Modulation of ligand binding to leukotriene B4 receptors on guinea pig lung membranes by sulfhydryl modifying reagents.
We investigated the mechanism and modulation of 3H-labeled leukotriene B4 (LTB4) binding to guinea pig lung membranes. [3H] LTB4 bound specifically and rapidly (Kobs = 0.06 +/- 0.006 min-1) to high affinity (Kd = 0.63 +/- 0.06 nM) and saturable (Bmax = 224 +/- 16 fmol/mg) sites without cooperativity (nH = 1.05). Bound ligand was partially (70%) dissociated with excess LTB4 or the selective antagonist U-75,302. Complete dissociation could be achieved with either LTB4 or U-75,302 in combination with 10 microM GTP gamma S. A series of structural analogs and selective antagonists inhibited binding in a competitive manner with the following order: LTB4 much greater than 20-(OH)-LTB4 greater than LTB5 greater than LTB-dimethylamide = U-75,302 greater than 12(R)-hydroxy-eicosatetraenoic acid greater than 5(S),12(S)-dihydroxy,6-trans,8-cis,10-trans,14-cis-ETE greater than 12(S)-hydroxy-eicosatetraenoic acid much greater than trans-LTB4 isomers. 5(S)-hydroxy-eicosatetraenoic acid, prostaglandins, peptide-leukotrienes and platelet-activating factor (at 10 microM each) did not inhibit, providing evidence that [3H]LTB4 bound to specific receptors on guinea pig lung membranes. N-Ethylmaleimide (NEM) and p-chloromercuriphenyl sulfonic acid (PCMP) inhibited binding (IC50 = 144 +/- 66 and 4.6 +/- 1.0 microM, respectively) in an irreversible manner, as evident by an inability to overcome the inhibition by extensive washing.(ABSTRACT TRUNCATED AT 250 WORDS)
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Department of Pharmacology, ICI Americas, Inc., Wilmington, Delaware.
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D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D005033:Ethylmaleimide / Q000494:pharmacology; D005233:Fatty Alcohols / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D006018:Glycols / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007700:Kinetics; D007975:Leukotriene B4 / Q000378:metabolism*; D008168:Lung / Q000378:metabolism*; D008297:Male; D011971:Receptors, Immunologic / Q000378:metabolism*; D018102:Receptors, Leukotriene B4; D013439:Sulfhydryl Reagents / Q000494:pharmacology*
D005233:Fatty Alcohols; D006018:Glycols; D011971:Receptors, Immunologic; D018102:Receptors, Leukotriene B4; D013439:Sulfhydryl Reagents; C062137:U 75302; D007975:Leukotriene B4; D002731:4-Chloromercuribenzenesulfonate; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D005033:Ethylmaleimide