HYDROLYSIS OF ATP AND UPTAKE OF AMINES BY SPLENIC NERVE GRANULES

1. Homogenates of splenic sympathetic nerves from cattle were used to prepare, by density gradient centrifugation, a specific granule fraction (III), which contains 843±149 ng noradrenaline/mg protein. This fraction did not show any appreciable fumarase activity. 2. Incubation of the granule fraction in the presence of noradrenaline (5×10-5 M) resulted in a nearly doubled noradrenaline content if Mg++ (2.5 mM) and ATP (5 mM) were added. The addition of Ca++ (2.5 mM) and ATP (5 mM), on the contrary, did not increase the noradrenaline content of the granules. 3. The ATPase activity of nerve granules can be stimulated to the same degree by Mg++ (Km=1.92) and Ca++ (Km=1.93 mM). A combination of both cations additively activated the hydrolysis of ATP. In the presence of Mg++ this ATPase is neither stimulated by Na+ (30 mM) and K+ (20 mM) nor inhibited by ouabain (10-4 M). 4. The ATPase activity of an unspecific fraction (I) obtained from splenic nerve homogenates could be stimulated to a greater extent by Ca++ (Km=1.09 mM) than by Mg++ (Km=3.00 mM). The ATPase of fraction I showed a maximal velocity of reaction higher than that that of fraction III. 5. The uptake of noradrenaline and the hydrolysis of ATP were inhibited by 6×10-5 M reserpine or prenylamine. N-ethylmaleimide (1.8×10-4 M) did not influence either reactions. 6. A causal relationship between amine transport and ATPase activity in the noradrenaline storing nerve granules is discussed. © 1969 Springer-Verlag.