NITRIC OXIDE, EXERCISE, HYPEREMIA, AND 0XYGEN UPTAKE

一氧化氮（NO）是血管功能的重要生理调节剂。 最近的数据表明，NO在组织耗氧量的调节中也具有重要作用。NO在人体骨骼肌充血和氧消耗中的作用尚不清楚。 关于运动过程中骨骼肌中NO的产生是否增加，目前还没有确切的数据。 NO是否有助于调节人类在休息和运动时骨骼肌的摄氧量也不清楚。 所提出的实验将测试1）在动态运动期间骨骼肌中的NO产生是否增加; 2）在骨骼肌中运动期间产生的NO是否有助于与运动相关的充血;以及3）内源性NO是否调节静息和运动期间的骨骼肌耗氧量。 我们将使用稳定同位素技术测量精氨酸向瓜氨酸的转化，作为内皮NO产生的直接指标;我们还将通过输注L-NMMA阻断NO合成。将直接测量运动肌肉耗氧量（VO 2），并在口腔测量全身VO 2。 所提出的实验设计的优势在于，我们将研究人类运动过程中循环控制的基本机制。 这些实验的结果将提供重要的新信息的机制作用的NO在调节骨骼肌血流量和氧气消耗在人类。

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.