Molecular Pharmacology, Vol 7, 40-45, Copyright © 1971 by the American Society for Pharmacology and Experimental Therapeutics

Effects of Inhibitors of (Na⁺ + K⁺)-Dependent Adenosine Triphosphatase on the Uptake of Norepinephrine by Synaptosomes

¹ Department of Pharmacology, Medical School, University of Bristol, Bristol BS8 1TD, England

The effects of various (Na⁺ + K⁺)-dependent adenosine triphosphatase inhibitors on synaptosomal adenosine triphosphatase activity and norepinephrine uptake were examined under similar conditions. Ouabain (1 mM) and oligomycin (10 µg/ml) inhibited both synaptosomal adenosine triphosphatase activity and norepinephrine uptake. However, strophanthidin (1 mM) and lower concentrations of ouabain (0.1 and 0.01 mM) inhibited adenosine triphosphatase activity to the same extent as 1 mM ouabain but did not depress the uptake of norepinephrine by synaptosomes. Thus, in these circumstances, the capacity of synaptosomes to accumulate norepinephrine is not correlated with their (Na⁺ + K⁺)-dependent adenosine triphosphatase activity. It also appears that ouabain can inhibit norepinephrine uptake by a mechanism which does not involve (Na⁺ + K⁺)-dependent adenosine triphosphatase.

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ACKNOWLEDGMENTS We would like to thank Dr. B. T. Pickering for the use of a liquid scintillation counter, obtained through a grant from the Royal Society.