Specific receptor sites for platelet activating factor on rat liver plasma membranes.
The binding of 3H-labeled 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine (PAF) to isolated rat liver plasma membranes and its inhibition by PAF agonists and receptor antagonists was demonstrated. The specific binding was readily saturable with a high affinity. The equilibrium dissociation constant (KD) value was 0.51 (+/- 0.14) nM and the maximal number of binding sites (Bmax) was estimated to be 141 (+/- 18) fmol/mg protein. The binding site was PAF specific-biologically inactive enantiomer was practically inactive. Two PAF-like receptor antagonists, Ono-6240 and CV-3988, and two PAF-unlike receptor antagonists, L-652,731 and kadsurenone, also displaced the binding of [3H]PAF to rat liver plasma membranes but their relative potencies in this system differed from those found in other receptor systems. Mg2+ potentiated [3H]PAF binding but inhibited it at concentrations higher than 10 mM. Both Na+ and K+ inhibited the Mg2+-potentiated binding, an ionic effect which was different from that found in rabbit platelets. These results suggest that rat livers contain PAF-specific receptors, and the receptors in rat livers are different from those found in other receptor systems.
Hwang
S B
SB
Department of Biochemical Regulation, Merck Sharp & Dohme Research Laboratories, Rahway, New Jersey 07065.
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D009994:Osmolar Concentration; D010972:Platelet Activating Factor / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled
D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D000469:Alkaline Phosphatase