Objectives: 3,5-diiodothyronine (T2) and 3-iodothyronamine (T1AM) are thyroid hormone derivatives which have been shown to produce significant biological effects. Some of these effects appear to involve the interaction with specific intracellular targets. In the present work we investigated whether T2 and T1AM are taken up by hepatocytes. A comparison with the cellular uptake of thyroxine (T4), 3,5,3’-triiodothyronine (T3) and 3-monoiodothyronine (T1) was also performed. Methods: Human hepatocellular carcinoma cells (HepG2) were exposed to exogenous T4, T3, T2, T1, or T1AM (1microM each) for 120 min, then the above mentioned substances were assayed in the incubation medium and in cell lysate by HPLC coupled to tandem mass spectrometry. In other experiments, isolated rat liver was perfused with 50nM T4, T3, T2, and T1AM and tissue concentration was determined after 60 min. Results: Table 1 reports overall recovery, medium concentration, and lysate concentration in HepG2 cells (mean±SEM of 3 experiments, except for T1 which was used in a single experiment). T4 T3 T2 T1 T1AM Recovery % 79± 7 79± 13 98± 8 98 58 ±14 Medium (nM) 413 ±91 651± 73 977± 80 933 489± 121 Lysate (nM) 6860 ±2744 2700 ±1189 510± 74 1333 1740± 577 In the case of T1AM, the experiments were repeated in the presence of the amine oxidase inhibitor iproniazide, and under these conditions recovery averaged 99%, while medium concentration and lysate concentration averaged 681 nM and 7240 nM, respectively. Perfused liver experiments confirmed tissue up-take of T4, T3, T2, or T1AM, whose concentrations averaged 1513, 853, 419, and 113 pmol/g, respectively. Conclusions: Both T1AM and T2 enter hepatocytes and are accumulate in intact liver. T1AM catabolism in quicker than iodothyronine catabolism, and is largerly due to oxidative deamination.
Up-take of thyronines and 3-iodothyronamine in liver cells
GHELARDONI, SANDRA;CHIELLINI, GRAZIA;SABA, ALESSANDRO;ZUCCHI, RICCARDO
2012-01-01
Abstract
Objectives: 3,5-diiodothyronine (T2) and 3-iodothyronamine (T1AM) are thyroid hormone derivatives which have been shown to produce significant biological effects. Some of these effects appear to involve the interaction with specific intracellular targets. In the present work we investigated whether T2 and T1AM are taken up by hepatocytes. A comparison with the cellular uptake of thyroxine (T4), 3,5,3’-triiodothyronine (T3) and 3-monoiodothyronine (T1) was also performed. Methods: Human hepatocellular carcinoma cells (HepG2) were exposed to exogenous T4, T3, T2, T1, or T1AM (1microM each) for 120 min, then the above mentioned substances were assayed in the incubation medium and in cell lysate by HPLC coupled to tandem mass spectrometry. In other experiments, isolated rat liver was perfused with 50nM T4, T3, T2, and T1AM and tissue concentration was determined after 60 min. Results: Table 1 reports overall recovery, medium concentration, and lysate concentration in HepG2 cells (mean±SEM of 3 experiments, except for T1 which was used in a single experiment). T4 T3 T2 T1 T1AM Recovery % 79± 7 79± 13 98± 8 98 58 ±14 Medium (nM) 413 ±91 651± 73 977± 80 933 489± 121 Lysate (nM) 6860 ±2744 2700 ±1189 510± 74 1333 1740± 577 In the case of T1AM, the experiments were repeated in the presence of the amine oxidase inhibitor iproniazide, and under these conditions recovery averaged 99%, while medium concentration and lysate concentration averaged 681 nM and 7240 nM, respectively. Perfused liver experiments confirmed tissue up-take of T4, T3, T2, or T1AM, whose concentrations averaged 1513, 853, 419, and 113 pmol/g, respectively. Conclusions: Both T1AM and T2 enter hepatocytes and are accumulate in intact liver. T1AM catabolism in quicker than iodothyronine catabolism, and is largerly due to oxidative deamination.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
