title: Neurotensin decreases high affinity [3H]-ouabain binding to cerebral cortex membranes.
abstract: Previous work from this laboratory showed the ability of neurotensin to inhibit synaptosomal membrane Na(+), K(+)-ATPase activity, the effect being blocked by SR 48692, a non-peptidic antagonist for high affinity neurotensin receptor (NTS1) [López Ordieres and Rodríguez de Lores Arnaiz 2000; 2001]. To further study neurotensin interaction with Na(+), K(+)-ATPase, peptide effect on high affinity [(3)H]-ouabain binding was studied in cerebral cortex membranes. It was observed that neurotensin modified binding in a dose-dependent manner, leading to 80% decrease with 1 × 10(-4)M concentration. On the other hand, the single addition of 1 × 10(-6)M, 1 × 10(-5)M and 1 × 10(-4)M SR 48692 (Sanofi-Aventis, U.S., Inc.) decreased [(3)H]-ouabain binding (in %) to 87 ± 16; 74 ± 16 and 34 ± 17, respectively. Simultaneous addition of neurotensin and SR 48692 led to additive or synergic effects. Partial NTS2 agonist levocabastine inhibited [(3)H]-ouabain binding likewise. Saturation assays followed by Scatchard analyses showed that neurotensin increased K(d) value whereas failed to modify B(max) value, indicating a competitive type interaction of the peptide at Na(+), K(+)-ATPase ouabain site. At variance, SR 48692 decreased B(max) value whereas it did not modify K(d) value. [(3)H]-ouabain binding was also studied in cerebral cortex membranes obtained from rats injected i. p. 30 min earlier with 100 μg and 250 μg/kg SR 48692. It was observed that the 250 μg/kg SR 48692 dose led to 19% decrease in basal [(3)H]-ouabain binding. After SR 48692 treatments, addition of 1 × 10(-6)M led to additive or synergic effect. Results suggested that [(3)H]-ouabain binding inhibition by neurotensin hardly involves NTS1 receptor.
authors: Instituto de Biología Celular y Neurociencias Prof. E. De Robertis, CONICET-UBA, Facultad de Medicina, Universidad de Buenos Aires, Junín 956, 1113-Buenos Aires, Argentina.
authors: Carina
authors: C
authors: Rosin
authors: María Graciela López
authors: MG
authors: Ordieres
authors: Georgina Rodríguez de Lores
authors: GR
authors: Arnaiz
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism*; D008297:Male; D009496:Neurotensin / Q000494:pharmacology*; D010042:Ouabain / Q000378:metabolism*; D010880:Piperidines / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D011720:Pyrazoles / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018028:Receptors, Neurotensin / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D010880:Piperidines; D011720:Pyrazoles; D011804:Quinolines; D018028:Receptors, Neurotensin; C079087:SR 48692; D009496:Neurotensin; D010042:Ouabain; C047340:levocabastine