Objectives: 3-iodothyronamine (T1AM) is an endogenous relative of thyroid hormone which interacts with plasma membrane receptors known as trace amine-associated receptors, and produces functional effects like hypothermia and reduced cardiac contractility. In principle T1AM can be produced from thyroxine by enzymatic decarboxylation and deiodination, but its catabolism is unknown. The present study aimed at determining the catabolism and uptake of exogenous T1AM in rat heart. Methods: Isolated working rat hearts were perfused with T1AM (50 nM) and analysis was performed in the recirculating buffer and in cardiac homogenate. Similar experiments were performed in isolated cardiomyoblasts (H9C2 cells). In the latter model both incubation medium and cell lysate were collected at different times and submitted to analysis. The analytical method included reverse phase HPLC coupled to tandem mass spectrometry (ESI-MS-MS), and unabled contemporary detection of T1AM, 3-iodothyroacetic acid (TA1), thyronamine (T0AM) and thyroacetic acid (TA0). Experimentswere repeated in the presence 0.1 mM iproniazide, an inhibitor of monoamine oxidasesand semicarbazide-sensitive amine oxidases. Results: In both models T1AM concentration in the perfusion buffer decreased exponentially over time (the half life was on the order of 20 min in isolated heart perfused with 200 ml of recirculating buffer). T1AM could be detected in cardiac homogenate and in cell lysate, showing that significant uptake occured. We also detected TA1, a product of T1AM oxidative deamination, which significantly accumulated in cell lysate and cardiac homogenate. Pretreatment of H9C2 cells or isolated hearts with iproniazide significantly inhibited T1AM conversion to TA1. Deiodinated derivatives (i.e. T0AM and TA0) were notdetected in any model. Conclusions: We conclude that T1AM is taken up by cardiomyocytes and can be catabolized to TA1 through iproniazide-sensitive amine oxidases. HPLC-ESI-MS-MS proved to be an effective and quantitative technique to elucidate T1AM metabolism.
Cardiac metabolism of 3-iodothyronamine
CHIELLINI, GRAZIA;SABA, ALESSANDRO;GHELARDONI, SANDRA;ZUCCHI, RICCARDO
2009-01-01
Abstract
Objectives: 3-iodothyronamine (T1AM) is an endogenous relative of thyroid hormone which interacts with plasma membrane receptors known as trace amine-associated receptors, and produces functional effects like hypothermia and reduced cardiac contractility. In principle T1AM can be produced from thyroxine by enzymatic decarboxylation and deiodination, but its catabolism is unknown. The present study aimed at determining the catabolism and uptake of exogenous T1AM in rat heart. Methods: Isolated working rat hearts were perfused with T1AM (50 nM) and analysis was performed in the recirculating buffer and in cardiac homogenate. Similar experiments were performed in isolated cardiomyoblasts (H9C2 cells). In the latter model both incubation medium and cell lysate were collected at different times and submitted to analysis. The analytical method included reverse phase HPLC coupled to tandem mass spectrometry (ESI-MS-MS), and unabled contemporary detection of T1AM, 3-iodothyroacetic acid (TA1), thyronamine (T0AM) and thyroacetic acid (TA0). Experimentswere repeated in the presence 0.1 mM iproniazide, an inhibitor of monoamine oxidasesand semicarbazide-sensitive amine oxidases. Results: In both models T1AM concentration in the perfusion buffer decreased exponentially over time (the half life was on the order of 20 min in isolated heart perfused with 200 ml of recirculating buffer). T1AM could be detected in cardiac homogenate and in cell lysate, showing that significant uptake occured. We also detected TA1, a product of T1AM oxidative deamination, which significantly accumulated in cell lysate and cardiac homogenate. Pretreatment of H9C2 cells or isolated hearts with iproniazide significantly inhibited T1AM conversion to TA1. Deiodinated derivatives (i.e. T0AM and TA0) were notdetected in any model. Conclusions: We conclude that T1AM is taken up by cardiomyocytes and can be catabolized to TA1 through iproniazide-sensitive amine oxidases. HPLC-ESI-MS-MS proved to be an effective and quantitative technique to elucidate T1AM metabolism.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
