title: Noradrenaline stimulation of a membrane pump in frog skeletal muscle.
abstract: Resting membrane potentials were recorded from the frog sartorius before and during exposure to noradrenaline (NA; 10(-2) M) in the presence or absence of ouabain (10(-3) M) and during manipulation of the extracellular potassium concentration. In potassium-free Ringer, NA produced no significant change in the resting membrane potential. With the extracellular potassium concentration at 2.5 or 5mM, NA caused a hyperpolarization. This reversed to a depolarization when extracellular K+ was greater than 7 mM. In all cases NA-induced changes were blocked by ouabain. These effects suggest that NA stimulates a membrane cation pump, the Na : K coupling ratio of which is affected by the available ion concentrations.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001001:Anura; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009132:Muscles / Q000378:metabolism* / Q000648:ultrastructure; D009638:Norepinephrine / Q000494:pharmacology*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium; D011894:Rana pipiens; D012964:Sodium; D013268:Stimulation, Chemical
chemical_list: D010042:Ouabain; D012964:Sodium; D000251:Adenosine Triphosphatases; D011188:Potassium; D009638:Norepinephrine