Journal
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
Volume 293, Issue 3, Pages R1274-R1279Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpregu.00213.2007
Keywords
muscle contraction; resistance vessel; gender; arteriole
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Funding
- NCRR NIH HHS [P20 RR 016454] Funding Source: Medline
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Little is known of the vasomotor responses of skeletal muscle arterioles during and following muscle contraction. We hypothesized that aging leads to impaired arteriolar responses to muscle contraction and recovery. Nitric oxide ( NO) availability, which is age dependent, has been implicated in components of these kinetics. Therefore, we also hypothesized that changes in the kinetics of vascular responses are associated with the NO pathway. Groups were young ( 3 mo), old ( 24 mo), endothelial NO synthase knockout ( eNOS -/ -), and NG- nitroL- arginine ( L- NA)- treated male and female C57BL/ 6 mice. The kinetics of vasodilation during and following 1 min of contractions of the gluteus maximus muscle were recorded in second- order ( regional distribution) and third- order ( local control) arterioles. Baseline, peak ( during contraction), and maximal diameters ( pharmacological) were not affected by age or sex. The kinetics of dilation and recovery were not different between males and females at the young age. There was a significant slowing of vasodilation at the onset of contractions ( similar to 2- fold; P < 0.05) and a significant speeding of recovery ( similar to 5- fold; P < 0.05) in old males vs. old females and vs. young eNOS -/ -, and L- NA did not affect the kinetics at the onset of muscle contraction. eNOS -/ - mimicked the rapid recovery of old males in second- order arterioles; acute NO production ( L- NA) explained similar to 50% of this effect. These data demonstrate fundamental age- related differences between the sexes in the dynamic function of skeletal muscle arterioles. Understanding how youthful function persists in females but not males may provide therapeutic insight into clinical interventions to maintain dynamic microvascular control of nutrient supply with age.
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