Circulating and urinary metabolites of PGE2 and PGF2a

Fig. 1 summarizes the structures of primary PGE₂ and PGF_2a (upper line), their initially formed 15-ketodihydro-metabolites which appera early in blood after release (middle), and their β- and ω-oxidized metabolites, which appear later and remain longer in the circulation and also dominate the urinary profile (lower line). No single compound can be put forward as the ideal assay parameter: depending on aim and design of the study, either of these compounds may be monitored. The chemical instability of PGE compounds should however be kept in mind: generally it is safer to induce degradation by alkali treatment into a stable product prior to assay.