Cyclic adenosine monophosphate-induced changes in the surface morphology of diapausing blastocysts and the effects on implantation.

Estrogen induces blastocyst implantation in diapausing female mice, increases uterine levels of adenyl cyclase and cyclic adenosine monphosphate (cylic AMP), and stimulates synthesis of ribonucleic acid and protein in both the uterus and blastocyst. Furthermore, the surface ultrastructure of trophoblast cells seen with scanning electron microscopy (SEM) changes with activation of the diapausing blastocyst by estrogen. Cyclic AMP-activated blastocysts were investigated with the use of SEM and compared to blastocysts activated by estrogen. Intraperitoneal administration of cyclic AMP was generally ineffective, whereas administration of cyclic AMP intraluminally in the uterus effectively mimicked the early estrogen activation. These findings are discussed in relation to other known activation changes in preimplantation blastocysts and with regard to similar findings after administration of various antiestrogens.