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Menzikov SA, Menzikova OV: Effect of activators and blockers of ligand-regulated ion channels on the activity of the Cl-stimulated Mg2+-ATPase of the plasma membrane fraction from bream (Abramis brama L.) brain. Biochemistry. 2002 Feb;67(2):233-9.
Effects of GABA, glycine, acetylcholine, and glutamate (agonists of the GABAa/benzodiazepine, glycine, choline, and glutamate receptors, respectively) at concentrations in the range 10 (-8)-10 (-4) M on the activity of "basal" Mg (2+)-ATPase of the plasma membrane fraction from bream brain and on its activation by Cl (-) were investigated. GABA and glycine activated "basal" Mg (2+)-ATPase activity and suppressed its activation by Cl (-). Acetylcholine and glutamate activated "basal" Mg (2+)-ATPase to a lesser extent and did not suppress the activation of the enzyme by Cl (-). The activation of "basal" Mg (2+)-ATPase by neuromediators was decreased by blockers of the corresponding receptors (picrotoxin, strychnine, benztropine mesylate, and D-2-amino-5-phosphonovaleric acid). In addition, picrotoxin and strychnine eliminated the inhibiting effect of GABA and glycine, respectively, on the Cl (-)-stimulated Mg (2+)-ATPase activity. Agonists of the GABAa/benzodiazepine receptor--phenazepam (10 (-8)-10 (-4) M) and pentobarbital (10 (-6)-10 (-3) M)--activated the "basal" Mg (2+)-ATPase activity and decreased the Cl (-)-stimulated Mg (2+)-ATPase activity. The dependence of both enzyme activities on ligand concentration is bell-shaped. Moreover, phenazepam and pentobarbital increased the "basal" Mg (2+)-ATPase activity in the presence of 10 (-7) M GABA and did not influence it in the presence of 10 (-4) M GABA and 10 (-6) M glycine. The data suggest that in the fish brain membranes the Cl (-)-stimulated Mg (2+)-ATPase interacts with GABAa/benzodiazepine and glycine receptors but not with m-choline and glutamate receptors. |
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