ATP hydrolysis and noradrenaline transport in purified vesicles from splenic nerve trunk.

Abstract

AbstractA fraction of highly purified noradrenaline (NA) storage vesicles isolated from bovine splenic nerve trunk was tested for ATP hydrolytic activity. At 37.5† C and pH 7.2, the specific activity of Mg++‐ and Ca++‐activated hydrolyses were 0.22 and 0.15 μM P1/mg protein/min, respectively. There was no hydrolysis in the absence of divalent cations. The additions of various combinations of Na+ and K+ salts had little effect. Concentrations of NA and dopamine between 0.1 and 10.0 μg/ml had no effect. A concentration of 5×10‐8 M reserpine, which produced 30–50% inhibition of NA exchangeability and influx rate, had no effect on ATP hydrolysis under a wide variety of conditions. This concentration of drug causes no obvious evidence of vesicle damage at the electron microscopic level. The data do not support the possibility of a link between ATP hydrolysis and NA transport in either direction across the membrane of the isolated nerve trunk vesicle.