Metabolism of prostaglandin F2alpha in Eurasian lynx (Lynx lynx) and Asian leopard cat (Prionailurus bengalensis euptilura)
Methods for monitoring endocrine status are useful tools for reproduction management. In particular, successful captive breeding of endangered feline species requires reliable methods for pregnancy diagnosis. In many species, uterine and placental prostaglandin-F2α (PGF2α) is involved in the regulation of reproductive processes. PGF2α is metabolized to 13,14-dihydro-15-keto-PGF2a (PGFM) during the first passage through the lungs. Immunoreactive PGFM is elevated in pregnant felids during the last trimester and is used for pregnancy diagnosis, although authentic PGFM is excreted in negligible amounts. To investigate the metabolism of PGF2α, a radiometabolism study was performed in two individuals of two feline species, Eurasian lynx and leopard cats, by injection of tritiated PGF2α and collection of faecal and urinary samples. All samples were extracted and subjected to HPLC separation. Radioactivity and immunoreactivity towards PGFM were determined in each HPLC fraction. The radio- and immunogramms differ slightly between the two species, and radiolabelled PGFM was present only in minor amounts. One major eicosanoid metabolite was found in all urine and faecal samples analysed, and also in previous studies in faecal samples of several pregnant feline species. Its polarity was similar, but not identical to PGF2α. We hypothesized that PGF2α is metabolized to more polar dinor and tetranor metabolites. First mass spectrometric analyses favoured a dinor metabolite as major compound of PGF2α metabolism in felids. Following identification and validation in the studied species, we aim to use these metabolites to improve pregnancy detection in other felids and probably other carnivores.