Effects of ageing and exercise training on endothelium-dependent vasodilatation and structure of rat skeletal muscle arterioles.
Ageing reduces endothelium-dependent vasodilatation in humans and animals, and in humans, exercise training reverses the ageing-associated reduction in endothelium-dependent vasodilatation. The purpose of this study was to determine the mechanism(s) by which 10-12 weeks of treadmill exercise enhances endothelium-dependent vasodilatation in muscles of differing fibre composition from young and old rats. Three- and 22-month-old male Fischer 344 rats were assigned to young sedentary, young exercise-trained, old sedentary, or old exercise-trained groups. Arterioles were isolated from the soleus and gastrocnemius muscles; luminal diameter changes were determined in response to the endothelium-dependent vasodilator acetylcholine (ACh, 10(-9)-10(-4) mol l(-1)) alone and in the presence of the nitric oxide synthase (NOS) inhibitor l-NAME (10(-5) mol l(-1)) or the combination of l-NAME and the cyclooxygenase inhibitor indomethacin (10(-5) mol l(-1)). Training ameliorated the ageing-induced reduction in endothelium-dependent vasodilatation in soleus muscle arterioles. Treatment with l-NAME alone and in combination with indomethacin abolished differences in ACh vasodilatation occurring with ageing and training. Expression of endothelial NOS (eNOS) mRNA in soleus arterioles was unaltered by ageing, whereas eNOS protein was increased with age; training elevated both eNOS mRNA and protein. In gastrocnemius muscle arterioles, ageing did not alter maximal vasodilatation, but ageing and training increased maximal arteriolar diameter. These results demonstrate that ageing-induced reductions and training-induced enhancement of endothelial vasodilatation both occur through the nitric oxide signalling mechanism in highly oxidative skeletal muscle, but ageing and training do not appear to act on the same portion of the signalling cascade.
Department of Health and Kinesiology, Texas A&M University College Station, TX 77843, USA.
Scott A
SA
Spier
Michael D
MD
Delp
Cynthia J
CJ
Meininger
Anthony J
AJ
Donato
Michael W
MW
Ramsey
Judy M
JM
Muller-Delp
D000109:Acetylcholine / Q000494:pharmacology; D000375:Aging / Q000502:physiology*; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D001835:Body Weight / Q000502:physiology; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D009599:Nitroprusside / Q000494:pharmacology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D012333:RNA, Messenger; D009599:Nitroprusside; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D002950:Citrate (si)-Synthase; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin