Thyroid iodide compartments and their implication in the rat thyroid iodine organification

Journal Article · Sat May 01 04:00:00 EDT 1982 · Endocrinology; (United States)

DOI:https://doi.org/10.1210/endo-110-5-1716· OSTI ID:6816244

Bastiani, P; Simon, C

To estimate the relative participation of transported and intrathyroidally generated iodide (internal iodide) in the iodination of newly synthesized and preexisting thyroglobulin (Tg) in the rat thyroid, the specific radioactivities (SRAs) of thyroid iodide, Tg, lysosomal iodine, and plasma hormones were followed for 92 h after radioactive iodide injection in intact or hypophysectomized rats. In control rats, the SRA of Tg and lysosomal iodine reached a maximum at 12 h. However, the SRA of lysosomal iodide was always smaller than that of Tg. In contrast, the SRA of hormonal iodide attained a maximum at 48 h. Thus, newly labeled iodine is endocytosed and mixed inside the lysosomes with older previously iodinated molecules; hormone secretion is mainly due to old labeled iodine (i.e. iodine with a high SRA from 48-96 h). These results are consistent with the presence of least two Tg compartments, with different turnover rates and hormone contents. On the other hand, in hypophysectomized rats, the SRA of Tg, lysosomes, and hormones showed only one maximum, at 24 h. Furthermore, the SRAs of Tg and lysosomes were similar at each time interval. It is inferred that in such rats, the old labeled iodine compartment is strongly reduced, and that inside the lysosomes, newly labeled iodine is predominant. Since in hypophysectomized rats, the recycling of iodide is abolished, it is concluded that in normal rats: 1) transported iodide is organified mainly by direct iodination of newly synthesized Tg, independently of TSH, and 2) internal iodide is organified mainly by delayed iodination of preexisting Tg, this process being TSH dependent.

• Research Organization: Laboratoire d'Endocrinologie Cellulaire, Universite de Provence Centre St. Charles, Marseille
• OSTI ID: 6816244
• Journal Information: Endocrinology; (United States), Journal Name: Endocrinology; (United States) Vol. 110:5; ISSN ENDOA
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BIOCHEMICAL REACTION KINETICS
BODY
CELL CONSTITUENTS
ENDOCRINE GLANDS
GLANDS
GLOBULINS
HORMONES
HYPOPHYSECTOMY
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LYSOSOMES
MAMMALS
MEDICINE
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
PEPTIDE HORMONES
PHYSIOLOGY
PITUITARY HORMONES
PROTEINS
RATS
REACTION KINETICS
RODENTS
SURGERY
THYROGLOBULIN
THYROID
THYROID HORMONES
TSH
VERTEBRATES