• Estrus;
  • ovaries;
  • oviducts;
  • PAF receptors;
  • pregnancy

PROBLEM: This study determined platelet activating factor (PAF) binding to ovaries and oviduct tissues to identify the location of PAF–tissue interaction. METHOD: Mouse ovaries and oviducts taken during the estrous cycle and days 1, 4 and 7 post-conception (pc) were analyzed by [

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H]PAF binding using frozen sections and autoradiography. RESULTS: For the outer epithelium of estrous and metestrous ovaries there was no significant difference in PAF binding (P>0.05); however, both stages were significantly different from proestrous (P<0.001). Ovarian stroma PAF binding was significantly higher (P<0.001) at estrous than metestrous, with no PAF binding at proestrous. Binding of PAF to estrous ovarian follicles was significantly greater (P<0.001) than at proestrous and metestrous. Estrous oviduct binding of PAF was significantly increased for stroma, inner epithelium and lumen (P<0.001 in all cases). At days 1 and 7 pc, all ovarian tissues had the greatest PAF binding with day 4 pc failing to bind PAF except for a significant decrease in corpora luteal binding (P<0.001). Oviduct binding of PAF was greatest at day 1 pc. CONCLUSION: Ovarian and oviduct PAF receptor expression corresponds to peak embryo PAF synthesis and establishes the basis for PAF–PAF receptor mediated early pregnancy signaling system.