Spatial Localization and Quantitation of Androgens in Mouse Testis by Mass Spectrometry Imaging

Androgens are essential for male development and reproductivefunction. They are transported to their site of action as blood-borneendocrine hormones but can also be produced within tissues to act inintracrine and paracrine fashions. Because of this, circulating concentrationsmay not accurately reflect the androgenic influence within specific tissuemicroenvironments. Mass spectrometry imaging permits regional analysis ofsmall molecular species directly from tissue surfaces. However, due to poorionization and localized ion suppression, steroid hormones are difficult todetect. Here, derivatization with Girard T reagent was used to charge-tagtestosterone and 5α-dihydrotestosterone allowing direct detection of thesesteroids in mouse testes, in both basal and maximally stimulated states, and inrat prostate. Limits of detection were ∼0.1 pg for testosterone. Exemplarydetection of endogenous steroids was achieved by matrix-assisted laserdesorption ionization and either Fourier transform ion cyclotron resonancedetection (at 150 μm spatial resolution) or quadrupole-time-of-flight detection (at 50 μm spatial resolution). Structuralconfirmation was achieved by collision induced fragmentation following liquid extraction surface analysis and electrosprayionization. This application broadens the scope for derivatization strategies on tissue surfaces to elucidate local endocrinesignaling in health and disease.