Contribution of local thyroxine monodeiodination to intracellular 3,5, 3'-triiodothyronine in several tissues of hyperthyroid rats at isotopic equilibrium
The local conversion of T4 as a source of intracellular T3 in several organs of both hypothyroid and euthyroid rats has recently been recognized to be an important phenomenon. In the present study the source and quantity of T3 in various peripheral tissues of hyperthyroid rats were investigated. Athyreotic rats received a continuous iv infusion of T4 over a prolonged period in order to attain hyperthyroid conditions. At the same time, the animals also received a continuous iv infusion of (/sup 125/I)T4 and (/sup 131/I)T3 until isotopic equilibrium was achieved. After the animals were bled and perfused, the source and quantity of T3 in various tissue homogenates and subcellular preparations of liver, kidney, and the anterior pituitary gland were analyzed. In spite of the elevated plasma T3 and T4 levels, the concentration of T3 in the cerebral cortex and cerebellum was within the normal range. The contribution of T3 derived from local T4 to T3 conversion (Lc T3(T4)) was rather low in both parts of the brain when compared with values previously determined for euthyroid rats. Whereas previous studies revealed that Lc T3(T4) contributes significantly to the T3 in the pituitary glands of both hypothyroid and euthyroid rats, this was not the case for the hyperthyroid animals; virtually all T3 was derived from plasma. It was found that the T3 in muscle was derived exclusively from plasma. Both the liver and kidney showed high concentrations of T3. Whereas Lc T3(T4) was the main source of T3 in the liver, it contributed only a minor fraction of the total T3 content in the kidney.
- Research Organization:
- Univ. Hospital, Leiden, Netherlands
- OSTI ID:
- 6223538
- Journal Information:
- Endocrinology; (United States), Journal Name: Endocrinology; (United States) Vol. 115:1; ISSN ENDOA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL MATERIALS
BLOOD
BLOOD PLASMA
BODY
BODY FLUIDS
BRAIN
CARBOXYLIC ACIDS
CENTRAL NERVOUS SYSTEM
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DEHALOGENATION
DEIODINATION
DIGESTIVE SYSTEM
DISEASES
DISTRIBUTION
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE DISEASES
ENDOCRINE GLANDS
GLANDS
HORMONES
HYPERTHYROIDISM
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE 131
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KIDNEYS
LIVER
MAMMALS
MATERIALS
MUSCLES
NERVOUS SYSTEM
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANS
PEPTIDE HORMONES
PITUITARY GLAND
RADIOISOTOPES
RATS
RODENTS
THYROID
THYROID HORMONES
THYROXINE
TISSUE DISTRIBUTION
TRACER TECHNIQUES
TRIIODOTHYRONINE
VERTEBRATES