LC-MS Quantification of Thyroid Hormones, Their Metabolites, Amino Acids and Neurotransmitters in Liver Tissue

ABSTRACT

Thyroid hormones are involved in the regulation of various biological processes: growth and development, carbohydrate metabolism, oxygen consumption, protein synthesis and fetal development. The actions of thyroid hormones affect the levels of wide range of different enzymes (mainly oxidoreductases) that are involved in the metabolism in liver, heart, and brain. These enzymes influence metabolic reactions involving carbohydrates, steroids, lipids and vital signaling proteins. Moreover, there is sufficient information in the literature about non-genomic action of thyroid hormones.

Apart from the thyroid hormones T4 and T3 other iodothyronine metabolites also exhibit influence over the metabolisms of the tissues. Reverse T3, similarly to T4 has an inhibiting effect over the deiodinase involved in the synthesis of T3. Diiodothyronines have been reported to influence the activity of different enzymes: oxidative in the mitochondria, deiodinase in the pituitary glands, and glucose 6-phosphate dehydrogenase in the liver.

We have developed an analytical method for simultaneous quantification of thyroid hormones, their metabolites, amino acids and organic acids present in rat liver. The analysis is carried out with the aid of a liquid chromatograph with an ion-trap mass detector. Two main emphasizes in our work were sample preparation and the choice of internal standard. This was inevitable, due to the fact that our goal was to conduct a high-throughput analysis of the small metabolites and the relatively high- molecular thyroid hormones.

Keywords:

• LC-MS
• metabolites
• Thyroid hormones