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Endocrinology Research Laboratory, West Los Angeles VA Medical Center, University of California, Los Angeles, California 90073
Address all correspondence and requests for reprints to: Dr. Jerome M. Hershman, West Los Angeles VA Medical Center, Endocrinology 111D, 11301 Wilshire Boulevard, Los Angeles, California 90073. E-mail: jhershman{at}ucla.edu
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Young (<20 passages) and aged (>40 passages) FRTL-5 cells grown with or without TSH were treated with various concentrations of TNF, TGF-ß1, sphingomyelinase, or ceramide. NIS messenger RNA (mRNA) levels in aged cells were only 2% of those in young cells. Withdrawal of TSH from young cells reduced NIS mRNA levels by more than 90%. TNF reduced NIS mRNA levels in young cells grown with TSH at t1/2 = 0.62 days, a cycloheximide inhibitable effect. Similar treatments with TGF-ß1, sphingomyelinase, or ceramide reduced NIS mRNA by 70–90%. Ceramide reduced 125I--uptake by 50%. The addition of TNF increased both the sphingomyelin and ceramide levels 3- to 5-fold in young and old cells.
We conclude that 1) the decline in iodide uptake due to aging, a fall in serum TSH or an increase in TNF or TGF-ß1 is mediated primarily by a reduction in thyroid NIS expression; and 2) that receptor-mediated activation of sphingomyelinase is an important, protein synthesis-dependent, intracellular pathway for inhibition of NIS expression by TNF.
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Withdrawal of TSH, cytokine treatment, or aging have inhibitory effects on this initial step in thyroid hormone synthesis (6, 7, 12, 13, 18, 19, 20, 21, 22, 23, 24). Thyroid follicular cells transport iodide from blood into the follicular lumen against an iodide gradient by means of an inward Na+ gradient maintained by Na+/K+-ATPase and coupled transport of Na+ and I- ions via the Na+/I--symporter (NIS) (25). Expression and activity of Na+/K+-ATPase is also reduced by TSH withdrawal, aging, or tumor necrosis factor (TNF) treatment (10). The last step in thyroid hormone synthesis, conversion of T4 to T3 by type I deiodinase, is also inhibited by these same factors (4, 5). Aging-dependent increase in the sphingomyelin and ceramide content of the plasma membrane and decrease in its phosphatidylcholine content (26) are important components of cellular senescence (27). Reduction in the expression of the TSH (11) and TNF (6) receptors, possibly an adaptive response to altered phospholipid composition and second messenger signaling in the plasma membrane, may contribute to the increased incidence of abnormal regulation of iodide uptake and thyroid hormone metabolism with aging (12).
The mechanisms of signal transduction that follow binding of TNF to its
receptors is a very active area of biomedical research. Two different
receptors, TNF-R1 (55 kDa) and TNF-R2 (75 kDa), mediate the effects of
TNF. Two cytoplasmic regions within TNF-R1 have been identified, the
neutral sphingomyelinase activation domain (NSD) and the death domain,
and they are responsible for activating signaling cascades initiated by
neutral sphingomyelinase and NF-
B, respectively (28). TRADD is a
TNF-R1-associated signal transducer that directly interacts with TRAF2
and FADD, signal transducers that activate NF-B and induce
apoptosis, respectively (29). Activation of NF-B results in
increased expression of a number of cytokines including IL-6 (30, 31).
IL-6 complexed with soluble IL-6 receptor binds to gp130, an IL-6
signal transducer in the plasma membrane of thyroid and other cells,
resulting in reduced iodide uptake and thyroid hormone synthesis by
human thyroid follicles in culture (18). Serum IL-6 levels can increase
50-fold in NTI and serum T3 and T4 levels are
negatively correlated with serum IL-6 levels (19).
Phospholipase A2 (PLA2) has recently been
reported to be an early step in one of the second messenger signaling
systems for TNF, IL-1ß, and IFN-
(26, 32, 33). Activated
PLA2 hydrolyzes phosphatidylcholine, releasing arachidonic
acid. This product, which is a potent mediator of inflammation, then
activates sphingomyelinase, which, in turn, converts sphingomyelin to
ceramide. Phosphatidylcholine
lysophosphatidylcholine + arachidonic
acid Sphingomyelin
ceramide + phosphocholine
TNF, IL-1ß, IFN- and ceramide have recently been
reported (4, 5) to have marked inhibitory effects on the expression and
activity of the type I deiodinase, a selenoenzyme (34), in FRTL-5 rat
thyroid cells. On the other hand, transforming growth factor
(TGF)-ß1, which has potent antiinflammatory and growth
inhibitory effects on epithelial cells (35, 36), does not activate
sphingomyelinase (37) and has no effect on the expression of this
enzyme. Nevertheless, TGF-ß1 potently suppresses
Na+/K+-ATPase expression and activity and
iodide transport in FRTL-5 cells (7, 10).
In the present studies we examine in more detail the mechanisms by which TSH, aging, TNF, and TGF-ß1, which play important roles in the nonthyroid illness syndrome and the age-associated hypothyroidism, regulate the expression of NIS, and thereby the uptake of iodide, by rat thyroid cells in culture.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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(4.03 x 107 U/mg)
and mouse TNF- (5 x 107 U/mg) were a generous gift
of Genentech (South San Francisco, CA). Recombinant human
TGF-ß1 (1 x 106 U/mg) was donated by
Amgen (Thousand Oaks, CA).
N-palmitoyl-D-sphingosine (ceramide),
sphingomyelinase (S. aureus) in 50% glycerol containing
0.25 M phosphate buffer, pH 7.5, platelet factor 4 (PF 4)
and cycloheximide were obtained from Sigma Chemical (St. Louis, MO).
Glycerol, which is toxic to FRTL-5 cells at a final concentration as
low as 0.5%, was removed from sphingomyelinase by dilution in sterile
saline and centrifugal ultrafiltration with Ultrafree-MC filter units,
NMWL: 10,000 (Sigma). Other chemicals, hormones, and reagents were
purchased from Sigma.
Cells
The rat thyroid cells used in the present studies were either
less than 20 passages (young, doubling time 48 h, cuboidal shape)
or more than 40 passages after subcloning (aged, doubling time 36
h, stellate shape). Young FRTL-5 cells were kindly provided by Dr.
Leonard D. Kohn (NIH, Bethesda, MD). The aged FRTL-5 cell line was
developed in our laboratory by repeated passages for more than 3 months
(6). These cells have markedly increased expression of TGF-ß (15), an
important, senescence-associated characteristic of aging cells, both
in vitro and in vivo (20, 38, 39). FRTL-5 cells
were cultured in Coon’s modified Ham’s F-12 medium supplemented with
six hormones (bTSH, 2 U/liter; insulin, 246 U/liter; somatostatin, 10
µg/liter; hydrocortisone, 10 nM; transferrin, 5 mg/liter;
glycyl-histidyl-lysine, 2.5 µg/liter), 5% calf serum and antibiotics
(6H medium), as previously described (13, 14). Cells were maintained in
a 5% CO2-95% air atmosphere at 37 C with a change of
medium every third day and passed every 7 days. Cells to be studied in
TSH-free (5H) medium were rinsed once with sterile saline and the
TSH-free medium was changed 3 days before and on the day of test
substance addition. Three days was the minimum time required for
TSH-stimulated effects on NIS expression to dissipate. FRTL-5 cells
survive for 10 days in TSH-free medium.
RNA extraction and electrophoresis
Total RNA was extracted by a guanidinium thiocyanate method from
cultured cells (40). Quadruplicate aliquots of each sample, 10 µg
RNA/lane, were electrophoresed from tandem wells cast in the end and
middle of two 1% agarose gels containing 1.0% formaldehyde (15).
Following electrophoresis, half of one of the gels was stained with
ethidium bromide. The other half of this gel and the complete tandem
gel were Northern blotted on nitrocellulose (Schleicher & Schuell,
Inc., Keene, NH) by capillary transfer with 10 x SSC and baked
for 1 h at 80 C under vacuum. Following Northern blotting, the
gels were stained with ethidium bromide to verify the quantitative
transfer of RNA onto the nitrocellulose filter.
Hybridization
We used a full-length rat NIS cDNA probe, a gift of Dr. Nancy
Carrasco and Dr. Orlie Levy (Albert Einstein College of Medicine,
Bronx, NY) (1). Filters were prehybridized for 4 h at 65 C in 10
ml of hybridization solution [composed of 1.5 x SSPE (0.15
M NaCl, 0.01 M NaH2PO4,
0.001 M EDTA)/7% SDS/10% PEG (polyethylene glycol mol wt
8000)] and augmented with 100 µg/ml sonicated and heat-denatured
salmon sperm DNA and 250 µg/ml heparin and hybridized overnight at 65
C with hybridization solution containing 50 ng 32P-labeled
cDNA probe (250 µCi/µg). Filters were washed twice for 10 min at
room temperature with wash buffer (0.1 x SSC, 0.1% SDS) and
twice for 10 min at 65 C with wash buffer (41). Relative messenger RNA
(mRNA) ratios were determined by scanning densitometry of the
autoradiograms and normalized by the fluorescence intensities of the
corresponding ethidium bromide-stained 18S and 28S ribosomal RNA
bands.
Blots were also hybridized with 32P-labeled cDNA probes for
rat type I deiodinase (Dr. P. Reed Larsen, Brigham and Women’s
Hospital, Boston, MA), Na+/K+-ATPase - and
ß-subunits (Dr. Jerry Lingrel, University of Cincinnati, Cincinnati,
OH) and TGF-ß isoforms 1, 2, and 3 (Dr. Rik Derynck, University of
California, San Francisco, CA) to establish the specificity of the NIS
mRNA suppression by the various treatments used.
Treatment of cells with ceramide
C16-ceramide is not soluble in aqueous solutions or
ethanol. Recently, a solvent mixture of ethanol and dodecane (98:2
vol/vol) has been reported to fully solubilize C16-ceramide
(42). When diluted in serum-free medium to a final concentration of
ethanol and dodecane of 0.5% and 0.01%, respectively, the
C16-ceramide is readily taken up by cells and incorporated
into sphingomyelin. At the doses used, ethanol and dodecane had no
effect on cell proliferation. Another factor that interferes with
C16-ceramide uptake by cells is its affinity for the
hydrophobic binding site on albumin (43). To minimize this competitive
binding effect, which may greatly diminish or abolish cellular uptake
of this test substance, cell culture medium containing only 0.05% BSA
instead of 5% calf serum was used in all experiments with
C16-ceramide.
125I uptake
FRTL-5 cells were seeded in 24-well plates (0.5 x
105 cells/well). Cells were maintained in standard,
TSH-containing medium and medium was changed every third day. On the
seventh day, the medium was changed and test agents were added. After
48 h, the cells were washed twice with 1 ml of cold HBSS, 25 µl
(12,000–15,000 cpm) Na125I in 10 µM KI were
added to each well and incubated at 37 C for 40 min, then
nontransported 125I was washed off with 1 ml HBSS.
Intracellular Na125I was released by incubating with 25
µl 20 mM KClO4 in 0.5 ml HBSS for an
additional 30 min. The medium of each well was counted for
125I.
DNA content
The total DNA content of each well was measured by the
fluorometric mithramycin-binding method (44). The total DNA per well
was used to normalize the 125I-uptake results.
Cell labeling with 3H-palmitic acid
FRTL-5 cells were grown to near confluency in FRTL-5 medium
containing 2 U/liter bTSH. Cells were washed with sterile saline, and
then fresh medium with various concentrations of TSH (0 to 2 U/liter)
was added with or without 50 ng/ml TNF. After 24 h incubation,
3H-palmitic acid (DuPont-New England Nuclear Research
Products, Boston, MA; 30–60 Ci/mmol, 1 µCi/ml) was added to each
flask. After an additional 48-h incubation, cells were washed with
saline. Fresh, serum-free medium was then added, which had the same TSH
concentration as the original medium but did not contain TNF or tracer.
Three hours later, the cells were washed with homogenization buffer (50
mM NaF, 5 mM EGTA, 25 mM HEPES, pH
7.4) and then homogenized with 2 ml of homogenization buffer using 50
strokes of a tight-fitting Dounce homogenizer. The homogenate was
centrifuged for 5 min at 500 x g.
Lipid extraction and chromatography
Lipids in the supernatant were extracted with 1 ml of
chloroform:methanol: concentrated hydrochloric acid (100:100:1) and 0.3
ml of 0.01 M EDTA in BSS. The glycerophospholipids were
saponified with 0.1 M KOH for 1 h at 37 C. After
drying under nitrogen and redissolving the samples in
chloroform:methanol (1:1), 3H-labeled sphingomyelin was
isolated from the organic phase by TLC (silica gel G, Analtech, Newark,
DE) using chloroform: methanol:acetic acid:H2O
(25:15:4:1.5). Sphingomyelin standards were visualized by iodine vapor
and radioactivity was determined by scraping and counting
3H-labeled fractions (45). 3H-ceramide was
fractionated by silica gel TLC using heptane:ethyl acetate:acetic acid
(80:20:1) with unlabeled sphingomyelin (RF 0.00), and
ceramide (RF 0.133), stained with iodine vapor, and
3H-palmitic acid (RF 0.467) as markers for
scraping and counting 3H-labeled fractions. The nuclear
pellet was saved for DNA measurement by the mithramycin fluorescent dye
binding method (44).
Statistical analysis
Results presented are representative of at least three replicate
experiments. Error bars represent 1SD. When error bars are
not visible, they are obscured by the symbol for the mean. Results were
analyzed by one-way ANOVA using the Scheffé’s post hoc factorial
contrasts.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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, left panels). Addition for
3 days of various doses of TSH, to similarly treated cells, produced a
monotonic increase in NIS mRNA levels to a plateau value, 17-fold (95%
confidence limits: 7.5 and 33) above the baseline, at 222 mU/liter
bovine TSH (Fig. 1, right panels). The mRNA transcript in
cells maintained in TSH-free medium was readily detectable using longer
exposure times of the Northern blot. These results are consistent with
earlier reports on the time and concentration-dependent induction of
NIS mRNA by TSH in vitro and in vivo (21, 24).
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). One-day treatment
with various doses of human TNF reduced NIS mRNA levels in an
approximately linear log dose-response manner (Fig. 2B). NIS mRNA
levels in aged cells grown in TSH-containing medium were low but
readily detectable (2–5% of the corresponding young cell values) and
were not affected by adding TNF to the medium (Fig. 2A). In contrast
with the continuous reduction of NIS mRNA levels in response to human
TNF, as seen in panel A, the NIS mRNA level began to increase after
reaching a nadir of 14% of the control value at 1 day after the start
of treatment with mouse TNF and returned to almost the initial value by
3 days of treatment, as seen in panel C. Two-day treatment with various
doses of mouse TNF up to 100 ng/ml reduced NIS mRNA levels in a
dose-dependent manner to 22% of the untreated control as seen in
panels D and E.
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). Ceramide
(37 µM) reduced NIS mRNA levels by 89% after 24 h
treatment (Fig. 4). No morphologic
changes, loss of cell viability, or alteration in growth rate were
detected in response to these treatments. Two-day treatment with
ceramide (20 µg/ml) also reduced 125I uptake by 50%
(Fig. 5).
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and related blots with a 32P-labeled
rat type I iodothyronine deiodinase (D1) cDNA probe revealed no time-
or dose-dependent effects of ceramide on D1 mRNA levels (16).
Cycloheximide (CHX) blocks TNF suppression of NIS expression and
activity
As shown in Table 1, treatment of
cells grown in TSH-containing medium and 50 ng/ml TNF, CHX, or both TNF
and CHX revealed that TNF significantly reduced iodide uptake by 45%
and NIS mRNA levels by 57%, but CHX (5 or 10 µg/ml) did not change
NIS mRNA levels by itself. However, 5 and 10 µg/ml CHX reversed the
inhibitory effect of TNF on iodide uptake, whereas 10 µg/ml CHX (but
not 5 µg/ml CHX) blocked the suppressive effect of TNF on NIS mRNA
levels. C16-ceramide inhibition of iodide uptake (54%) was
also reversible by simultaneous treatment with CHX.
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Hybridization of these same blots with a type I deiodinase (D1) cDNA probe revealed that both 5 and 10 µg/ml CHX were sufficient to quantitatively block the suppressive effect of TNF on D1 mRNA levels (16).
TGF-ß1 reduces NIS mRNA levels
TGF-ß1 suppressed NIS mRNA levels in a dose- and
time-dependent manner (Fig. 6). One-day
treatment with 50 ng/ml TGF-ß1 (Fig. 6, top right
panel) or two-day treatment with 6.25 ng/ml TGF-ß1
(Fig. 6, top left panel) reduced NIS mRNA levels by 76% and
80%, respectively. PF 4, a competitive inhibitor of
TGF-ß1 binding to the type I TGF-ß receptor (46), did
not reverse the suppressive effect of 6.25 ng/ml TGF-ß1
on NIS mRNA levels, as seen in Fig. 6, middle panel. The
TGF-ß1-dependent increase in ß-actin mRNA is opposite
to the decrease in NIS mRNA levels seen in the corresponding lanes of
the Northern blot of Fig. 6. This effect is consistent with the
TGF-ß1-induced change in young cells from cuboidal to
flattened stellate morphology.
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). TSH
increased the level of sphingomyelin 5-fold in young cells but did not
change the level of ceramide, in the absence of added TNF. Similar
results were obtained in aged cells (results not shown). In the
presence of 2 U/liter TSH, however, both ceramide and sphingomyelin
levels fell in young cells with TNF treatment (Table 1). However, the
decline of sphingomyelin was greater than that of ceramide, resulting
in a significant increase in the ceramide/sphingomyelin ratio.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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B (increased
expression of proinflammatory cytokines), PLA2 (arachidonic
acid, leukotrienes), tyrosine kinase, and phosphorylation of nuclear
transcription factors (6, 13, 14, 30, 31, 47). The arachidonic acid
second messenger pathway in liver cells has recently been shown to be
coupled to another signaling system, conversion of sphingomyelin to
ceramide by sphingomyelinase (32, 33). Human TNF binds only to the rat
p55 receptor for TNF (48, 49). This difference in range of receptor
binding by human and mouse TNF may explain, at least in part, the
difference in the time dependence of the suppressive effect of these
two TNF molecules on NIS mRNA noted in Fig. 2.
TNF increases the level of both sphingomyelin and ceramide in
FRTL-5 cells
TNF markedly increased the levels of both sphingomyelinase and
ceramide in both young and aged cells in the absence of TSH. Ceramide
is a second messenger that mediates programmed cell death (apoptosis)
induced by proinflammatory cytokines, such as TNF and IL-1ß, by heat
shock and by serum withdrawal (50). Growth factors such as
platelet-derived growth factor activate ceramidase and sphingosine
kinase, which convert ceramide to sphingosine-1-phosphate, a potent
antagonist of the apoptotic action of ceramide (50). TSH-induced
depletion of the TNF-enhanced sphingomyelin and ceramide pools in young
cells may be the result of both the growth-stimulating (anti-apoptotic)
effect of TSH and its second messengers cAMP, Ca2+ (51),
and sphingosine-1-phosphate (52) and increased utilization of ceramide
for the synthesis of mannose-inositol-phosphoceramide-anchored proteins
(53) of thyroid cells (54).
The effects of sphingomyelinase treatment on FRTL-5 cells are
consistent with increased conversion of sphingomyelin to ceramide
Addition of exogenous sphingomyelinase to FRTL-5 cells, a standard
method for elevating intracellular ceramide, produced the same
reduction in differentiated thyroid cell functions that normally occur
after activation of the endogenous sphingomyelinase by proinflammatory
cytokines (26, 32, 33). Recent observations that sphingomyelinase and
ceramide inhibit 5'-DI expression and activity in FRTL-5 cells (16, 17), as do TNF-, IL-1ß, and IFN- (4, 5), are also consistent
with activation of sphingomyelinase by proinflammatory cytokines in
this cell line.
TNF effects are protein synthesis-dependent
TNF effects on the expression of a number of genes, positive or
negative, are protein synthesis dependent. For example,
glucosylceramide (Glc-Cer) synthase, an enzyme that transfers a glucose
moiety from uridine diphosphate (UDP)-glc to ceramide, thus forming the
first member of a large family of glucosphingolipids, may be an
important branch in the intracellular signaling cascade stimulated by
increased production of ceramide (55). Both CHX and actinomycin D,
inhibitors of translational and transcriptional protein synthesis,
cause much of this synthase activity, which is induced by ceramide, to
disappear in 6 h (55). Treatment of U937 human promonocytic cells
with TNF, bacterial sphingomyelinase, or ceramide increases tyrosine
phosphorylation of a 23-kDa nuclear protein (P23) concomitantly with
the occurrence of DNA fragmentation (42). The tyrosine kinase
inhibitor, herbimycin A, inhibited tyrosine phosphorylation of P23 and
DNA fragmentation, suggesting that the p23 phosphoprotein may be
involved in the TNF-induced changes in the nucleus (42).
TGF-ß1 suppresses both
Na+/K+-ATPase and NIS expression and
activity
TGF-ß1, upon binding to a heteromeric complex of the
type I and type II TGF-ß receptors, activates one or more classes of
second messengers including mitogen-activated protein kinase (MAPK) and
Mad signaling pathways (37, 56). Some of the MAPK pathways are not
involved in the mitogenic response. In the budding yeast
Saccharomyces cerevisiae, for example, six MAPK pathways
have been identified, each of which regulates distinct functions such
as mating, response to high osmolarity, and spore formation (37). Mad
proteins are essential for embryogenesis and transduce signals for
specific subclasses of TGF-ß ligands (56). The cellular response to
TGF-ß1 in mammalian tissues is cell specific (36, 37, 38, 56). TGF-ß1 potently suppresses
Na+/K+-ATPase expression and activity in young
FRTL-5 cells (10) and, as shown here, also suppresses NIS mRNA. Thus,
TGF-ß1 has a dual action in inhibiting iodide
transport.
In vitro and in vivo aging of epithelial cells is associated with
increased TGF-ß expression
TGF-ß expression increases substantially with aging in FRTL-5
cells (15, 20). Aging also facilitates the TSH- and TNF-dependent
increase in expression of TGF-ß1 by FRTL-5 cells (15).
The family of antiinflammatory TGF-ß cytokines are potent inhibitors
of epithelial cell growth and function (35, 36). The marked reduction
in NIS mRNA levels in aged FRTL-5 cells suggests that reduced
125I uptake in this cell line and in the thyroids of
mammals with aging may be due primarily to inadequate numbers of NIS
molecules, perhaps secondary to progressive increase in TGF-ß
synthesis and secretion (10, 15).
Summary
TNF, sphingomyelinase, and ceramide, a TNF-inducible second
messenger in FRTL-5 rat thyroid cells, substantially reduce NIS mRNA
levels in this cell line. This pattern of inhibitory effects is
consistent with an important role for the sphingomyelinase signaling
pathway in mediating the inhibitory effect of proinflammatory cytokines
on thyroid cell function, including iodide uptake. The TNF-initiated
suppression of NIS expression is a protein synthesis-dependent process.
Because TGF-ß1 also reduces iodide uptake, but by a
different second messenger signaling pathway, a regulatory process
downstream from both the TNF-activated sphingomyelinase and
TGF-ß-activated MAP kinase and MAD protein pathways may be
responsible for the reduction in NIS expression. Aging also reduces NIS
mRNA levels and iodide transport, in part, by a substantial increase in
the expression and secretion of TGF-ß.
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Acknowledgments |
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Footnotes |
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Received July 22, 1997.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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, and
interferon- in human thyrocytes in suspension culture. J Clin
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I 5'-deiodinase, thyroid peroxidase, and thyroglobulin in FRTL-5 rat
thyroid cells. Endocrinology 136:881–888[Abstract]
. Endocrinology 131:863–870[Abstract]
(TNF-) and transforming
growth factor-ß1 (TGF-ß1) inhibit the
expression and activity of Na+/K+-ATPase in
FRTL-5 rat thyroid cells. J Interfer Cytok Res 17:185–195
(cachectin).
Endocrinology 125:76–84[Abstract]
and
interleukin 1 on FRTL-5 rat thyroid cells. Acta Endocrinol 123:203–210
, TSH, and aging regulate TGF-ß synthesis and
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. J Biol Chem 269:5757–5763 activates the sphingomyelin signal transduction
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J. P. Schroder-van der Elst, D. van der Heide, J. Kastelijn, B. Rousset, and M. Jesus Obregon The Expression of the Sodium/Iodide Symporter Is Up-Regulated in the Thyroid of Fetuses of Iodine-Deficient Rats Endocrinology, September 1, 2001; 142(9): 3736 - 3741. [Abstract] [Full Text] [PDF]
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T. Kogai, J. M. Hershman, K. Motomura, T. Endo, T. Onaya, and G. A. Brent Differential Regulation of the Human Sodium/Iodide Symporter Gene Promoter in Papillary Thyroid Carcinoma Cell Lines and Normal Thyroid Cells Endocrinology, August 1, 2001; 142(8): 3369 - 3379. [Abstract] [Full Text] [PDF]
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H.-C. Kang, M. Ohmori, N. Harii, T. Endo, and T. Onaya Pax-8 Is Essential for Regulation of the Thyroglobulin Gene by Transforming Growth Factor-{beta}1 Endocrinology, January 1, 2001; 142(1): 267 - 275. [Abstract] [Full Text] [PDF]
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M. Ohmori, N. Harii, T. Endo, and T. Onaya Tumor Necrosis Factor-{alpha} Regulation of Thyroid Transcription Factor-1 and Pax-8 in Rat Thyroid FRTL-5 Cells Endocrinology, October 1, 1999; 140(10): 4651 - 4658. [Abstract] [Full Text]
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