title: Identification and measurement of testosterone in plasma and follicular fluid of the mare, using gas chromatography-mass spectrometry associated with isotope dilution.
abstract: Testosterone has been identified by mass spectrometry in blood and follicular fluid aspirated from mature Graafian follicles of mares. Quantitative measurements made by gas chromatography-mass spectrometry have validated the determination of plasma testosterone made by radioimmunoassay. However, because of high levels of epitestosterone (17 alpha-hydroxyandrost-4-en-3-one) in the follicular fluid, radioimmunoassay overestimates the true concentrations of testosterone. The occurrence of testosterone in mare follicular fluid at a concentration which is two orders of magnitude higher than that in peripheral plasma suggests that the follicle may contribute to the production of circulating testosterone. A biosynthetic pathway for oestradiol-17 beta which involves testosterone is therefore likely to occur in the mare ovary as in many other mammalian species.
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000378:metabolism*; D004845:Epitestosterone / Q000097:blood; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006736:Horses / Q000378:metabolism*; D006080:Ovarian Follicle / Q000378:metabolism*; D013739:Testosterone / Q000097:blood / Q000378:metabolism*
chemical_list: D013739:Testosterone; D004845:Epitestosterone