Metabolism of thyroxine in Rana catesbeiana tadpoles during metamorphic climax
Previous studies have indicated that premetamorphic tadpoles do not convert T4 to T3 to a measurable extent (1). The present study was performed to determine whether a T4 5'-monodeiodinating system is acquired at later stages of development. (/sup 125/I)T4 metabolism in vivo was determined in tadpoles at most stages of prometamorphosis and metamorphic climax and, for comparison, in premetamorphic tadpoles. The conversion of (/sup 125/I)T4 to (/sup 125/I)T3, as indicated by the presence of an /sup 125/I-labeled product in serum and liver preparations that cochromatographed with carrier T3, was sometimes observed in tadpoles near the end of prometamorphosis and was always evident in tadpoles that were either undergoing or had completed metamorphic climax. However, during this phase, no correlation could be drawn between the extent of T3 production and morphological development. The formation of T3 from T4 in vivo was significantly decreased in tadpoles pretreated with propylthiouracil. The T45'-monodeiodinating system could be induced in premetamorphic tadpoles by injecting them with either T4 or T3. This finding together with the observation that normal acquisition of this system occurs at the time when endogenous T4 and T3 levels are rising rapidly suggest that its development is under the control of the thyroid hormones.
- Research Organization:
- Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire
- OSTI ID:
- 5478362
- Journal Information:
- Endocrinology; (United States), Vol. 109:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
LABELLED COMPOUNDS
METABOLISM
METAMORPHOSIS
PHYSIOLOGY
THYROXINE
BLOOD SERUM
FROGS
IODINE 125
LARVAE
LIVER
MORPHOLOGY
AMINO ACIDS
AMPHIBIANS
ANIMALS
AQUATIC ORGANISMS
BETA DECAY RADIOISOTOPES
BODY
CARBOXYLIC ACIDS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
GLANDS
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANS
PEPTIDE HORMONES
RADIOISOTOPES
THYROID HORMONES
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques
550201 - Biochemistry- Tracer Techniques