title: Juvenile growth reduces the influence of epithelial sodium channels on myogenic tone in skeletal muscle arterioles.
abstract: Previous studies have documented that rapid juvenile growth is accompanied by functional changes in the arteriolar endothelium, but much less is known about functional changes in arteriolar smooth muscle over this period. In this study, we investigate the possible contribution of epithelial sodium channels (ENaC) to the myogenic behaviour of arterioles at two stages of juvenile growth. The effects of the ENaC inhibitor benzamil on different levels of myogenic tone were studied in isolated gracilis muscle arterioles from rats aged 21-28 days ("weanlings") and 42-49 days ("juveniles"). ENaC subunit expression in the arteriolar wall was also determined, and the interaction between ENaC and nitric oxide (NO) in regulating vascular tone was explored by combined use of benzamil and NG-monomethyl-l-arginine (l-NMMA). At physiological pressures, both steady-state myogenic tone and the dynamic adjustments in this tone triggered by acute pressure changes were less in juvenile arterioles than in weanling arterioles. α, β and γ ENaC protein was present in arterioles at both ages, but benzamil only had an effect on myogenic tone in weanling arterioles. In these vessels, benzamil increased, rather than decreased, myogenic tone, and this effect was prevented by l-NMMA or endothelial removal. These findings suggest that although ENaC is present in gracilis muscle arterioles of both weanling and juvenile rats, it is not obligatory for the genesis of myogenic activity in these vessels at either age. However, ENaC activity can significantly modulate the level of myogenic tone through stimulation of endothelial NO release at an early stage of growth.
authors: Department of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, WV, USA.
authors: Lori S
authors: LS
authors: Kang
authors: Department of Internal Medicine/Division of Nephrology, Virginia Commonwealth University Medical Center, Richmond, VA, USA.
authors: Shyama
authors: S
authors: Masilamani
authors: Department of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, WV, USA.
authors: Matthew A
authors: MA
authors: Boegehold
mesh_terms: D000367:Age Factors; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000254:growth & development*; D053503:Epithelial Sodium Channels / Q000502:physiology*; D008297:Male; D024510:Muscle Development / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000187:drug effects / Q000254:growth & development*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D014666:Vasomotor System / Q000187:drug effects / Q000254:growth & development*; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D053503:Epithelial Sodium Channels; C013407:benzamil; D019323:omega-N-Methylarginine; D000584:Amiloride
keywords: epithelial sodium channel; juvenile growth; microcirculation; myogenic response; nitric oxide