Author(s)

Sergey A. Menzikov, Marina V. Kalinina

State Research Institute of General Pathology and Pathological Physiology RAS, Moscow, Russia.

The work is a study of the influence of Ca²⁺ (0.01 - 1 mM) on neuronal CI^-, HCO₃^-, -ATPase complex: an enzyme that is a CI^--pump which is functionally and structurally coupled to GABA_A-receptors. It is found that influence of Ca²⁺ on the multifunctional complex starts at concentration of 50·M and at concentration of 0.1 mM, it reduces the “basal” one and increases the CI^-, HCO₃^-, -stimulated Mg²⁺-ATPase activities. GABA (0.1 - 100μM) activates the “basal” Mg²⁺-ATPase activity in the ab-sence of calcium. The effect of GABA on the enzyme in the presence of 0.01 ·M Ca²⁺ does not change. At the same time, 1 mM Ca²⁺eliminates the GABA effect on the “basal” Mg²⁺-ATPase activity. Competitive blocker of GABA_A-receptors bicuculline (5 - 20 μM) in the absence of Ca²⁺ ions elimi-nates the stimulation of the “basal” Mg²⁺-ATPase by anions. When 0.25 mM Ca²⁺ is added to the in-cubation medium the inhibitory bicuculline effect on the enzyme does not appear. We found that 0.1 mM o-vanadate (protein tyrosine phosphatase blocker) reduces the GABA-activated ATPase activity. At the same time, 0.1 mM genistein (a protein tyrosine kinase blocker) has no effect on enzyme activity. In the presence of Ca²⁺ (0.25 mM), the effect of o-vanadate on the “basal” and CI^-, HCO₃^-, -ATPase activities does not appear. It is shown for the first time that high concentrations of Ca²⁺prevent the action of GABA_A-ergic ligands on the study ATPase. It is assumed that there is the involvement of protein kinases and protein phosphatases in the modulation of the enzyme activity by calcium. The observed effect of calcium on the ATPase may play an important role in the study of the mechanisms of epileptogenesis and seizure activity.

Mg²⁺-ATPase, Chloride, Bicarbonate, Calcium, Rat Brain Plasma Membranes, GABA_A-Ergic Drugs, o-Vanadate, Genistein

Menzikov, S. and Kalinina, M. (2014) Effects of Calcium on the GABA_A-Coupled CI^-/HCO₃^- -ATPase from Plasma Membrane of Rat Brain. Advances in Enzyme Research, 2, 82-91. doi: 10.4236/aer.2014.22009.