Methodology for profiling the steroid metabolome in animal tissues using ultraperformance liquid chromatography-electrospray-time-of-flight mass spectrometry.

The advent of mass spectrometry-based metabolite profiling techniques should allow investigations into the behavior and regulation of many of the low abundant signaling molecules present in the animal metabolome such as hormones and so aid investigations into the mechanisms of endocrine system function and disorders. Examples of their potential applications include endocrine-related diseases such as some cancers, as well as endocrine disruption in wildlife and humans caused by some environmental contaminants. In the present study, a method was developed to profile a variety of vertebrate steroids and their conjugates in fish tissues using solid phase extraction (SPE) prior to ultraperformance liquid chromatography linked to electrospray-time-of-flight mass spectrometry (UPLC-TOF MS). Analysis of tissue extracts spiked with steroids revealed that most analytes could be detected at subnanogram per gram concentrations in liver or testes, but ovarian extracts caused ion suppression of estrogens. A comparison of the steroid metabolome of the ovaries and testes using partial least-squares discrimination analysis (PLS-DA) revealed that the androgens 11-ketotestosterone, 11-hydroxyandrostenedione, androstenedione, and two unidentified cortisol-type glucocorticoids were discriminatory steroid markers in testes extracts. In contrast, cortisol was the predominant glucocorticoid marker in ovary extracts, and cortisone was abundant in extracts of both testes and ovaries. A number of other unidentified nonsteroidal metabolites were also differentially expressed between the testes and ovarian tissues. These studies reveal that metabolite profiling using UPLC-TOF MS is a promising approach to investigate steroid homeostasis in animal tissues.