J Appl Physiol 97: 748, 2004;
doi:10.1152/japplphysiol.00518.2004
8750-7587/04 $5.00
COMMENTARY
HIGHLIGHTED TOPICS
Skeletal and Cardiac Muscle Blood Flow
Commentary
In the first featured article in this issue, entitled "Comparison of resistance and conduit vessel nitric oxide-mediated vascular function in vivo: effects of exercise training," Dr. Daniel Green and colleagues (1) examine the influence of exercise on vascular function and structure. In humans with impaired endothelial function, exercise training improves vascular function in the arteries feeding skeletal and cardiac muscles. As the results of numerous training studies have demonstrated, resistance vessel function improves following intra-arterial infusion of endothelium-dependent agonists. Similarly, enhanced flow-mediated dilation of conduit arteries is mediated largely by the endothelium. Recent animal studies suggest that larger vessels, exposed to higher shear stress forces, possess greater capacity for nitric oxide production and that shear stress-mediated nitric oxide production, although important in arteriogenesis, may not be obligatory in angiogenesis. Such findings indicate that the nature or extent of training-induced changes in vascular function and structure may be vessel bed specific. These investigators examined this possibility in a diverse group of human subjects with cardiovascular disease who exhibited a broad range of vascular dysfunction. All subjects underwent conduit and resistance vessel assessments in a randomized trial of exercise training. Although improvements were observed in both resistance and conduit vessel measures of endothelium-dependent vasodilatation, there was no correlation between these vascular beds with regard to the degree of improvement in vascular function. These results indicate that noninvasive conduit vessel measurement does not serve as a surrogate for global assessment of endothelial function in vivo. These results also support the evolving hypothesis that the mechanisms responsible for training-induced adaptations in the vasculature differ with the vascular territories involved.
A growing body of evidence points to the importance of gender differences in cardiovascular function. In the second featured article, entitled "Role of estrogen in nitric oxide- and prostaglandin-dependent modulation of vascular conductance during treadmill locomotion in rats," Drs. J. Rogers and D. Sheriff (2) studied cardiovascular responses both at rest and during exercise across a wide range of natural and experimentally induced changes in gender-related factors. The overall aims of this study were to assess the functional importance of gender-related factors and to elucidate specific signaling pathways along which gender differences are expressed. These investigators employed an integrated approach in which the influence of specific factors was examined during whole animal exercise, where many diverse physiological processes were free to act. Experiments were conducted on normal male and female rats and on ovariectomized female rats with or without estrogen supplementation. Analyses took into account gender, ovary status, and plasma estradiol levels across all animals. This study examined the importance of the nitric oxide and prostacyclin signaling pathways on various cardiovascular variables using appropriate blocking agents. The investigators found that, beyond simple gender differences in responses, specific signaling pathways could account for the differing impact of gender, ovary status, and estradiol levels on blood pressure, blood flow, and muscle vascular conductance.
Gary C. Sieck
Journal of Applied PhysiologyAugust 2004, Volume 97
REFERENCES
- Green DJ, Walsh JH, Maiorana A, Burke V, Taylor RR, and O'Driscoll JG. Comparison of resistance and conduit vessel nitric oxide-mediated vascular function in vivo: effects of exercise training. J Appl Physiol 97: 749–755, 2004.[Abstract/Free Full Text]
- Rogers J and Sheriff DD. Role of estrogen in nitric oxide- and prostaglandin-dependent modulation of vascular conductance during treadmill locomotion in rats. J Appl Physiol 97: 756–763, 2004.[Abstract/Free Full Text]
Copyright © 2004 by the American Physiological Society.
