Effects of selective and nonselective PGE2 receptor agonists on cervical tensile strength and collagen organization and microstructure in the pregnant rat at term.

Objective: The purpose of this study was to determine which of the 4 PGE2 receptors (EP1-EP4) is involved in cervical ripening in the rat, and to correlate its activity with changes in tensile strength and collagen microstructure.

Study Design: We assessed tensile strength after administration of selective and nonselective PGE2 receptor agonists. Quantification of collagen organization and microstructure was accomplished with polarized light microscopy and transmission electron microscopy.

Results: Selective agonists for EP1-3 did not produce significant differences when compared with each other or control animals. Significant differences in tensile strength, proportion of organized collagen, and microstructure were found between treatment and control animals with the nonselective receptor agonist (PGE2). This was taken as an indirect measure of EP4 activity.

Conclusion: Changes in cervical collagen organization and microstructure are quantifiable and correlate with changes in tensile strength. These data implicate EP4 as the PGE2 receptor involved in producing these changes in the rat cervix.