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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
6
|
| pubmed:dateCreated |
1988-1-13
|
| pubmed:abstractText |
Since in skeletal muscle circulating L-T3 is the only source for the hormone bound to nuclei, we investigated the intracellular and intranuclear transport of L-T3 in L6E9 rat skeletal muscle cells. The characteristics of this process were assessed by analyzing the nuclear bound L-T3 as a marker of the internalized hormone and by determining the initial rate of L-T3 uptake. [125I]L-T3 cellular uptake at 37 C reached a plateau at 2 h when the nuclear uptake, after an initial lag phase, was still increasing and represented 4.7% of the cellular uptake. Incubation at 4 C caused [125I]L-T3 cellular uptake to decrease by 77% and nuclear uptake to be abolished. A similar effect on [125I]L-T3 nuclear uptake was obtained after myoblasts were incubated at 37 C with a 1000-fold excess of unlabeled L-T3. The addition of various inhibitors of ATP production, cytoskeleton integrity, endocytosis, and Na+, K+-ATPase that did not interfere with [125I]L-T3 binding to the cell surface or to isolated nuclei caused a dose-dependent reduction of both extranuclear and nuclear uptake, ranging from 34-85%. Scatchard analysis revealed the presence on the myoblast surface of L-T3 high affinity (Ka = 1.6 X 10(9) M-1) and low affinity (Ka = 5.4 X 10(6) M-1) binding sites; other iodothyronines exhibited lower affinity for both sites. Kinetic analysis of L-T3 transport after 60-sec incubation at 23 C defined a process with a Km of 17 +/- 5.6 nM and a maximum velocity of 83 +/- 35 pmol/mg DNA. These results indicate the existence in rat myoblasts of a temperature-dependent, energy-requiring, saturable, and stereospecific L-T3 uptake mechanism, probably mediated through an endocytotic pathway, located on the myoblast plasma membrane, that may regulate L-T3 action in skeletal muscle.
|
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
AIM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Dec
|
| pubmed:issn |
0013-7227
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
121
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
2145-52
|
| pubmed:dateRevised |
2003-11-14
|
| pubmed:meshHeading |
pubmed-meshheading:3678143-Animals,
pubmed-meshheading:3678143-Biological Transport,
pubmed-meshheading:3678143-Cell Line,
pubmed-meshheading:3678143-Cell Nucleus,
pubmed-meshheading:3678143-Kinetics,
pubmed-meshheading:3678143-Muscles,
pubmed-meshheading:3678143-Rats,
pubmed-meshheading:3678143-Receptors, Thyroid Hormone,
pubmed-meshheading:3678143-Subcellular Fractions,
pubmed-meshheading:3678143-Triiodothyronine
|
| pubmed:year |
1987
|
| pubmed:articleTitle |
Intracellular transport of 3,5,3'-triiodo-L-thyronine in rat skeletal myoblasts.
|
| pubmed:affiliation |
Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
|
| pubmed:publicationType |
Journal Article
|