Specific binding of 3H-ICI 198,615, a potent LTD4 antagonist, to guinea pig cardiac ventricular membranes.
Peptido-leukotrienes (LTs) elicit myocardial depression in several mammalian species, and radioligand binding assays with 3H-LTC4 and 3H-LTD4 have provided evidence of putative receptor sites on guinea pig cardiac ventricular membranes (GPCVM). Our objective was to characterize specific binding of 3H-ICI 198,615, a potent and selective LTD4 antagonist, to the 155,000 X g pellet of GPCVM. 3H-ICI 198,615 (0.01-3.8 nM) showed high specific binding (85-90% of total), which was protein dependent, saturable (Bmax = 4914 +/- 706 fmol/mg protein, n = 3), of high affinity (Kd = 4.3 +/- 0.8 nM, n = 3) and without cooperativity. Equilibrium binding was achieved by 20 minutes and could be rapidly reversed by addition of excess unlabeled ICI 198,615 or FPL55712. Competition studies with 3H-ICI 198,615 against several LTD4 antagonists produced an order of potency: ICI 198,615 much greater than SKF102922 greater than FPL55712 greater than or equal to LY171883. Addition of divalent cations caused a concentration dependent decrease in specific binding apparently due to a reduction in affinity. Binding was not influenced by the guanine nucleotide analogs GTP gamma S and Gpp(NH)p, EDTA, or a multitude of diverse non-LT receptor agonists and antagonists. These data provide evidence supporting the existence of specific and high affinity binding sites for 3H-ICI 198,615 in GPCVM.
Falcone
R C
RC
Philadelphia College of Pharmacy and Science, Dept. of Pharmacology and Toxicology, PA 19104.
Orzechowski
R F
RF
Aharony
D
D
D000818:Animals; D002413:Cations, Divalent / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007191:Indazoles / Q000378:metabolism*; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D011720:Pyrazoles / Q000378:metabolism*; D011869:Radioligand Assay; D011971:Receptors, Immunologic / Q000378:metabolism*; D018077:Receptors, Leukotriene; D013189:SRS-A / Q000037:antagonists & inhibitors*
D002413:Cations, Divalent; D007191:Indazoles; D011720:Pyrazoles; D011971:Receptors, Immunologic; D018077:Receptors, Leukotriene; D013189:SRS-A; C054217:ICI 198615