| Abstract: | Mg-ATPase (1 mM) induces a decrease in the intensity of light scattering (I1) at 620 nm of rat brain synaptic vesicles (SV) suspended in sucrose, with this decrease being indicative of the swelling of the vesicles. The Mg-ATPase-induced swelling appears to be associated with the function of H+-ATPase of SV membranes, since it is completely abolished by the proton pump blocker dicyclohexylcarbodiimide and the protonophore carbonylcyanide m-chlorophenylhydrazone. The Mg-ATPase-induced swelling was enhanced in the presence of the permeable anion Cl- (in the range of 25-50 mM KCl). Ca2+ (and Mg2+) at high concentrations (0.1-1.0 mM) cause aggregation of the SV as measured by changes in the I1. Colchicine and cytochalasin do not affect SV swelling and aggregation whereas Mg-ATP (1 mM) lowers aggregation caused by Ca2+ (1 mM). |
