Document Detail

Characteristics of the uptake of 3,5,3'-triiodo-L-thyronine and L-thyroxine into red blood cells of rainbow trout (Oncorhynchus mykiss).
MedLine Citation:
PMID:  8812373     Owner:  NLM     Status:  MEDLINE    
The mechanisms of uptake of thyroid hormones (TH) 3,5,3'-triiodo-L-thyronine (T3) and L-thyroxine (T4) by trout red blood cells (RBC) were characterized by coincubating washed RBC with [125I]T3 or [125I]T4 and a variety of inhibitors and potentially competing amino acids and TH analogues. Nonsaturable uptake of both TH was unaffected by almost all agents tested, consistent with a diffusion process. Saturable T3 uptake was unaffected by a major (80%) cyanide- and iodoacetate-induced reduction in RBC nucleotide triphosphate content or by inhibitors of Na+ transport, but was depressed by (i) inhibitors of protein binding (bromosulfophthalein, 8-anilino-1-naphthalene sulfonic acid, phloretin, and 5,5'-diphenylhydantoin, (ii) sulfhydryl blockers (p-hydroxy-mercuribenzoate and N-ethylmaleimide), (iii) endocytotic inhibitors (chloroquine, colchicine, and monodansylcadaverine), (iv) tryptophan and phenylalanine, and (v) certain TH analogues, particularly 3,3',5'-triiodo-L-thyronine (reverse T3). In contrast, saturable T4 uptake was depressed only by inhibitors or protein binding. Cross-competition between T3 and T4 for transport occurred only at highly pharmacologic TH levels. We conclude that T3 and T4 are transported into trout RBC by two separate systems. The relatively slow T4 uptake depends on binding to certain proteins. The much more rapid T3 uptake depends on protein binding, but is Na(+)-independent, and involves a system comparable to the T-system of aromatic amino acid transport. However, participation od receptor-mediated endocytosis cannot be excluded.
J M McLeese; J G Eales
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  General and comparative endocrinology     Volume:  103     ISSN:  0016-6480     ISO Abbreviation:  Gen. Comp. Endocrinol.     Publication Date:  1996 Aug 
Date Detail:
Created Date:  1996-12-19     Completed Date:  1996-12-19     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370735     Medline TA:  Gen Comp Endocrinol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  200-8     Citation Subset:  IM    
Department of Zoology, University of Manitoba, Canada.
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MeSH Terms
Endocytosis / drug effects
Energy Metabolism
Erythrocytes / metabolism*
Ethylmaleimide / pharmacology
Iodine Radioisotopes
Leucine / pharmacology
Oncorhynchus mykiss / blood*
Phenylalanine / pharmacology
Protein Binding / drug effects
Sodium / pharmacology
Thyroxine / blood*
Triiodothyronine / blood*
Tryptophan / pharmacology
Reg. No./Substance:
0/Iodine Radioisotopes; 128-53-0/Ethylmaleimide; 61-90-5/Leucine; 63-91-2/Phenylalanine; 6893-02-3/Triiodothyronine; 73-22-3/Tryptophan; 7440-23-5/Sodium; 7488-70-2/Thyroxine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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