Cyclic Adenosine 3\u27,5\u27-monophosphate And Prostaglandin E(2) During Decidualization In The Rat

Prostaglandin E{dollar}\sb2{dollar} (PGE{dollar}\sb2{dollar}) is an important mediator of implantation and decidualization during pregnancy. However, its mechanism of action in the uterus is unclear. Endometrial alkaline phosphatase (ALP) activity increases during decidualization in many species and provides a marker for assessment of cellular aspects of decidualization. The objective of this study was to examine the relationship between PGE{dollar}\sb2{dollar} and cyclic adenosine 3{dollar}\sp\prime{dollar},5{dollar}\sp\prime{dollar}-monophosphate (cAMP) during decidualization in the rat. In ovariectomized rats treated with estrogen and progesterone to sensitize the uteri for decidualization, intrauterine infusion of indomethacin, an inhibitor of endogenous PG synthesis, inhibited the increase in endometrial ALP activity, which occurred in response to phosphate buffered saline, the vehicle. The inhibition was overridden by infusion of PGE{dollar}\sb2{dollar}.;Endometrial stromal cells from sensitized uteri undergo decidualization in vitro, demonstrating an increase in ALP activity similar to that seen in vivo. Indomethacin inhibited the increase in ALP activity, whereas PGE{dollar}\sb2{dollar}, but not PGF{dollar}\sb{lcub}2\alpha{rcub}{dollar}, overrode the inhibition in vitro. Lipid soluble analogues of cAMP or substances which increased cAMP concentrations (1-methyl-3-isobutyl xanthine, cholera toxin, forskolin) caused an increase in ALP activity. PGE{dollar}\sb2{dollar} caused a concentration-dependent increase in cAMP accumulation and ALP activity. Inhibition of the capacity to synthesize cAMP with 2{dollar}\sp\prime{dollar}:5{dollar}\sp\prime{dollar}-dideoxyadenosine attenuated the increase in ALP activity caused by PGE{dollar}\sb2{dollar}, suggesting that cAMP was necessary for mediating the effect of PGE{dollar}\sb2{dollar}.;Identification of isozymes of cAMP-dependent protein kinase (PKA) mediating the effect of cAMP was assessed by using cAMP analogues directed at selective sites of PKA isozymes. Synergistic activation of ALP activity in endometrial stromal cells by pairs of analogues directed at type I and II PKA suggested that both types were functionally important during decidualization.;Direct measurements of adenylate cyclase and cyclic nucleotide phosphodiesterase activities in endometrial tissue were performed to evaluate the mechanism by which PGE{dollar}\sb2{dollar} could regulate cAMP concentrations in endometrium. The results demonstrated that PGE{dollar}\sb2{dollar} can stimulate adenylate cyclase activity; however, it remains to be established whether cyclic nucleotide phosphodiesterase is subject to regulation.;These studies conclude that cAMP is an important component of the mechanism of action of PGE{dollar}\sb2{dollar} in rat endometrial stromal cells during decidualization