IMIPRAMINE-INDUCED CHANGES OF BRAIN ADENOSINE TRIPHOSPHATASE ACTIVITY

Abstract— Adenosine triphosphatase (ATPase) activities of brain microsomal and synaptosomal preparations are inhibited by imipramine 5-(3'-dimethylamino propyl)-10, 11-dihy-dro-5H-dibenz (b,f) azepine] in vitro , whereas microsomal ATPase activity is stimulated and synaptosomal ATPase activity remains unaltered under in vivo imipramine treatment. The inhibition of ATPase activity can to some extent be counteracted by spermine N, N'-bis(3 aminopropyl)-1,4-butanediamine]. Determination of K_m values from double reciprocal plots (activity^-1 vs. ATP mM^-1) under drug and spermine-treated conditions appear to indicate that spermine can to some extent imparta stabilizing effect mainly on the microsomal membrane ATPase, preventing inhibition in presence of imipramine in vitro , although spermine has no effect on the already destabilized membrane ATPase. Spermine exerts a stabilizing effect on membrane ATPase possibly by increasing the affinity of the enzyme for the substrate.