Multicompartmental model for iodide, thyroxine, and triiodothyronine metabolism in normal and spontaneously hyperthyroid cats

Journal Article · Wed Jun 01 00:00:00 EDT 1988 · Endocrinology; (United States)

DOI:https://doi.org/10.1210/endo-122-6-2444· OSTI ID:6974259

Hays, M T; Broome, M R; Turrel, J M

A comprehensive multicompartmental kinetic model was developed to account for the distribution and metabolism of simultaneously injected radioactive iodide (iodide*), T3 (T3*), and T4 (T4*) in six normal and seven spontaneously hyperthyroid cats. Data from plasma samples (analyzed by HPLC), urine, feces, and thyroid accumulation were incorporated into the model. The submodels for iodide*, T3*, and T4* all included both a fast and a slow exchange compartment connecting with the plasma compartment. The best-fit iodide* model also included a delay compartment, presumed to be pooling of gastrosalivary secretions. This delay was 62% longer in the hyperthyroid cats than in the euthyroid cats. Unexpectedly, all of the exchange parameters for both T4 and T3 were significantly slowed in hyperthyroidism, possibly because the hyperthyroid cats were older. None of the plasma equivalent volumes of the exchange compartments of iodide*, T3*, or T4* was significantly different in the hyperthyroid cats, although the plasma equivalent volume of the fast T4 exchange compartments were reduced. Secretion of recycled T4* from the thyroid into the plasma T4* compartment was essential to model fit, but its quantity could not be uniquely identified in the absence of multiple thyroid data points. Thyroid secretion of T3* was not detectable. Comparing the fast and slow compartments, there was a shift of T4* deiodination into the fast exchange compartment in hyperthyroidism. Total body mean residence times (MRTs) of iodide* and T3* were not affected by hyperthyroidism, but mean T4* MRT was decreased 23%. Total fractional T4 to T3 conversion was unchanged in hyperthyroidism, although the amount of T3 produced by this route was increased nearly 5-fold because of higher concentrations of donor stable T4.

• Research Organization: Veterans Administration Medical Center, Palo Alto, CA (USA)
• OSTI ID: 6974259
• Journal Information: Endocrinology; (United States), Vol. 122:6
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
HYPERTHYROIDISM
PATHOGENESIS
THYROXINE
METABOLISM
TRIIODOTHYRONINE
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MODELS
BIOLOGICAL PATHWAYS
CATS
FECES
IODIDES
IODINE ISOTOPES
LIQUID COLUMN CHROMATOGRAPHY
THYROID
TRACER TECHNIQUES
AMINO ACIDS
ANIMALS
BIOLOGICAL MATERIALS
BIOLOGICAL WASTES
BODY
CARBOXYLIC ACIDS
CHROMATOGRAPHY
DISEASES
ENDOCRINE DISEASES
ENDOCRINE GLANDS
GLANDS
HALIDES
HALOGEN COMPOUNDS
HORMONES
IODINE COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MATERIALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANS
PEPTIDE HORMONES
REACTION KINETICS
SEPARATION PROCESSES
THYROID HORMONES
VERTEBRATES
WASTES
550501* - Metabolism- Tracer Techniques
550901 - Pathology- Tracer Techniques