Simultaneous Measurement of Sex Steroid Hormones in Largemouth Bass (Micropterus salmoides) Plasma by Application of Liquid Chromatography-Tandem Mass Spectrometry

Abstract

Sex steroid hormones are potential biomarkers of reproductive function in teleost fish, but their measurement continues to rely on antibody-based assays. The objective of this study was to optimize a robust and simultaneous liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for measurement of eight steroid hormones (cortisol, 11-ketotestosterone, estradiol, 17α-ethynyl estradiol, estrone, estriol, progesterone and testosterone) in fish plasma. The extraction was followed by liquid-liquid extraction with tert-butyl methyl ether and time scheduled multi-reaction monitoring (sMRM) was used for quantitation of steroids. Validation of method performance using charcoal-stripped human plasma showed extraction recoveries for eight steroids ranged from 85.5 to 108.2% with matrix effects > 80%. The limits of quantitation were 0.01 pg/μL for testosterone, 0.05 pg/μL for cortisol and progesterone, 0.1 pg/μL for 11-ketotestosterone, estradiol and estrone, 0.125 pg/μL for estriol and 0.25 pg/μL for 17α-ethynyl estradiol. The proposed method was applied to plasma samples of largemouth bass (Micropterus salmoides) collected from contaminated (Lake Apopka) and reference sites (Wildcate Lake) in Florida. Concentrations of testosterone, cortisol, estradiol and estrone were significantly different in female fish, but plasma concentration of cortisol was only statistically different in male fish between two sites (P < 0.05). This study demonstrates the application of a robust LC-MS/MS analysis for a range of sex steroid hormones representative of endocrine function in a top predator, largemouth bass.