title: Nitric oxide pathway counteracts enhanced contraction to membrane depolarization in aortic rings of rats on high-sodium diet.
abstract: Vascular smooth muscle cell contraction and endothelium-dependent relaxation was evaluated in aortic rings isolated from weaned, 5-mo-old Sprague-Dawley rats fed a normal (NS; 0.8% NaCl) or high (HS; 8% NaCl) sodium diet. Arterial pressure was 140 +/- 6 (NS) and 145 +/- 6 mmHg (HS). In endothelium-denuded rings, the response to phenylephrine (PE) was not modified by the sodium diet, while that of depolarizing agent KCl and intracellular calcium releasing agent caffeine increased in the HS group. When endothelium was preserved, PE-evoked contraction was reduced in both NS and HS groups, the contraction being yet lower in the HS group. This effect was partially obliterated by addition of N(G)-nitro-L-arginine methyl ester (L-NAME), independently of the sodium diet. Relaxation to ACh in intact rings and to sodium nitroprusside (SNP) and 8-bromoadenosine 3'5' cyclic guanosine monophosphate (8-BrcGMP) in the absence of endothelium was enhanced in rings isolated from HS rats. In addition, the dose-response curve to 8-BrcGMP was shifted to the right in the presence of iberiotoxin, an inhibitor of large conductance, voltage-dependent, and calcium-sensitive potassium channel (BK(Ca)). However, shift was more marked in rings from HS rats. Present results provide evidence that response of vascular smooth muscle cell to nitric oxide/cGMP-related compounds is increased in HS rings and is associated with a greater activation of the repolarizing BK(Ca) channels. Such changes might counterbalance enhanced contractile response to membrane depolarization and thus participate in maintenance of arterial pressure in the present model of early and long-term HS feeding in rats.
authors.affiliation: Groupe Rein et Hypertension, Université Montpellier I, Montpellier, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Cordaillat
authors.forename: Aurélie
authors.initials: A
authors.lastname: Fort
authors.forename: Anne
authors.initials: A
authors.lastname: Virsolvy
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Elghozi
authors.forename: Sylvain
authors.initials: S
authors.lastname: Richard
authors.forename: Bernard
authors.initials: B
authors.lastname: Jover
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology*; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D009599:Nitroprusside / Q000494:pharmacology; D010477:Perfusion; D010656:Phenylephrine / Q000494:pharmacology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage* / Q000494:pharmacology; D013696:Temperature; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D017673:Sodium Chloride, Dietary; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine; D009569:Nitric Oxide; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester