Osmotic regulation of the sodium pump in rat brain synaptosomes
Mongin, A.A.; Aksentsev, S.L.; Rakovich, A.A.; Okun', N.M.; Konev, S.V.; Orlov, S.N.
Biofizika 37(5): 950-956
1992
ISSN/ISBN: 0006-3029 PMID: 1335292 Document Number: 400893
Effect of medium osmolarity on 3H-ouabain binding and the rate of ouabain-sensitive 86Rb+ transport in the rat brain synaptosomes was studied. A decrease in tonicity to 230 mOsm increases both parameters indicating the activation of the sodium pump upon synaptosome swelling. The effect is retained in the absence of inside-oriented Na+ gradient, i. e. a rise in Na(in) is not responsible for hypoosmotic activation. Colchicine (5mM) decreased and cytochalasin B (40 microM) increased the ouabain binding. In the presence of cytochalasin B the inhibition of binding observed under hypotonic conditions was shifted to higher osmolarity values. It is suggested that volume regulation of the sodium pump is controlled by the cytoskeleton elements.