-related peptide during this period enhances the extent to which nitrate tolerance occurs. The finding that nitroglycerin-induced release of calcitonin gene-related peptide from sensory nerves attenuates the desensitizing effect of nitroglycerin represents a heretofore unknown event in the development of nitrate tolerance, and demonstrates a novel role for calcitonin gene-related peptide in the vasculature.
本研究旨在确定内源性降钙素基因相关肽（CGRP）是否影响血管中硝酸酯耐受性的发展过程。将大鼠主动脉环悬挂于器官浴槽中，在与去甲肾上腺素（10⁻⁷M）收缩的硝酸酯耐受和非耐受环中观察对硝酸甘油（10⁻⁹ - 10⁻⁶M）的舒张反应。通过将环与（耐受组）或不与（非耐受组）硝酸甘油（10⁻⁴M）孵育90分钟诱导耐受性，随后反复冲洗1小时。在与硝酸甘油（10⁻⁴M）进行90分钟脱敏期时，一些环用CGRP8 - 37（10⁻⁶M）、格列本脲（10⁻⁶M）或iberiotoxin（10⁻⁷M）处理，然后在1小时冲洗期洗去。其他环在90分钟脱敏期之前用辣椒素（10⁻⁵M）处理。通过放射免疫测定法测量降钙素基因相关肽的释放。与非耐受环相比，耐受环中对硝酸甘油的舒张反应明显降低。在与硝酸甘油进行90分钟脱敏期期间特异性地用CGRP8 - 37（10⁻⁶M）孵育，导致耐受环中对硝酸甘油反应的更大损害，尽管在完成硝酸甘油剂量反应曲线之前降钙素基因相关肽拮抗剂已被洗去。在用辣椒素（10⁻⁵M）处理后，在与硝酸甘油进行90分钟脱敏期之前耗尽感觉神经中的降钙素基因相关肽储备后也获得了类似结果。在非耐受环中，预先用CGRP8 - 37或辣椒素处理对硝酸甘油的反应没有影响。在90分钟脱敏期期间特异性地用格列本脲（10⁻⁶M）而非iberiotoxin（10⁻⁷M）孵育，模拟了CGRP8 - 37和辣椒素在耐受环中的作用，表明KATP通道在降钙素基因相关肽的作用中起作用。硝酸甘油（10⁻⁴M）使非耐受环中降钙素基因相关肽释放比基础水平增加两倍以上，在用辣椒素处理的环和硝酸酯耐受环中这种增加被消除。这些结果表明，在对硝基血管扩张剂脱敏过程中，硝酸甘油从感觉神经释放降钙素基因相关肽，并且在此期间干扰内源性降钙素基因相关肽的释放或作用会增强硝酸酯耐受性发生的程度。硝酸甘油诱导感觉神经释放降钙素基因相关肽减弱硝酸甘油的脱敏作用这一发现代表了硝酸酯耐受性发展中迄今未知的事件，并证明了降钙素基因相关肽在脉管系统中的新作用。
