Comparison of type I 5′-deiodination of thyroxine and of reverse-triiodothyronine in rat and chicken liver homogenates

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Abstract

The characteristics of 5′-deiodination in the chicken liver have been compared to those in the rat. Using 6-n-propyl-2-thiouracil (PTU) at 1 mM in vitro, it was shown that, in accordance with former in vivo studies, only type I 5′-deiodinase exists in the liver of the chicken. When PTU was used in a concentration (10 μM) close to its Ki species differences could be demonstrated as for PTU sensitivity. 5′-Deiodinase in the chicken liver was more susceptible against the inhibitor. The early thiol-independent phase of deiodination was longer in the chicken than in the rat. Reverse-triiodothyronine (r-T3) seemed to be a more suitable substrate for this enzyme in the chicken when compared to either T4 degradation or r-T3 degradation in the rat. It is concluded that major characteristics of 5′-deiodination in the chicken are similar to those in the rat; however, the slight variances observed might explain some species differences found earlier.

Original languageEnglish
Pages (from-to)400-407
Number of pages8
JournalGeneral and Comparative Endocrinology
Volume63
Issue number3
DOIs
Publication statusPublished - 1986

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Reverse Triiodothyronine
triiodothyronine
thyroxine
Thyroxine
Chickens
thiouracil
chickens
Propylthiouracil
liver
Liver
rats
iodide peroxidase
interspecific variation
Iodide Peroxidase
degradation
L-thyroxine
enzyme substrates
in vivo studies
thiols
Sulfhydryl Compounds

ASJC Scopus subject areas

  • Endocrinology

Cite this

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title = "Comparison of type I 5′-deiodination of thyroxine and of reverse-triiodothyronine in rat and chicken liver homogenates",
abstract = "The characteristics of 5′-deiodination in the chicken liver have been compared to those in the rat. Using 6-n-propyl-2-thiouracil (PTU) at 1 mM in vitro, it was shown that, in accordance with former in vivo studies, only type I 5′-deiodinase exists in the liver of the chicken. When PTU was used in a concentration (10 μM) close to its Ki species differences could be demonstrated as for PTU sensitivity. 5′-Deiodinase in the chicken liver was more susceptible against the inhibitor. The early thiol-independent phase of deiodination was longer in the chicken than in the rat. Reverse-triiodothyronine (r-T3) seemed to be a more suitable substrate for this enzyme in the chicken when compared to either T4 degradation or r-T3 degradation in the rat. It is concluded that major characteristics of 5′-deiodination in the chicken are similar to those in the rat; however, the slight variances observed might explain some species differences found earlier.",
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T1 - Comparison of type I 5′-deiodination of thyroxine and of reverse-triiodothyronine in rat and chicken liver homogenates

AU - Rudas, P.

PY - 1986

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N2 - The characteristics of 5′-deiodination in the chicken liver have been compared to those in the rat. Using 6-n-propyl-2-thiouracil (PTU) at 1 mM in vitro, it was shown that, in accordance with former in vivo studies, only type I 5′-deiodinase exists in the liver of the chicken. When PTU was used in a concentration (10 μM) close to its Ki species differences could be demonstrated as for PTU sensitivity. 5′-Deiodinase in the chicken liver was more susceptible against the inhibitor. The early thiol-independent phase of deiodination was longer in the chicken than in the rat. Reverse-triiodothyronine (r-T3) seemed to be a more suitable substrate for this enzyme in the chicken when compared to either T4 degradation or r-T3 degradation in the rat. It is concluded that major characteristics of 5′-deiodination in the chicken are similar to those in the rat; however, the slight variances observed might explain some species differences found earlier.

AB - The characteristics of 5′-deiodination in the chicken liver have been compared to those in the rat. Using 6-n-propyl-2-thiouracil (PTU) at 1 mM in vitro, it was shown that, in accordance with former in vivo studies, only type I 5′-deiodinase exists in the liver of the chicken. When PTU was used in a concentration (10 μM) close to its Ki species differences could be demonstrated as for PTU sensitivity. 5′-Deiodinase in the chicken liver was more susceptible against the inhibitor. The early thiol-independent phase of deiodination was longer in the chicken than in the rat. Reverse-triiodothyronine (r-T3) seemed to be a more suitable substrate for this enzyme in the chicken when compared to either T4 degradation or r-T3 degradation in the rat. It is concluded that major characteristics of 5′-deiodination in the chicken are similar to those in the rat; however, the slight variances observed might explain some species differences found earlier.

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