Sensitivity of the brain synaptosomal membrane Mg(2+)-ATPase activity to arachidonic acid is under control of the Na+,K(+)-ATPase state.

Evidence is presented for the sensitivity of the synaptosomal plasma membrane Mg(2+)-ATPase activity to arachidonic acid being dependent on the functional state of Na+,K(+)-ATPase. An "Inversion effect" was observed at arachidonic acid concentrations exceeding 80 mumol/l when the Mg(2+)-ATPase activity (after ouabain addition) is higher than the total ATPase activity (without ouabain). The "Inversion effect" is reduced by cyclooxygenase inhibitor indomethacin or acetylsalicylic acid and restored by prostaglandin PGA2 or PGD2.