Expanded LC–MS/MS Method Enables Comprehensive Steroid Profiling During Tadpole Metamorphosis

A team of researchers from the University of Cincinnati (Ohio), the University of Illinois at Urbana–Champaign, and the Salk Institute for Biological Studies (La Jolla, California) developed an expanded liquid chromatography–tandem mass spectrometry (LC–MS/MS) method to quantify 18 steroids. These included primary corticosteroid and sex steroid hormones, as well as corticosteroid synthesis intermediates. The method was applied to measure steroid levels in plasma and tail tissue during natural metamorphosis in tadpoles transitioning to frogs. A paper based on their work was published in General and Comparative Endocrinology (1).

The measurement of adrenal steroids in amphibians is central to many studies. The impact of a variety of environmental stressors, including increased salinity, predators, disease, endocrine-disruption, and global climate change, can be measured through the evaluation of steroids (2-10). Furthermore, frog metamorphosis has been studied in the investigation of corticosteroid hormone signaling during vertebrate development because of conservation of hormone/receptor signaling mechanisms and physiological functions (11-14). “Comprehensive quantification of steroid hormones and their precursors in frogs,” the authors of the paper wrote, “will provide fundamental endocrine understanding for how corticosteroid signaling affects growth, development, physiology, morphology, and behavior in ecological and evolutionary contexts. (1).

Using their LC-MS/MS method, the researchers quantified 13 corticosteroid hormones and intermediates and 5 sex steroids in plasma and tail during natural metamorphosis and in pro-opiomelanocortin. Four of these steroids were consistently quantified in plasma and tail during development of wild-type tadpoles, namely 11-deoxycorticosterone (11-DOC), corticosterone (CORT), aldosterone (ALDO), and 11-dehydrocorticosterone (11-dehydroCORT). Plasma steroid levels increased 4- to 5-fold during metamorphosis, while tail steroids were elevated during premetamorphosis and climax but declined during prometamorphosis (1).

Although LC-MS/MS can provide measurements of all steroids from a single sample, the researchers admit that it is a challenging technique that requires careful attention to quality control and method validation. While antibody-based assays measure one steroid at a time, they are less expensive and can be done in typical laboratory settings. “Most researchers are interested in CORT and/or ALDO rather than all possible intermediates,” the authors wrote. “Past and future studies using antibody-based methods to measure CORT and ALDO will benefit from our results because we identified a limited number of steroids that need to be considered when establishing antibody specificity.’ (1).

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References

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