Increased superoxide dismutase and Na+, K+-ATPase activities in aortic strips from potassium-adapted rats: implication for altered vascular reactivity.
The contributions of superoxide dismutase (SOD) and Na(+), K(+)-ATPase to the altered vascular reactivity in potassium-adapted rats were investigated to test the hypothesis that smooth muscle hyperpolarisation may be involved. Isometric contractions to noradrenaline (NA), 5-hydroxytryptamine (5-HT), and relaxations to acetylcholine (ACh), levcromakalim (LEV) and sodium nitroprusside (SNP), were measured in aortic rings from potassium-adapted rats. Pieces of the aortae were also excised from the animals and assayed for SOD and Na(+), K(+)-ATPase. Maximum contractile responses were significantly attenuated (P<0.05) in aortic rings from the potassium-adapted rats to NA and 5-HT, while relaxations were also significantly augmented (P<0.05) in the same rings to LEV and SNP, but not to ACh. Both SOD and Na(+), K(+)-ATPase activities were significantly higher (P<0.05) in the aortae from the potassium-adapted rats compared to controls. It is concluded that the alteration in vascular smooth muscle reactivity may be due to hyperpolarisation caused by the activities of SOD and Na(+), K(+)-ATPase.
Ozolua
Raymond I
RI
Department of Pharmacology, Faculty of Pharmacy, University of Benin, P.M.B. 1154, Benin City, Nigeria. ozolua@uniben.edu
Omogbai
Eric K I
EK
Ebeigbe
Anthony B
AB
Asagba
Samuel O
SO
D000109:Acetylcholine / Q000494:pharmacology; D000222:Adaptation, Physiological / Q000187:drug effects*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000201:enzymology*; D019806:Cromakalim / Q000494:pharmacology; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000503:physiopathology; D009599:Nitroprusside / Q000494:pharmacology; D017419:Potassium, Dietary / Q000008:administration & dosage*; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism*; D014665:Vasodilator Agents / Q000494:pharmacology
D017419:Potassium, Dietary; D014665:Vasodilator Agents; D019806:Cromakalim; D009599:Nitroprusside; D013482:Superoxide Dismutase; D000254:Sodium-Potassium-Exchanging ATPase; D000109:Acetylcholine