Effects of GABAA-ergic ligands on Cl- transport induced by the Cl-, HCO3--ATPase from carp (Cyprinus carpio L.) brain reconstituted in proteoliposomes

A Cl-, HCO3--ATPase isolated from the plasma membranes of fish brain was reconstituted in artificial proteoliposomes. The original sensitivity to GABA(A)-ergic ligands was preserved in the reconstituted enzyme. GABA was shown to activate the liposome-embedded enzyme in a concentration range from 10 to 100 mu M while picrotoxin (100 mu M) removed this activating affect. A Cl--sensitive fluorescent probe (MEQ) was used to study the ATP-dependent Cl- transport through the membrane of the proteoliposomes. ATP (in concentrations of 1.5 mM and higher) was found to induce Cl--transport into the proteoliposomes. This ATP-dependent transport was increased in the presence of GABA (100 mu M), while the latter effect could also be blocked by picrotoxin (100 mu M). It was concluded that the Cl-, HCO3--ATPase could be involved in ATP-dependent Cl--transport and regulated by activators and blockers of GABA(A) receptors.