title: Regulation of [3H]nitrendipine binding by phospholipases A2 and C through direct and GTP-sensitive mechanisms.
abstract: We compared the effects of Phospholipases A2, C, B and D on [3H]nitrendipine binding to hamster cardiac membranes, in the absence and presence of ATP or GTP. Phospholipase A2, competitively inhibited [3H]nitrendipine binding to hamster cardiac membranes unchanged by ATP or GTP (Ki = 5 ng/ml); as evidenced by complete and reversible displacement of [3H]nitrendipine binding and increase in KD on Scatchard analyses. Phospholipase C also completely inhibited [3H]nitrendipine binding to hamster cardiac membranes (Ki = 5 micrograms/ml) with a decrease in Bmax and no change in KD on Scatchard analyses. The addition of GTP alone inhibited the PLC effect in EGTA-treated membranes. The addition of GTP with either CaCl2 or ATP or both resulted in an equal and opposite enhancement of the PLC effect. Phospholipases B and D had no effect on [3H]nitrendipine binding. These data support: (1) Direct effect of PLA2 on dihydropyridine binding. (2) Indirect regulation of dihydropyridine binding by Phospholipase C through a GTP and ATP-sensitive mechanism.
authors.affiliation: Department of Medicine, University of Pittsburgh, Montefiore University Hospital, Pennsylvania 15213.
authors.forename: M S
authors.initials: MS
authors.lastname: Finkel
authors.forename: T L
authors.initials: TL
authors.lastname: Hartsell
authors.forename: C V
authors.initials: CV
authors.lastname: Oddis
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D015220:Calcium Channels; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D004533:Egtazic Acid / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D007700:Kinetics; D008245:Lysophospholipase / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008647:Mesocricetus; D009206:Myocardium / Q000378:metabolism*; D009568:Nitrendipine / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism* / Q000494:pharmacology; D054467:Phospholipases A2; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism*; D014316:Tritium; D010738:Type C Phospholipases / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D011978:Receptors, Nicotinic; D014316:Tritium; D004533:Egtazic Acid; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D009568:Nitrendipine; D010741:Phospholipases A; D054467:Phospholipases A2; D008245:Lysophospholipase; D010738:Type C Phospholipases; D010739:Phospholipase D