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Kinetics of thyroxine (T4) and triiodothyronine (T3) transport in the isolated rat heart

Published online by Cambridge University Press:  31 July 2001

Mirko A. Rosic ,
Suzana B. Pantovic ,
Aleksandra P. Lucic ,
Nevena Ribarac-Stepic  and
Ivan Z. Andjelkovic
Mirko A. Rosic
Affiliation:
Institute of Physiology, Faculty of Medicine, University of Kragujevac, Kragujevac, Institute of Nuclear Science 'Vinca', Belgrade and Institute of Physiology, Faculty of Medicine, University of Belgrade,Yugoslavia
Suzana B. Pantovic
Affiliation:
Institute of Physiology, Faculty of Medicine, University of Kragujevac, Kragujevac, Institute of Nuclear Science 'Vinca', Belgrade and Institute of Physiology, Faculty of Medicine, University of Belgrade,Yugoslavia
Aleksandra P. Lucic
Affiliation:
Institute of Physiology, Faculty of Medicine, University of Kragujevac, Kragujevac, Institute of Nuclear Science 'Vinca', Belgrade and Institute of Physiology, Faculty of Medicine, University of Belgrade,Yugoslavia
Nevena Ribarac-Stepic
Affiliation:
Institute of Physiology, Faculty of Medicine, University of Kragujevac, Kragujevac, Institute of Nuclear Science 'Vinca', Belgrade and Institute of Physiology, Faculty of Medicine, University of Belgrade,Yugoslavia
Ivan Z. Andjelkovic
Affiliation:
Institute of Physiology, Faculty of Medicine, University of Kragujevac, Kragujevac, Institute of Nuclear Science 'Vinca', Belgrade and Institute of Physiology, Faculty of Medicine, University of Belgrade,Yugoslavia
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Abstract

The dynamics and kinetics of thyroid hormone transport in the isolated rat heart were examined using the modified unidirectional paired tracer dilution method. The uptake of 125I-thyroxine (125I-T4) and 125I-triiodothyronine (125I-T3) from the extracellular space into heart cells was measured relative to the extracellular space marker 3H-mannitol. The thyroid hormone maximal uptake was 54.4 % for 125I-T4 and 52.15 % for 125I-T3. The thyroid hormone net uptake was 25.69 % for 125I-T4 and 25.49 % for 125I-T3. Backflux from the intracellular space was 53.17 % for 125I-T4 and 61.59 % for 125I-T3. In the presence of unlabelled thyroid hormones, 125I-T4 and 125I-T3 maximal uptakes were reduced from 10.1 to 59.74 % and from 34.6 to 65.3 %, respectively, depending on the concentration of the unlabelled hormone, suggesting a saturable mechanism of the thyroid hormone uptake by the heart cells, with Km(T4)= 105.46 µM and the maximal rate of 125I-thyroid hormone flux from the extracellular space to heart cells (Vmax(T4)) = 177.84 nM min-1 for 125I-T4 uptake, and Km(T3) = 80.0 µM and Vmax(T3) = 118.5 nM min-1 for 125I-T3 uptake. Experimental Physiology (2001) 86.1, 13-18.

Type
Research Article
Information
Experimental Physiology , Volume 86 , Issue 1 , January 2001 , pp. 13 - 18
Copyright
© The Physiological Society 2001

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