Comparative metabolism of PGFM (13,14-dihydro-15-keto-PGF2α) in feces of felids

Methods for monitoring endocrine activities are useful tools for reproduction management. In particular, captive breeding of endangered felid species is considered to be an important part of the species conservation efforts. Within breeding programs, reliable methods for pregnancy diagnosis are highly demanded to prevent peri- and postpartal losses, but pregnancy diagnosis based on gestagen metabolites in felids is hampered by pseudopregnancies. Recently, we described fecal PGFM as an indicator for pregnancy in several feline species, but peak levels of PGFM secretion differed dramatically between species. It is believed that prostaglandin composition and metabolism pathways may differ as well. Therefore, a study was devised to both compare various fecal immunoreactive PGFM metabolites and to identify prostaglandins in fecal extracts by liquid chromatography-mass spectrometry (LCMS). Our results confirmed that fecal metabolite patterns differ between feline species. The identity of PGFM was confirmed in six of eight felids. In Iberian lynx and the Sumatran tiger, PGFM did not exceed 5% of all immunoreactivities. The total number of immunoreactivities varied between two (e.g., domestic cat) and four (e.g., oncilla). Several prostaglandins were identified by LCMS; apart from PGFM, all LCMS-identified prostaglandins, including tetranor-PGFM, did not show any cross-reactivity with our PGFM-specific antibody. This indicates the existence of still unknown eicosanoids and further studies are needed to clarify the origin of the different metabolites. Although differing stages of pregnancy did not reveal significant differences in the composition of metabolites, we could not exclude the possibility that metabolites from other prostaglandins (e.g. PGE2) contributed to the fecal metabolite patterns.