Department of Physiology, University of Valencia, Valencia, Spain; INCLIVA Biomedical Research Institute, Hospital Clínico Universitario, Valencia, Spain.
Exp Gerontol. 2013 Nov;48(11):1329-37. doi: 10.1016/j.exger.2013.08.003. Epub 2013 Aug 13.
The present study investigated the time-course for aging-associated effects on contractile and relaxing vascular responses and nitric oxide (NO) production in the aorta from female senescence-accelerated resistant (SAMR1) and prone (SAMP8) mice. Both SAMR1 and SAMP8 were studied at three different ages: 3 (young), 6 (middle age) and 10 (old) months. Concentration-response curves to phenylephrine (10(-8) to 10(-5) M) or acetylcholine (10(-9) to 10(-5) M) were performed in the aortic rings in the absence or in the presence of NO synthase (NOS) inhibitor L-NAME (10(-4) M). Protein and gene expression for endothelial NOS (eNOS) was determined by immunofluorescence, Western blot and real-time PCR. Although we have not seen any difference in vascular responses when comparing both strains at 3 months old, we found a significant aging-associated impairment of vascular reactivity that follows a distinct time-course in SAMR1 and SAMP8. In SAMR1, increases in phenylephrine contraction and decreases in acetylcholine relaxation were only seen at 10 months old, while SAMP8 displays altered responses at 6 months that are further impaired at 10 months old. L-NAME treatment enhanced phenylephrine contractions and completely inhibited acetylcholine relaxations in all age groups of SAMR1 and SAMP8. However, the magnitude of increase in phenylephrine contraction by L-NAME was markedly reduced by aging and followed a faster pace in SAMP8. Similar pattern of responses was observed in the time course for changes of eNOS expression, suggesting an earlier and more pronounced aging-associated decrease of NO production and eNOS expression in SAMP8. These results reveal that aging enhances contractile responses to phenylephrine and decreases endothelium-dependent relaxation to acetylcholine in the aorta from female mice by a mechanism that involves a decrease of NO production. This process occurs earlier in the aorta from SAMP8 mice, establishing these mice as suitable model to study cardiovascular aging in a convenient and standard time course.
本研究旨在探讨衰老相关效应对雌性快速老化品系 1（SAMR1）和快速老化品系 8（SAMP8）小鼠主动脉收缩和舒张血管反应及一氧化氮（NO）产生的时程影响。SAMR1 和 SAMP8 分别在 3（年轻）、6（中年）和 10（老年）个月三个不同年龄段进行研究。在不存在或存在一氧化氮合酶（NOS）抑制剂 L-NAME（10⁻⁴ M）的情况下，对主动脉环进行苯肾上腺素（10⁻⁸ 至 10⁻⁵ M）或乙酰胆碱（10⁻⁹ 至 10⁻⁵ M）浓度-反应曲线的测定。通过免疫荧光、Western blot 和实时 PCR 测定内皮型一氧化氮合酶（eNOS）的蛋白和基因表达。尽管我们在比较 3 个月龄时的两种菌株时没有发现血管反应有任何差异，但我们发现，SAMR1 和 SAMP8 的血管反应性随时间的推移而显著衰老相关损伤，具有明显的时间进程。在 SAMR1 中，只有在 10 个月大时才会出现苯肾上腺素收缩增加和乙酰胆碱舒张减少，而 SAMP8 在 6 个月大时就显示出改变的反应，在 10 个月大时进一步受损。在所有年龄组的 SAMR1 和 SAMP8 中，L-NAME 处理均增强了苯肾上腺素的收缩作用，并完全抑制了乙酰胆碱的舒张作用。然而，L-NAME 引起的苯肾上腺素收缩增加幅度随着衰老而显著降低，并且在 SAMP8 中速度更快。在 eNOS 表达变化的时间过程中观察到了类似的反应模式，表明在 SAMP8 中，NO 产生和 eNOS 表达的衰老相关减少更早且更为明显。这些结果表明，衰老通过降低一氧化氮（NO）的产生，增强了雌性小鼠主动脉对苯肾上腺素的收缩反应，并降低了对乙酰胆碱的内皮依赖性舒张反应。这一过程在 SAMP8 小鼠的主动脉中发生得更早，这使得这些小鼠成为研究心血管衰老的合适模型，可以在方便和标准的时间过程中进行研究。
