THE EFFECTS OF MIFEPRISTONE (RU486) ON PROSTAGLANDIN DEHYDROGENASE INDECIDUAL AND CHORIONIC TISSUE IN EARLY-PREGNANCY

Prostaglandin dehydrogenase is the main inactivating enzyme for prosta glandins and therefore controls local levels of prostaglandins. Since there is some evidence that the expression of this enzyme is under pro gesterone control it is reasonable that one of the effects of antiprog estin is to reduce the concentration of this enzyme and thus increase the effective concentration of prostaglandin within tissue. We have in vestigated the amount of enzyme activity within decidua and chorionic villi from women receiving the antigestagen mifepristone (RU486) 12, 2 4 and 36 h prior to surgical abortion, and examined the effect on tiss ue concentrations of prostaglandin dehydrogenase. Women receiving mife pristone in all groups had a significant reduction in concentration of prostaglandin dehydrogenase enzyme in decidual tissue. There was also a marked reduction in prostaglandin dehydrogenase in decidual cells f ollowing RU486, as demonstrated by immunochemical methods. At this sta ge of pregnancy, prostaglandin dehydrogenase was present in abundance in cytotrophoblast cells of chorionic with but virtually absent from s yncytiotrophoblast. In chorionic villi after RU486 administration in v ivo, there were no obvious differences in prostaglandin dehydrogenase distribution or reactivity in the majority of cases.