title: Potassium relaxation of vascular smooth muscle from spontaneously hypertensive rats.
abstract: Helical strips of tail artery from spontaneously hypertensive (SHR) and Kyoto Wistar normotensive rats (WKY) were observed to relax in response to potassium after contraction induced by norepinephrine in potassium-free solution. Helical strips from SHR consistently showed greater relaxation in response to the addition of potassium than did those from WKY. The amplitude of potassium-induced relaxation is believed to be an index of the activity of electrogenic sodium-potassium transport and hence of sodium-potassium ATPase. Thus, the sodium-potassium ATPase activity of SHR vascular smooth muscle is increased as compared to WKY. This interpretation is supported by the observation that ouabain eliminated potassium-induced relaxation in both SHR and WKY strips. Potassium-induced relaxation in SHR was more sensitive to ouabain inhibition than in WKY. Relaxation induced by potassium in SHR and WKY strips was also shown to vary with: (1) the length of incubation in potassium-free solution, and (2) the concentration of potassium added back. The results of these experiments on potassium-induced relaxation serve as evidence that SHR have either an increased intrinsic sodium-potassium ATPase activity, or an enzyme activity that has been stimulated to a greater degree by an elevated intracellular sodium concentration which resulted from the incubation in potassium-free solution.
mesh_terms: D000818:Animals; D001158:Arteries / Q000187:drug effects* / Q000201:enzymology; D005260:Female; D006973:Hypertension / Q000503:physiopathology*; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000201:enzymology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium