Symons J David, Hayashi Yoko, Ensunsa Jodi L
University of Utah, College of Health, 250 S 1850 E Rm 241, Salt Lake City, UT 84112, USA.
J Appl Physiol (1985). 2003 Oct;95(4):1638-47. doi: 10.1152/japplphysiol.01168.2002. Epub 2003 Jun 20.
We hypothesized that myocardial contractile function and coronary arterial function are greater after ischemia and reperfusion in high-intensity treadmill-trained vs. sedentary rats. Rats performed 10 x 4-min bouts of treadmill running consisting of 2 min at 13 m/min + 2 min at 45-60 m/min (Etr) or were sedentary (Sed) for 12 wk. Animals then were instrumented to measure left ventricular (LV) contractility in response to three 15-min coronary occlusion (O) and 5-min reperfusion (R) cycles (Isc) or a sham operation (Sham). After the Isc and Sham protocols, hearts were excised and coronary arterial ( approximately 105 microm ID) function was evaluated by using isometric techniques. LV developed pressure, the first derivative of LV pressure at a developed pressure of 40 mmHg, and systolic blood pressure were not different between Etr (n = 14) and Sed (n = 7) rats before or after the Sham protocol. Furthermore, hemodynamic variables were similar in Etr (n = 14) and Sed (n = 13) animals before the Isc protocol and were depressed to the same degree by the three O-R cycles. Therefore, Etr did not alter myocardial contractile function in rats that were (i.e., Isc) or were not (i.e., Sham) exposed to ischemia and reperfusion. Acetylcholine-evoked relaxation (10-8 to 3 x 10-5 M) was greater (P < 0.05) in coronary arteries from Sham-Etr vs. Sham-Sed animals (5 of 8 doses tested) and Isc-Etr vs. Isc-Sed rats (3 of 8 doses tested). Maximal relaxation produced by sodium nitroprusside (10-4 M) was similar among groups. Vasocontractile responses produced by KCl (10-100 mM) and endothelin-1 (10-11-10-4 M) were greater (P < 0.05) in the presence vs. the absence of nitric oxide synthase inhibition (10-6 M NG-monomethyl-l-arginine) in vessels from Sham-Etr but not Sham-Sed rats and from Isc-Etr but not Isc-Sed rats. These findings suggest that Etr-evoked improvements in coronary function are maintained in small arteries even when exposed to ischemia and reperfusion.
我们假设，与久坐不动的大鼠相比，高强度跑步机训练的大鼠在缺血再灌注后心肌收缩功能和冠状动脉功能更强。大鼠进行10次4分钟的跑步机跑步，包括以13米/分钟跑2分钟 + 以45 - 60米/分钟跑2分钟（Etr），或久坐不动（Sed）12周。然后对动物进行仪器植入，以测量左心室（LV）对三个15分钟冠状动脉闭塞（O）和5分钟再灌注（R）周期（Isc）或假手术（Sham）的收缩性反应。在Isc和Sham方案后，取出心脏，使用等长技术评估冠状动脉（内径约105微米）功能。在Sham方案前后，Etr组（n = 14）和Sed组（n = 7）大鼠的左心室舒张末压、左心室压力在40 mmHg舒张末压时的一阶导数以及收缩压并无差异。此外，在Isc方案前，Etr组（n = 14）和Sed组（n = 13）动物的血流动力学变量相似，并且三个O - R周期使其降低程度相同。因此，Etr并未改变经历（即Isc）或未经历（即Sham）缺血再灌注的大鼠的心肌收缩功能。在Sham - Etr组与Sham - Sed组动物（测试的8个剂量中的5个）以及Isc - Etr组与Isc - Sed组大鼠（测试的8个剂量中的3个）中，乙酰胆碱诱发的舒张（10 - 8至3×10 - 5 M）更大（P < 0.05）。硝普钠（10 - 4 M）产生的最大舒张在各组之间相似。在Sham - Etr组而非Sham - Sed组大鼠以及Isc - Etr组而非Isc - Sed组大鼠的血管中，在存在与不存在一氧化氮合酶抑制（10 - 6 M N - 单甲基 - L - 精氨酸）的情况下，KCl（10 - 100 mM）和内皮素 - 1（10 - 11 - 10 - 4 M）产生的血管收缩反应更大（P < 0.05）。这些发现表明，即使暴露于缺血再灌注，Etr诱发的冠状动脉功能改善在小动脉中仍得以维持。
