Maternal plasma prostaglandin E2 metabolite levels during human pregnancy and parturition

Because of methodological problems associated with the measurement in biological fluids of both prostaglandin E2 (PGE2) and its unstable principal circulating metabolite 13,14-dihydro-15-keto-PGE2 (PGEM), there is little reliable information on these prostaglandins in human pregnancy and parturition. The recent discovery of a stable PGEM degradation product 11-deoxy-13,14-dihydro-15-keto-11 beta, 16 epsilon-cyclo-PGE2 (bicyclo-PGEM) has provided a means of studying endogenous plasma levels of PGEM which circumvents the problems encountered with direct measurements of PGE2 and PGEM. Using a radioimmunoassay for bicyclo-PGEM we have therefore determined maternal peripheral plasma PGE2 metabolite levels during human gestation. PGE2 metabolite levels did not alter significantly during the second or third trimesters nor during labour. This contrasts with maternal peripheral plasma levels of the principal circulating metabolite of PGF2 alpha 13,14-dihydro-15-keto-PGF2 alpha (PGFM) which increases several fold during labour. Compared to PGE2 therefore, PGF2 alpha may be quantitatively the more significant prostaglandin associated with human parturition.