Simultaneous Determination of the Neurotransmitters and Free Amino Acids in Rat Organs by LC-MS Analysis

Free amino acids were kept at constant levels, and their alterations reflect the real state of energy metabolisms in the cells and living body. Neurotransmitters synthesized from certain amino acids fluctuated along with the current neuro-functional viability. Their content levels in each tissue give us substantial information about their state of health and disease in mammals. The determination method of free amino acids without any derivative or labeling reactions and neurotransmitters in the various rat organs was developed using a single column. The levels of free amino acids and neurotransmitters in the organs could be simultaneously and directly obtained within 80 min. Amino acids and neurotransmitters could be separated within 20 min by using an “Intrada Amino Acid” column and identified by LC-TOF MS analysis, and they were quantitatively analyzed by LC-MS/MS. Leucine and isoleucine could be completely separated by column chromatography of the LC-MS analysis. The tissue specific localization of the amino acids and neurotransmitters obtained in this study can be physiologically explained. Additionally, the muscle specific branched-chain amino acids localization was found and the reasons were discussed.