title: Potassium-induced relaxation in vascular smooth muscle of ground squirrels and rats.
abstract: This study was designed to assess differences in potassium-induced relaxation in two rodents, the Sprague-Dawley albino rat and the 13-lined ground squirrel, Citellus tridecimlineatus. Femoral arteries from both species were cut into helical strips for isometric force recording. After norepinephrine-induced contraction in potassium-free solution, the arterial strips relaxed in response to the introduction of potassium (0.25-20 mM) into the bath. Potassium-induced relaxation was greater in rat than ground squirrel arteries. The concentrations required to induce half-maximal relaxation were approximately 2.5 mM for both species. Potassium-induced relaxation varied with the duration of incubation in potassium-free solution, and with the contractile magnitude induced by varying norepinephrine concentrations. Ouabain inhibited potassium-induced relaxation, with the ground squirrel showing greater sensitivity to the cardiac glycoside than did the rat. Acute cooling (from 37 to 17 degrees C) caused a reduction of the contractile response to norepinephrine in rat arteries, whereas those taken from ground squirrels maintained contractions at, or above, those attained at 37 degrees C. In addition, potassium-induced relaxation in ground squirrel vessels was more sensitive to inhibition by cold than it was in those from the rat. The results show that the characteristics of potassium-induced relaxation (ouabain and temperature sensitivity, magnitude of response, etc.) are species related (ground squirrel vs. rat).
mesh_terms: D000818:Animals; D005260:Female; D005263:Femoral Artery / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012589:Sciuridae; D013045:Species Specificity; D013696:Temperature
chemical_list: D011188:Potassium; D009638:Norepinephrine