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Title: Kinetic characteristics of hamster (Mesocricetus auratus) brown fat (Na+/K+)-ATPase: effects of catecholamines. Author: Hettinger DR, Horwitz BA. Journal: Comp Biochem Physiol C Comp Pharmacol Toxicol; 1983; 74(2):355-60. PubMed ID: 6133689. Abstract: 1. The (Na+/K+)-ATPase activity of brown fat membranes is increased by norepinephrine, the physiological mediator of thermogenesis in this tissue. 2. This increased ATPase activity was inhibited approximately 50% by either propranolol (a beta-adrenergic blocker) or phentolamine (an alpha-blocker). 3. The alpha-agonist, phenylephrine and the beta-agonist, isoproterenol, also stimulated the ATPase activity. 4. That these latter effects were receptor-specific is supported by the finding that: (a) l(-)isoproterenol stimulation was inhibited by propranolol but not by phentolamine; (b) d(+)isoproterenol had no stimulatory effect on the ATPase activity; and (c) the l(-)phenylephrine-induced increase was inhibited by phentolamine but not by propranolol. 5. (-)norepinephrine, l(-)isoproterenol and l(-)phenylephrine all decreased the apparent Km for K+ of the (Na+/K+)-ATPase but did not alter the apparent Km for ATP or the Vmax of the reaction.[Abstract] [Full Text] [Related] [New Search]