Energy Metabolism in Spermatozoa of Domestic Cats and Cheetahs
2013 SSR Annual Conference (Montreal) - abbreviated abstract
Metabolomic characterization of epididymal spermatozoa and fluid in the domestic cat (Felis catus)
Halli Sigal, Brian J.Bequette, Adrienne Crosier, Carol L Keefer
Following completion of spermatogenesis, spermatozoa migrate from the rete testis into the epididymis where final maturation takes place. Changes in membrane composition and metabolism, as well as acquisition of fertilizing ability and progressive motility also characterize this transit. Once introduced to the female tract, sustained motility, capacitation and the acrosome reaction require high levels of cellular energy in the form of ATP. Previous studies in spermatozoal metabolism have identified glycolysis, oxidative phosphorylation, the Krebs cycle, and β-oxidation as essential energy synthesizing processes in mammalians. However, the specific importance of each pathway is not fully understood in the felid model. Teratospermia is a well-documented phenomenon, occurring in approximately 90% of felids, and is known to impair spermatozoa metabolism. Sperm function is further impaired following cryopreservation and in vitro manipulation. Understanding normal function of felid gamete metabolism is an important goal through which assisted reproductive techniques could be improved. Using the domestic cat as a model for exotic and endangered felid species, our study characterized the metabolic profiles of epididymal fluid (EF) and spermatozoa (ES) using gas-chromatography mass-spectrometry (GCMS). Evaluation of metabolites present in epididymal fractions following GCMS analysis revealed the presence of glycolytic products (e.g. inositol in all seven individuals; glycerol in 6 of 7 individuals; lactic acid in 5 of 7 individuals) in EF and ES fractions. Oxalic acid, an intermediate in the Krebs cycle, was present in all individuals. Succinic, malic, and citric acids (Krebs cycle intermediates) were also present. High peaks indicating stearic, and palmitic acids were present in all 7 individuals, as well as smaller peaks indicating linoleic and arachidonic acids. Cholesterol was also detected among all individuals. Leucine was a key amino acid present among all individuals. This study confirms the analysis of epididymal fluid and sperm by GCMS for metabolite identification and semi-quaintification, thus providing a useful tool to discern metabolic phenotypes associated with altered function of felid gametes in vitro. Our findings will serve as a template for studies on the underlying metabolic processes of sperm from normal and tetratospermic individual felids.