CopyrightO 1984by The American Society for Pharmacologjand Experimental Therapeutics (Na,K)Adenosine Triphosphatase Regulation by the Sympathetic Nervous System: Effects of Noradrenergic

Effects of noradrenergic stimulation and depletion on the K-p-nitrophenyiphosphatase activity and ouabaln binding associated with (Na,K)-adenosine tnphosphatase (E.C. 3.6.1.3) were ex-amined in heart, soleus, brown adipose tissue and kIdney. Stim-ulation by repeated yohimbine or d-amphetamine increased and depletion by parenteral 6-hydroxydopamine decreased enzyme activity or ouabain binding in each tissue studied except kidney. Some increase in the parameters associated with (Na,K)-adenosine triphosphatase was seen after repeated doses of 1 mg/kg of d-amphetamine or yohimbine, with maximal effects at 2 mg/kg of yohimbine and 5 or 10 mg/kg of d-amphetamine. Stimulation was reduced by administration of alpha-i or beta noradrenergic antagonists. Repeated treatment with isoprotere-fbi, but not with phenylephrine, increased ouabain binding and enzyme activity in the heart. The decrease and recovery o