Effect of HCO3(-) ions on the ATP-dependent GABA(A) receptor-coupled Cl(-) channel in rat brain plasma membranes.
We studied the effect of Cl(-) (10-75 mM) and HCO(3)(-) ions (10-25 mM) on the ATP-dependent GABA(A) receptor-coupled Cl(-) channel (Cl(-)-ATPase) in rat brain plasma membranes. The total enzyme activity was detected in the presence of both anions at a Cl(-)/ HCO(3)(-) ratio of 5:1 (Cl(-), HCO(3)(-)-ATPase). Specific inhibitors of P-type transport ATPases (N-ethylmaleimide, o-vanadate, and oligomycin) suppressed Cl(-), HCO(3)(-)-ATPase, while the Cl(-)- and HCO(3)(-)-ATPase activities were low sensitive to these ligands. Bicuculline abolished the activating effect of Cl(-) and HCO(3)(-) ions on the enzyme. HCO(3)(-) ions had no effect on the ATP-dependent Cl(-) transport into proteoliposomes (with the involvement of reconstituted ATPase). In experiment with Cl(-)-preloaded liposomes, addition of HCO(3)(-) ions to the incubation medium caused the reversion of Cl(-) transport (ion efflux from liposomes). Our results suggest that HCO(3)(-) ions play an important role in the modification of properties of the ATP-dependent GABA(A) receptor-coupled Cl(-) channel and GABA(A) receptor-induced Cl(-)/ HCO(3)(-) exchange. These ions are probably involved in GABA(A) receptor-induced Cl(-)/ HCO(3)(-) exchange in neuronal membranes.
State Research Institute of General Pathology and Pathological Physiology, Russian Academy of Medical Sciences, Moscow, Russia. menzikov@mail.ru
S A
SA
Menzikov
M N
MN
Karpova
M V
MV
Kalinina
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D001640:Bicuculline / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D002540:Cerebral Cortex / Q000201:enzymology / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology; D011510:Proteolipids / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000378:metabolism*
D001639:Bicarbonates; D002712:Chlorides; D058787:GABA-A Receptor Antagonists; D011510:Proteolipids; D011963:Receptors, GABA-A; C020485:proteoliposomes; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D001640:Bicuculline