NITRIC OXIDE, EXERCISE, HYPEREMIA, AND 0XYGEN UPTAKE

一氧化氮（NO）是一种重要的血管功能生理调节剂。最近的数据表明，NO在组织耗氧量的调节中也起着重要作用。NO在人类骨骼肌充血和耗氧量中的作用尚不清楚。关于运动期间骨骼肌中no的生成是否增加，尚无明确的数据。NO是否参与人体休息和运动时骨骼肌摄氧量的调节尚不清楚。拟进行的实验将检验1)动态运动时骨骼肌NO生成是否增加；2)运动过程中骨骼肌产生NO是否与运动相关充血有关；3)内源性NO是否调节休息和运动时骨骼肌耗氧量。我们将测量精氨酸到瓜氨酸的转化，使用稳定同位素技术，作为内皮NO生产的直接指标；我们还将通过输注L-NMMA来阻断NO的合成。直接测量运动肌肉耗氧量（VO2），口腔测量全身VO2。所提出的实验设计的优势在于，我们将研究人体运动时循环控制的基本机制。这些实验结果将为NO在调节人体骨骼肌血流量和耗氧量中的机制作用提供重要的新信息。

Nitric oxide (NO) is an important physiological regulator of vascular function. Recent data indicate that NO also has a significant role in the modulation of tissue oxygen consumption. The roles of NO in skeletal muscle hyperemia and oxygen consumption in humans are unclear. There are no definitive data regarding whether NO production increases in skeletal muscle during exercise. Whether NO contributes to the regulation of skeletal muscle oxygen uptake at rest and during exercise in humans is also unclear. The proposed experiments will test 1) whether NO production in skeletal muscle increases during dynamic exercise; 2) whether NO produced during exercise in skeletal muscle contributes to the hyperemia associated with exercise; and 3) whether endogenous NO modulates skeletal muscle oxygen consumption at rest and during exercise. We will measure the conversion of arginine to citrulline, using stable isotope techniques, as a direct index of endothelial NO production; we will also use blockade of NO synthesis via infusion of L-NMMA. Exercising muscle oxygen consumption (VO2) will be measured directly and whole body VO2 will be measured at the mouth. The strength of the proposed experimental design is that we will study basic mechanisms of circulatory control during exercise in humans. The results of these experiments will provide important new information about the mechanistic role of NO in the regulation of skeletal muscle blood flow and oxygen consumption in humans.