Does formyl-methionyl-leucyl-phenylalanine exert a physiological role in labor in women?

The classical chemotactic receptor for N-formyl peptides has traditionally been associated with polymorphonuclear and mononuclear phagocytes; however, several recent reports indicate that this receptor is also expressed in no n-myeloid cells. In this study we have investigated the presence of binding sites for formyl-methionyl-leucyl-phenylalanine (fMLP) in human amniotic m embranes of laboring and nonlaboring women; we have also evaluated the effe ct of the peptide on prostaglandin E (PGE) release from the same tissue. Ou r results demonstrate the presence of specific, saturable binding sites for 3H-fMLP; Scatchard plot analysis suggests the presence of both high- and l ow-affinity binding sites in laboring amnion, while only the low-affinity r eceptors were evident in nonlaboring tissue. N-t-butoxycarbonylmethionyl-le ucyl-phenylatanine (Boc-MLP), a formyl peptide receptor antagonist, inhibit ed H-3-fMLP binding in both preparations. In addition, fMLP was able to sig nificantly increase PGE synthesis in perifused amnion fragments from labori ng and nonlaboring women. This effect was counteracted by Boc-MLP treatment . The presence of specific binding sites for fMLP in amniotic tissue and th eir differing expression in laboring versus nonlaboring membranes, together with the action of the peptide on PGE synthesis, all suggest a physiologic al role for fMLP in labor.