Effect of HC[O.sub.3]-Ions on the ATP-dependent GAB[A.sub.A] receptor-coupled [Cl.sup.-] channel in rat brain plasma membranes

• Published in: Bulletin of experimental biology and medicine Vol. 152; no. 1; p. 38
• Main Authors: Menzikov, S.A, Karpova, M.N, Kalinina, M.V
• Format: Journal Article
• Language: English
• Published: Springer 01.11.2011
• Subjects: Adenosine triphosphatase; Brain
• ISSN: 0007-4888; 1573-8221

We studied the effect of [Cl.sup.-] (10-75 mM) and HCO; ions (10-25 mM) on the ATP-dependent GAB[A.sub.A] receptor-coupled [Cl.sup.-] channel ([Cl.sup.-]-ATPase) in rat brain plasma membranes. The total enzyme activity was detected in the presence of both anions at a [Cl.sup.-]/HC[O.sup.-.sub.3] ratio of 5:1 ([Cl.sup.-],HC[O.sup.-.sub.3]-ATPase). Specific inhibitors of P-type transport ATPases (N-ethylmaleimide, ovanadate, and oligomycin) suppressed [Cl.sup.-], HC[O.sup.-.sub.3]-ATPase, while the [Cl.sup.-]- and HC[O.sup.-.sub.3]-ATPase activities were low sensitive to these ligands. Bicuculline abolished the activating effect of [Cl.sup.-] and HC[O.sup.-.sub.3] ions on the enzyme. HC[O.sup.-.sub.3] ions had no effect on the ATP-dependent [Cl.sup.-] transport into proteoliposomes (with the involvement of reconstituted ATPase). In experiment with [Cl.sup.-]-preloaded liposomes, addition of HC[O.sup.-.sub.3] ions to the incubation medium caused the reversion of [Cl.sup.-] transport (ion efflux from liposomes). Our results suggest that HC[O.sup.-.sub.3] ions play an important role in the modification of properties of the ATP-dependent GAB[A.sub.A] receptor-coupled [Cl.sup.-] channel and GAB[A.sub.A] receptor-induced [Cl.sup.-]/HC[O.sup.-.sub.3] exchange. These ions are probably involved in GAB[A.sub.A] receptor-induced [Cl.sup.-]/HC[O.sup.-.sub.3] exchange in neuronal membranes. Key Words: rat brain plasma membranes; ATPase; chlorine; bicarbonate