Effect of age on electrical field stimulation (EFS)-induced endothelium-dependent vasodilation in male and female rats

Objective: The purpose of this study was to determine whether the effect of age on electrical field stimulation (EFS)-induced endothelium-dependent va sodilation was different in males and females. Methods: Young (3 month) and old (25 month) Fisher 344 rats were studied: young females (YF, n=34), you ng males (YM, n=28), old females (OF, n=19), acid old males (OM, n=24). Iso lated mesenteric resistance arteries (endothelium-intact and denuded) were pressurized, and outer diameter was monitored. EFS-response curves (0.1-8 H z) were performed in preconstricted arteries in the presence of guanethidin e. EFS responses were expressed as percent relaxation from preconstricted d iameter. Area under the curve (AUC) was calculated and comparisons were mad e using ANOVA and t-tests. Results: Males became less responsive to EFS-ind uced vasodilation with age, while responses among females were unaffected ( AUC: YM=344+/-23, OM=253+/-25, P=0.008; YF=397+/-21, OF=365+/-25, P=0.33). Endothelial denudation produced a significant decrease in EFS-induced dilat ion among all rat groups. The effect of denudation was greater in young ani mals compared to old. Incubation with the nitric oxide synthase inhibitor N omega -nitro-L-arginine (LNA) significantly decreased EFS responsiveness a mong all of the rat groups. Conclusions: EFS-induced vasodilation declines with age among males. In YF and YM endothelium-dependent EFS-induced vasodi lation is mediated by the release of endothelium-derived NO. With age, endo thelial function declines, which is likely due to a decrease in the product ion of endothelium-derived NO. A decline in endothelial-derived NO is likel y responsible for the decrease in EFS-induced vasodilation with age among m ales. (C) 2001 Elsevier Science B.V. All rights reserved.