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 β-adrenergic blocker) or phentolamine (an α-blocker). 3. The α-agonist, phenylephrine and the β-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 Kmfor ATP or the Vmax of the reaction.
|Original language||English (US)|
|Number of pages||6|
|Journal||Comparative Biochemistry and Physiology. Part C, Comparative|
|State||Published - 1983|
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