3-iodothyronamine (T1AM) is a novel relative of thyroid hormone, able to interact with specific G protein-coupled receptors, known as trace amine-associated receptors. Exogenous T1AM has been shown to produce functionally effects, e.g. reducing body temperature and cardiac contractility. However, a quantitative and comprehensive analysis of T1AM distribution and metabolism has not been performed in any tissue. In the present study we describe a novel liquid chromatography tandem mass spectrometry method that allowed to evaluate endogenous T1AM distribution in different rat tissues and its catabolism in cardiac preparations. In addition, we prepared isotope labelled T1AM (125I-T1AM) which was administered to mice (100 μCi, i.v.) to elucidate T1AM bio-distribution and pharmacokinetics. T1AM was detected in rat serum, at the concentration of 0.3±0.03 pmol/ml and in all tested organs (heart, liver, kidney, skeletal muscle, stomach, lung, and brain), at concentrations which were significantly higher than the serum concentration, ranging from 5.6±1.5 pmol/g in lung, to 36.1±10.4 in kidney and 92.9±28.5 pmol/g in liver. In H9C2 cardiomyocytes and in isolated perfused rat hearts significant uptake of exogenous T1AM was observed, and at the steady state total cellular or tissue T1AM concentration exceeded extracellular concentration by over 20-fold. In both preparations T1AM underwent oxidative deamination to 3-iodothyroacetic acid (TA1) and our data suggest that TA1 production occurred intracellularly and was followed by TA1 release. T1AM deamination was inhibited by iproniazid but not by pargiline or semicarbazide, suggesting the involvement of both monamine oxidase and semicarbazide-sensitive amine oxidase. Our preliminary in vivo biodistribution studies indicated that [125I]-T1AM was predominantly localized in the gastrointestinal tract, kidney and liver. The specificity of [125I]-T1AM uptake was confirmed in blocking studies.Coinjection of unlabeled T1AM (25 microg/kg) reduced the activity of [125I]-T1AM by more than 90%.In conclusion, our results suggest that T1AM is an endogenous compound, which is widely distributed and is a substrateof amine oxidases. The highest T1AM levels are detected in the liver, kidney and gastrointestinal tract.
3-Iodothyronamine as a novel endogenous chemical messenger: tissue distribution and catabolism
CHIELLINI, GRAZIA;SABA, ALESSANDRO;GHELARDONI, SANDRA;ERBA, PAOLA ANNA;ZUCCHI, RICCARDO
2010-01-01
Abstract
3-iodothyronamine (T1AM) is a novel relative of thyroid hormone, able to interact with specific G protein-coupled receptors, known as trace amine-associated receptors. Exogenous T1AM has been shown to produce functionally effects, e.g. reducing body temperature and cardiac contractility. However, a quantitative and comprehensive analysis of T1AM distribution and metabolism has not been performed in any tissue. In the present study we describe a novel liquid chromatography tandem mass spectrometry method that allowed to evaluate endogenous T1AM distribution in different rat tissues and its catabolism in cardiac preparations. In addition, we prepared isotope labelled T1AM (125I-T1AM) which was administered to mice (100 μCi, i.v.) to elucidate T1AM bio-distribution and pharmacokinetics. T1AM was detected in rat serum, at the concentration of 0.3±0.03 pmol/ml and in all tested organs (heart, liver, kidney, skeletal muscle, stomach, lung, and brain), at concentrations which were significantly higher than the serum concentration, ranging from 5.6±1.5 pmol/g in lung, to 36.1±10.4 in kidney and 92.9±28.5 pmol/g in liver. In H9C2 cardiomyocytes and in isolated perfused rat hearts significant uptake of exogenous T1AM was observed, and at the steady state total cellular or tissue T1AM concentration exceeded extracellular concentration by over 20-fold. In both preparations T1AM underwent oxidative deamination to 3-iodothyroacetic acid (TA1) and our data suggest that TA1 production occurred intracellularly and was followed by TA1 release. T1AM deamination was inhibited by iproniazid but not by pargiline or semicarbazide, suggesting the involvement of both monamine oxidase and semicarbazide-sensitive amine oxidase. Our preliminary in vivo biodistribution studies indicated that [125I]-T1AM was predominantly localized in the gastrointestinal tract, kidney and liver. The specificity of [125I]-T1AM uptake was confirmed in blocking studies.Coinjection of unlabeled T1AM (25 microg/kg) reduced the activity of [125I]-T1AM by more than 90%.In conclusion, our results suggest that T1AM is an endogenous compound, which is widely distributed and is a substrateof amine oxidases. The highest T1AM levels are detected in the liver, kidney and gastrointestinal tract.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
