Simultaneous determination of pregnenolone sulphate, dehydroepiandrosterone and allopregnanolone in rat brain areas by liquid chromatography-electrospray tandem mass spectrometry

Neurosteroids (NSs) are well known modulators of neuronal activity and by binding to different neuronal receptors are responsible for a broad spectrum of biological and pathophysiological conditions. Here, a sensitive liquid chromatographic-electrospray ionization-tandem mass spectrometric method (LC-ESI-MS/MS) has been developed and validated for the simultaneous determination in rat brain areas of three NSs, i.e. pregnenolone sulphate (PS), dehydroepiandrosterone (DHEA) and allopregnanolone (AP). NSs were extracted with methanol-formic acid, purified by Hybrid-SPE cartridges and subjected to LC-ESI-MS/MS without any preliminary derivatization or deconjugation procedure. Quantitation was performed by multiple reaction monitoring mode with the internal standard method, using deuterium-labelled analogues of the analyzed NSs. The proposed method provided for the first time a direct quantitative determination of PS without hydrolysis; in particular, PS concentrations were found significantly (p<0.01) higher in hippocampus, the brain area associated primarily with memory, than in cortical tissue of control rats, suggesting the important role of this NS in the process of memory formation. The developed method could be successfully applied to quantify simultaneously PS, DHEA and AP levels in brain tissue in order to study their changes during various neurodegenerative diseases and to investigate the role of PS in the brain.