Ion-trap mass spectrometry for determination of 3,5,3'-triiodo-L-thyronine and 3,5,3',5'-tetraiodo-L-thyronine in neonatal rat cardiomyocytes.

Our short report describes a method employing electrospray ion-trap mass spectrometry (MS) connected to a reversed phase (C(8)) HPLC system for monitoring of 3,5,3'-triiodo-L-thyronine (T3) and its precursor 3,5,3',5'-tetraiodo-L-thyronine (T4) in neonatal rat cardiomyocytes. The experimental protocol allows simultaneous analysis of the free thyroid hormones in nanomolar concentration range and enables observation of their distribution in cultivation medium over time. The method is a useful tool for MS(2) identification of T3/T4 and analysis of their uptake into mammalian cells.