Simultaneous monitoring of monoamines, amino acids, nucleotides and neuropeptides by liquid chromatography‐tandem mass spectrometry and its application to neurosecretion in bovine chromaffin cells

The primary functions of adrenal medullary chromaffin cells are the synthesis and storage in their chromaffin vesicles of the catecholamines noradrenaline (NA) and adrenaline (AD), and their subsequent release into the bloodstream by Ca²⁺‐dependent exocytosis under conditions of fear or stress (fight or flight response). Several monoamines, nucleotides and opiates, such as leucine‐enkephalin (LENK) and methionine‐enkephalin (MENK), are also co‐stored and co‐released with the catecholamines. However, other neurotransmitters have not been studied in depth. Here, we present a novel high‐resolution liquid chromatography‐tandem mass spectrometry approach for the simultaneous monitoring of 14 compounds stored and released in bovine chromaffin cells (BCCs). We validated the analytical method according to the recommendations of the EMA and FDA by testing matrix effect, selectivity, sensitivity, precision, accuracy, stability and carry‐over. After testing on six batches of BCCs from different cultures, the method enabled simultaneous quantitative determination of monoamines (AD, NA, dopamine, serotonin, 5‐hydroxyindoleacetic acid, histamine and metanephrine), amino acids (L‐glutamic acid, γ‐aminobutyric acid), nucleotides (adenosine 5′‐diphosphate, adenosine 5′‐monophosphate, cyclic adenosine 5′‐monophosphate) and neuropeptides (LENK and MENK) in the intracellular content, basal secretion and acetylcholine induced secretion of BBCs. The high‐resolution approach used here enabled us to determine the levels of 14 compounds in the same BCC batch in only 16 min. This novel approach will make it possible to study the regulatory mechanisms of Ca²⁺ signaling, exocytosis and endocytosis using different neurotrophic factors and/or secretagogues as stimuli in primary BCC cultures. Our method is actually being applied to human plasma samples of different therapeutic areas where sympathoadrenal axis is involved in stress situations such as Alzheimer's disease, migraine or cirrhosis, to improve diagnosis and clinical practice. Copyright © 2016 John Wiley & Sons, Ltd.