| Abstract: | Electric stimulation (EC) of a suspension of native synaptic membranes of rat brain cortex in the Krebs-Ringer-glucose medium revealed Ca-dependent inhibition of Na+, K+-ATPase and inhibition of transport Ca-activated, Mg-dependent ATPase. The effects observed are not induced by a change in the SH-groups of the membrane proteins and are removed by an addition of total lipids of the brain (membrane protein: lipid = 5:1) or 0.35 mM novocaine. Cyclic 3',5'-AMP in concentrations of 0.1--1.0 mM causes an inhibition (up to 50%) of Na+, K+-ATPase of native synaptic membranes. The Na+, K+-ATPase activity of purified membrane preparations is not changed either by the cyclic nucleotide, or by EC. It is assumed that depolarization of excitable membranes results in structural changes, mediated by the activation of protein kinase, and manifesting themselves as labilization of protein-lipid ratios. |
