Exposure of preimplantation embryos to platelet-activating factor increases birth rate.

Problem: Platelet-activating factor (PAF) plays a significant role in fertility. Preimplantation stage embryos produce PAF (ePAF) which is required for development. PAF's mechanism of action is receptor-mediated and its presence has been reported in the developing mouse and human embryo. Exposure of preimplantation stage mouse embryos results in higher implantation rates. However, the effect of such treatment on live-birth rates and birth weights has not been reported. Therefore, the objective the study was to determine the effect of exposing preimplantation mouse embryos to PAF on subsequent birth rate and weight.

Design: Two-cell stage preimplantation stage mouse embryos exposed to PAF (10(-7) M) for 15 min prior to intraoviductal transfer.

Methods: Preimplantation stage embryos were recovered from eCG/hCG primed BDF1 female mice. Embryos were exposed to synthetic PAF (10(-7) M) for 15 min. PAF-treated embryos were transferred to the oviducts of pseudopregnant female CD-1 female mice. Superovulated and cultured BDF1 embryos not treated with PAF served as in vitro controls and naturally ovulated embryos with no collection/culture served as in vivo controls. Embryos were permitted to develop to term (18-21 days). The number of pups born per litter and litter weights subsequently were recorded.

Results: A total of 160 BDF1 mouse embryos were collected, treated, and transferred (20 per CD-1 recipient) as described. There was a significant (P < 0.05) increase in the number of pups born to the PAF treatment group (56/80; 70%) as compared to the control group (44/80; 55%). There was also a significant difference (P < 0.05) in litter birth weights between the PAF (1.31 g/litter) and controls groups (1.25 g/litter). There was a significant difference (P < 0.05) in birth weights between the PAF treatment group and the in vivo group (1.51 g/litter). There was a significant difference in birth weights between the in vitro-control and in vivo groups (1.51 g/litter). There were no observational malformaties to pups born in any group.

Conclusions: Brief exposure of preimplantation stage embryos to PAF will result in a significant increase of delivery rates (pups/litter) as well as birth weights. However, the increase of birth weight was significantly below that found naturally. Additional studies are warranted to elucidate the mechanism of PAF's action in the preimplantation stage embryo and subsequent uterine development.