Horm Metab Res 1990; 22(6): 329-333
DOI: 10.1055/s-2007-1004913
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© Georg Thieme Verlag, Stuttgart · New York

Influence of Chronic Treatment with Iopanoic Acid on Thyroxine Metabolism in the Newborn Rat

M. Redjem, M. Verdaguer, E. Vigouroux
  • Université des Sciences et Techniques du Languedoc, Laboratoire de Physiologie Comparée II, UA 1197 du CNRS, Montpellier, France
Further Information

Publication History

1988

1989

Publication Date:
14 March 2008 (online)

Summary

Parameters of the peripheral metabolism of thyroxine (T4) were studied in the early postnatal period. Iopanoic acid (IOP) was administered to newborn rats that were either euthyroid or rendered hypothyroid in utero by propylthiouracil (PTU) or methimazole (MMI) administration to the mothers during gestation and injected with thyroxine on postnatal days 6 and 7.

In euthyroid newborn rats given IOP from postnatal day 6, the plasma T4 level increased (+ 50%) while the plasma 3,3',5'-triiodothyronine (T3) level slightly decreased (- 18%). Peripheral deiodination of T4 was also reduced (about - 50%) as estimated by thyroid 125I uptake after injection of 125I (3'-5')L-T4.

In the newborn rats rendered hypothyroid in utero and given T4 on postnatal days 6 and 7, IOP treatment started on day 4 decreased the constant rate of elimination (- 50%), the distribution volume (- 43%) and the metabolic clearance (- 74%) of plasma T4. The results were the same in PTU- and MMI-treated newborn rats.

The differences between newborn and adult animals under IOP treatment are discussed.