PROSTAGLANDIN-E(2), CAMP AND CAMP-DEPENDENT PROTEIN-KINASE ISOZYMES DURING DECIDUALIZATION OF RAT ENDOMETRIAL STROMAL CELLS IN-VITRO

When endometrial stromal cells from rat uteri sensitized for the decid ual cell reaction are cultured in vitro, they undergo decidualization, as indicated by increased alkaline phosphatase (ALP) activity. Prosta glandin E2 (PGE2) stimulates this increase in activity. To determine t he role of cAMP in the stimulation, we examined the effect of 2':5'-di deoxyadenosine (DDA), an inhibitor of adenylate cyclase, on the abilit y of PGE2 to increase ALP activity. As indicated by [H-3]cAMP accumula tion in endometrial stromal cells preincubated with [H-3]adenine, DDA inhibited PGE2-stimulated synthesis of cAMP in a concentration-depende nt manner. Furthermore, DDA caused a significant decrease in the PGE2- induced ALP activity on day 3 of culture. Dibutyryl cAMP overrode this inhibition. The effect of DDA was not mimicked by adenosine, which ha d a stimulatory effect on ALP activity in the non-stimulated cultures and no significant effect in PGE2-stimulated cultures. Thus the inhibi tory effect of DDA on PGE2-stimulated ALP activity is unlikely to be m ediated by adenosine-related receptors. These results suggest that cAM P is an essential, but not necessarily the only, intracellular messeng er of PGE2 in endometrial stromal cells during decidualization. The is ozymes of cAMP-dependent protein kinase (PKA) mediating the effect of cAMP were assessed by using cAMP analogues directed at selective sites of PKA isozymes. Synergistic activation of ALP activity in endometria l stromal cells by pairs of analogues directed at types I and II PKA s uggested that both types were functionally important during decidualiz ation.