Which prostanoid metabolites should be determined for the study of reproductive processes?

The non-enzymatic metabolites of prostacyclin (PGI2) and thromboxane A2 (TXA2), 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha) and thromboxane B2 (TXB2), and their 2,3-dinor metabolites, 2,3-dinor-6-keto-PGF1alpha and 2,3-dinor-TXB2, were measured in early morning urine samples in 24 in vitro fertilization (IVF) cycles in 24 women and in 27 women who became pregnant after IVF and embryo transfer (ET). The sum of the non-enzymatic metabolites and their 2,3-dinor metabolites was considered to be a reflection of total PGI2 and total TXA2 production in vivo. Both the ratio of 'total' PGI2/'total' TXA2 and the ratio of the 2,3-dinor metabolites were calculated. TXB2 concentrations showed virtually no change and the ratios of the non-enzymatic metabolites of PGI2 and TXA2 versus their 2,3-dinor metabolites remained relatively constant. As a consequence, the ratio of 2,3-dinor-6-keto-PGF1alpha/2,3-dinor-TXB2 was a close reflection of the ratio of 'total' PGI2/'total' TXA2, although the latter ratio was significantly higher all the time. We conclude that for comparative studies on the balance between PGI2 and TXA2 in IVF cycles and during gestation, the determination of the 2,3-dinor metabolites alone can replace the measurement of all four metabolites.