Effect of training frequency on endothelium-dependent vasorelaxation in rats.
BACKGROUND
Moderate physical activity enhances endothelium-dependent vasorelaxation. Whether the frequency of exercise affects endothelial function is unclear. The purpose of this study was to investigate the effects of various frequencies of training on endothelium-dependent vasorelaxation.


METHODS
Male Wistar rats were trained for 8 weeks on a treadmill at various frequencies [1 (Ex1), 3 (Ex3) or 5 days/week (Ex5)] and compared with age-matched sedentary animals (SED). A control group allowed us to assess endothelial function before the exercise protocol. Rings of thoracic aorta were precontracted with phenylephrine.


RESULTS
Endothelium-independent relaxation elicited by sodium nitroprusside was similar in all groups. The maximal response elicited by acetylcholine (ACh) was not different between groups, whereas pD2 values (-logEC50, EC50 being the concentration of ACh that elicited 50% of the maximal response) significantly correlated with frequency of training. nitro-L-arginine methyl ester (L-NAME) reduced the relaxation elicited by 10(-7) mol/l ACh or higher in control and all trained groups, and by 10(-6) mol/l ACh or higher in SED group. Indomethacin inhibited the vasodilating response to 10(-7) mol/l ACh or higher in control, SED and Ex1 groups, and to 10(-8) mol/l or more in Ex3 and Ex5 animals. Tetraethylammonium attenuated the response to 10(-6) mol/l ACh or higher in control and SED groups and to 10(-7) mol/l or more in all trained animals.


CONCLUSIONS
This data suggest that decreased ACh-induced vasorelaxation after physical inactivity may result from impairment of endothelial nitric oxide synthase, prostacyclin and endothelium-derived hyperpolarizing factor pathways. This effect is prevented by training in a frequency-dependent manner.
Heylen
Erwan
E
EA3879, Group Vascular Endothelium, Exercise, Nutrition, Health, Brest, France.
Guerrero
François
F
Mansourati
Jacques
J
Theron
Michaël
M
Thioub
Sanéo
S
Saïag
Bernard
B
D000109:Acetylcholine / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D010805:Physical Conditioning, Animal; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D019789:Tetraethylammonium / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D009599:Nitroprusside; D010656:Phenylephrine; D019789:Tetraethylammonium; D002950:Citrate (si)-Synthase; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin