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Objective: The aim of this research was to investigate the effects of subacute use of lithium carbonate (Li2CO3), on serum T3, T4, thyroid stimulating hormone (TSH), parathyroid hormone (PTH) and calcium (Ca) levels and thyroid tissue. In addition, this research is important as one of the rare studies in which thyroid tissue was subjected to histological examination. Methods: Thirty-two male Sprague Dawley rats were assigned into groups consisting of eight animals each, based on weight; Group 1: Sham control, Group 2: Li2CO3+25 mg/kg, Group 3: Li2CO3+50 mg/kg and Group 4: Li2CO3+100 mg/kg. Li2CO3 was administered orally at varying concentrations, at 1 mL per day for 30 days. Serum samples were separated from blood obtained by intracardiac intervention. Serum T3, T4, TSH, PTH and Ca levels were measured by using an autoanalyzer and chemiluminescence. Thyroid tissue was examined under light microscopy after routine histopathological procedures. Results: T3, T4, PTH and Ca levels increased in rats treated with high-dose Li2CO3, whereas TSH levels were very low in all groups. In addition, thyroid tissue exhibited concentration-dependent histological alterations. Conclusion: Li2CO3, which was administered subacute high dose in rats, caused of increased T4 and T3 hormones levels, hyperparathyroidism and hypercalcemia in the early period. These results now need to be supported by further experimental and clinical studies.

Background: The concentration of trace elements and metals in the thyroid is the result of exposure, uptake, retention, and clearance. The specificity and selectivity of thyroid capacity to concentrate these elements relative to other tissues are not known. To obtain this information, we measured the tissue concentration of 26 elements in the thyroid, muscle, and fat of euthyroid human subjects and also in normal rats.

Nonylphenol (NP) is an endocrine-disrupting chemical (EDC) that can lead to thyroid disruption. We explored NP-induced toxicity in the rat thyroid and evaluated the mitigating effects of mulberry crude extract (MCE) on NP toxicity. First, we aimed to evaluate NP-induced thyroid disruption by dosing Sprague–Dawley (SD) rats with NP (0, 30, 90, or 270 mg/kg body weight) daily for 28 days. Second, we aimed to determine whether MCE had a detoxifying effect on NP-induced thyroid disruption by dosing SD rats with NP (270 mg/kg body weight) or/and MCE (30, 60, or 120 mg/kg body weight) daily for 28 days. We found that NP significantly inhibited free triiodothyronin (FT3) and free thyroxine (FT4) activity in rat serum (P

Background/aim We aimed to investigate whether there was a significant difference in TSH, T3, T4 values and histopathologically evaluated thyroid tissues between rats that received Isole Hydrolyzed Whey Protein (IHWP) at different doses regularly and rats fed with only standard feed. Material & methods Total 24 rats were divided into three groups with 8 rats in each group. First group were fed with standard feed for 12 weeks. Second group were given standard feed + daily 0.3 g/kg IHWP and rats in the third group standard feed + 0.5 g/kg IHWP for 12 weeks. Blood samples were collected from all rats before and after IHWP administration. All rats were then sacrificed, and thyroid tissues were histopathologically examined. Results Interfollicular connective tissue areas and TSH (0.35-4.90 µIU/L) were higher in the control group compared to 3cc IHWP and 5cc IHWP groups, while thyroid hormone T4 (0.7-1.48 ng/dL), and thyroid hormone synthesis parameters including intrafollicular colloid amount, follicular diameter and epithelial height were significantly higher in the 3cc and 5cc IHWP groups compared to the control group. Conclusion We think that regular daily use of IHWP may increase the synthesis of thyroid hormone due to its high amino acid content.

Lithium-based medications are used against many mental disorders, including Bipolar disorder and Alzheimer’s disease. However, lithium’s distribution in organs and cells is poorly characterized due to limitations in detection. This limits the ability to improve lithium-based treatments. To address this need, laser induced breakdown spectroscopy (LIBS) is developed for rapid and in situ detection of lithium in tissues. Pronounced lithium emissions are observed at 670.7 nm from the rat thyroid and salivary glands. The lithium emission intensity is positively correlated with tissue lithium concentration (R2=0.80). When subjects are administered lithium orally, thyroid lithium intensity increases (p

The present study was undertaken to optimize the dose of lithium, with an aim to increase the retention of I-131 in the thyroid follicles while maintaining the euthyroid state. 24 female Wistar rats weighing 110 ± 20 g were segregated into four groups. Animals in group I were fed standard laboratory feed and water throughout the period of experimentation. Animals in group II, III and IV were additionally fed with lithium in the form of lithium carbonate orally, at a dose of 10 mg/kg body weight, 20 mg/kg body weight, 30 mg/kg body weight respectively. The dose of lithium was started 1 week prior to radioiodine administration and continued thereafter for another 8 days. After 7 days of lithium treatment, 0.48 MBq of carrier-free I-131 was injected intraperitoneally into each rat, of the four groups. I-131 thyroidal uptake and biokinetics, as well as serum TSH, T3, T4 levels were estimated in all the treatment groups. A significant increase in the thyroid and whole body counts was observed after 4 and 24 h of I-131 aministration in lithium treated rats, compared to control animals. An increase in thyroidal effective t1/2 and serum TSH levels, along with decrease in the levels of serum T3 and T4 was observed with a dose of 20 mg/kg or higher. In Conclusion, a Lithium dose of 10 mg/kg body weight in rats could increase the uptake of I-131 in the thyroid, without disturbing the control circulating levels of thyroid hormones.

The study describes a mode of non-destructive simultaneous determination of bromine and iodine concentrations, by reactor instrumental neutron activation analysis (INAA) in the regime of short-term activation. Under the conditions of 1-minute activation in the neutron flux of 8.0·1013 n·cm−2·s−1, it was possible to determine reliably as little as 5·10−8 g bromine and about 10−7 g iodine in matrices of a given type and of the mass of about 5 mg dry weight. We applied this method for the determination of Br and I concentrations in the whole rat thyroid gland as well as for the halogen speciation in fractions separated from this organ.

The study of relations between structural organization and functions of microcirculatory networks is a major aim of modern microangiology. Such a structural aspect of microvessels (MVs) as their spatial arrangement has substantial influence on their transport and other functional properties. This paper describes a methodology of spatial correlation analysis for isotropic blood and lymphatic MVs which is based on a stereological estimator of the pair correlation function [g3D(r)] created recently by the authors for systems of elongated objects. The following main features of the methodology are presented: (i) interpretation of the shape of g3D(r) curves, (ii) their quantitative description by numerical parameters, and (iii) limitations of the method arising from statistical requirements to MVs under investigation. The methodology is considered in the light of multilevel sampling designs, which are typical for biomedical morphology. The estimator with its methodological framework is applied to perifollicular blood capillaries in the adult rat thyroid. Related methods for studying the spatial arrangement of MVs are thoroughly discussed in the paper.

Experimental mutagenic effect of acrylamide on thyroid gland cells was studied by an extended micronucleus test. Acrylamide in doses corresponding to 0.004-0.1 LD(50) increased the incidence of thyroid follicular cells (A-cells) with micronuclei and other karyological parameters in exposed rats after hemithyroidectomy. This cytogenetic effect allows regarding acrylamide as a mutagen for the thyroid gland and as a carcinogen for this organ.

The effect of a high bromide intake on the kinetics of iodide uptake and elimination in the thyroid and skin of adult male rats was studied. In rats fed a diet with sufficient iodine supply (25 microg I/d), the iodide accumulation in the skin predominated during the first hours after 131I iodide application. From this organ, radioiodide was gradually transferred into the thyroid. A high bromide intake (150 mg Br-/d) in these animals led to a marked decrease in iodide accumulation, especially by the thyroid, because of an increase in iodide elimination both from the thyroid and from the skin. In rats kept under the conditions of iodine deficiency (1 micro I/d), the iodide accumulation in the thyroid, but not in the skin, was markedly increased as a result of a thyrotropic stimulation. The effect of a high bromide intake (100 mg Br-/d) in these animals was particularly pronounced because the rates of iodide elimination were most accelerated both from their thyroid and from their skin.

Extracellular matrix (ECM) and basement membrane (BM) components were studied by immunohistological methods in native rat thyroid tissue, and in rat thyroid tissue and FRTL-5 cells cultured in a three-dimensional alginate bead system. In all three situations, the presence of collagen IV, laminin, perlecan, and fibronectin was demonstrated. There were marked differences between rat thyroid tissue and FRTL-5 cells in culture. Rat thyroid tissue maintained a follicular structure, whereas FRTL-5 cells did not form follicles. Rat thyroid cells multiplied more slowly than FRTL-5 cells and thyroglobulin (Tg) was visible in the follicular lumen, while in FRTL-5 cells Tg was only seen intracellularly. Tg iodination was much lower in FRTL-5 cells than in rat cells. In rat thyroid cells, positive staining for collagen IV, laminin, and perlecan was seen in thin membranes around individual follicles, and for fibronectin around groups of follicles. In FRTL-5 cells, these ECM/BM components could be identified, but were not organized into equally regular networks around groups of cells. These results demonstrate that of the two types of cells examined, primary cultures of rat thyroid cells in alginate beads maintain structural and functional similarities to native thyroid tissue and would therefore be suitable for future in vitro studies of thyroidal ECM/BM and their interrelationship with growth and function of this organ. FRTL-5 cells cultured in alginate beads show some functional, but not structural similarities to native thyroid tissue and so would be less valuable for use in such studies.

Rat thyroid cell strain FRTL-5 is widely used to analyze thyroid stimulators, and responds to purified hCG with increased cyclic AMP production. The aim of this study was to determine the in vitro thyrotropic activity of an immunological hCG molecule according to gestational age during normal pregnancy using the FRTL-5 cell culture system. Sera were collected from 7 normal nonpregnant control and a total of 72 normal pregnant women. Seventy-two pregnant women consisted of 40 women in the first trimester (7–14 weeks’ gestational age (GW) (group I)), 16 women in the second trimester (15–28 GW, group II), and 16 women in the third trimester (29–40 GW, group III). Concentrations of serum hCG and FT4 of group I were higher than those of groups II and III (p < 0.001). In the in vitro assay, the supernatants were subjected to radioimmunoassay for cAMP. In order to analyze in vitro thyrotropic activity of an immunological hCG molecule, cAMP accumulation rate expressed as cAMP accumulation (nM) divided by maternal serum concentration of hCG (IU/ml) was determined in all three groups. By regression analyses, a statistically significant positive correlation was observed between serum hCG concentration and cAMP accumulation in group I (r = 0.399; p < 0.05), group II (r = 0.915; p < 0.0001) and group III (r = 0.671; p < 0.01). cAMP accumulation rate in group I (0.355 ± 0.022, mean ± SE) was significantly low when compared with group II (0.508 ± 0.051) (p < 0.01) and group III (0.556 ± 0.063) (p < 0.001). Thus, it was found for the first time that the in vitro thyrotropic activity of an immunological hCG molecule in the first trimester was lower than those of the second and the third trimesters. In terms of the in vitro thyrotropic activity, an immunological hCG molecule in the first trimester differs from that of the later trimesters.

We have isolated a rat thyroid cDNA encoding a novel rat receptor-type tyrosine phosphatase protein. This gene, on the basis of its homology to another tyrosine phosphatase, the recently isolated human DEP-1/HPTP eta, has been named r-PTP eta. In rat thyroid cells the r-PTP eta gene acts as a differentiation marker, Indeed, the block of thyroid cell differentiation induced by viral and cellular oncogenes is associated with the inhibition or marked reduction of the expression of this gene and its expression is positively regulated by thyrotropin, the physiological stimulator of thyroid cell growth. (C) 1997 Academic Press.

It has been suggested that, for mechanistic reasons, certain tumors found in experimental animals should be discounted when evaluating carcinogenic effects. The questioned tumors are: mouse liver, rat thyroid follicular cell, bladder and kidney (male rat), forestomach (mouse and rat, gavage route), and lung (mouse and rat, inhalation of particles). We sought to determine the effects of discounting those tumors on classification of chemicals as carcinogens in animals. We looked at carcinogenicity data for chemicals studied in NCI-NTP bioassays and/or reviewed in IARC monographs and we found that deleting the questioned tumors would have significant impact on evaluations of carcinogenicity in animals. Fifty-six of 234 (24%) chemicals determined to be carcinogenic in the NCI-NTP bioassay program would no longer be considered carcinogenic: 102 (44%) would have weaker evidence of carcinogenic effects. Thirty-three of 361 (9%) chemicals determined by IARC to have "limited" or "sufficient" evidence of carcinogenicity would no longer be considered carcinogenic; 119 (33%) would have weaker evidence of carcinogenic effects. Because such a large number of chemicals currently considered carcinogenic would be affected by categorical deletion of tumors and because we are not aware of data that would justify such categorical deletions, it would be preferable to consider mechanistic justifications for discounting tumors on a case-by-case basis for each individual chemical. Deletion of tumors on a categorical basis has serious implications for regulation of toxic chemicals and for public health.

Kamel MA Hassanin,1 Samraa H Abd El-Kawi,2 Khalid S Hashem1 1Department of Biochemistry, Faculty of Veterinary Medicine, 2Department of Histology, Faculty of Medicine, Beni-Suef University, Beni-Suef, Egypt Background: Nanotechnology has enabled researchers to synthesize nanosize particles that possess increased surface areas. Compared to conventional microparticles, it has resulted in increased interactions with biological targets. Objective: The objective of this study was to determine the protective ability of selenium nanoparticles against hexavalent chromium-induced thyrotoxicity. Design: Twenty male rats were used in the study, and arbitrarily assigned to four groups. Group 1 was the control group, and was given phosphate-buffered saline. Group 2 was the chromium-treated group and was given K2Cr2O7 60 µg/kg body weight intraperitoneally as a single dose on the third day of administration. Group 3 was the nano-selenium-treated group and was given selenium nanoparticles (size 3–20 nm) 0.5 mg/kg body weight intraperitoneally daily for 5 consecutive days. Group 4 was the nano-selenium chromium-treated group, which received selenium nanoparticles for 5 days and a single dose of K2Cr2O7 on the third day of administration. Materials and methods: Blood samples were collected from rats for measuring thyroid hormones (free triiodothyronine [T3] and free thyroxine [T4]) and oxidative and antioxidant parameters (malondialdehyde [MDA], reduced glutathione [GSH], catalase, and superoxide dismutase [SOD]). Upon dissection, thyroid glands were taken for histopathological examination by using paraffin preparations stained with hematoxylin and eosin (H&E) and Masson’s trichrome. Immunohistochemical staining was performed for detecting cellular proliferation using Ki67 antibodies. Results: The present study shows that K2Cr2O7 has a toxic effect on the thyroid gland as a result of inducing a marked oxidative damage and release of reactive oxygen species. This was shown by the significant decrease in free T3 and T4 and GSH levels, which was accompanied by significant increases in catalase, SOD, and MDA in the chromium-treated group compared to the control group. Se nanoparticles have a protective effect on K2Cr2O7-induced thyroid damage, as a result of correcting the free T3 and T4 levels and GSH, catalase, SOD, and MDA compared to the K2Cr2O7-treated group. Administration of nano-selenium alone in the nano-selenium-treated group had no toxic effect on rats’ thyroid compared to the control group. The biochemical results were confirmed by histopathological, immunohistochemical and pathomorphological studies. Keywords: chromium, selenium nanoparticles, thyrotoxicity, protective effect

Noradrenaline and ATP evokes a transient increase in the intracellular calcium concentration ([Ca2+]i) in FRTL-5 cells. In a previous study, we showed that 1,25-dihydroxyvitamin-D3 (1,25(OH)2-D3) increases the ATP evoked changes in [Ca2+]i. In the present paper, we found that pre-incubating the cells with 10 nM 1,25(OH)2-D3 for 48 h did not affect the noradrenaline-evoked increase in [Ca2+]i. We subsequently examined if this could be due to an effect of 1,25(OH)2-D3 on α1-adrenergic receptor number, or receptor affinity. Pretreatment with 10 nM 1,25(OH)2-D3 for 48 h decreased the binding of the α1-adrenergic specific antagonist [3H]prazosin by 55% (Bmax for 1,25(OH)2-D3 treated = 27.6 ± 5.0 fmol/mg protein, untreated = 61.7 ± 5.4 fmol/mg protein). No effect of 1,25(OH)2-D3 on the affinity for [3H]prazosin was observed. The effect of 1,25(OH)2-D3 on the [3H]prazosin binding was both time- and dose-dependent and could first be seen after 8–12 h of 1,25(OH)2-D3 treatment, indicating a genomic effect. The effect of 1,25(OH)2-D3 could be abolished with the protein synthesis inhibitor cycloheximide. No effect on the [3H]prazosin binding could be seen after a 48 h preincubation with 100 nM of either 24,25-dihydroxyvitamin D3 and 25-dihydroxyvitamin D3, indicating that the effect of 1,25(OH)2-D3 was specific. The cellular cAMP concentration was decreased after 48 h treatment with 10 nM 1,25(OH)2-D3. When TSH was replaced with dibutyryl cAMP or forskolin the [3H]prazosin binding increased. 1,25(OH)2-D3 also reduced the dibutyryl cAMP and forskolin stimulated [3H]prazosin binding. In addition, 1,25(OH)2-D3 reduced the [3H]prazosin binding in TSH deficient media. Our results suggest that 1,25(OH)2-D3 reduces the number of α1-adrenergic receptors via a dual mechanism: by reducing cAMP production and by affecting some mechanism(s) downstream from the production of cAMP.

The sodium iodide symporter (NIS) is responsible for the accumulation of iodide in the thyroid gland. This transport process is involved in numerous thyroid dysfunctions and is the basis for human contamination in the case of exposure to radioactive iodine species. 4-Aryl-3,4-dihydropyrimidin-2(1H)-ones were recently discovered by high-throughput screening as the first NIS inhibitors. Described herein are the synthesis and evaluation of 115 derivatives with structural modifications at five key positions on the pyrimidone core. This study provides extensive structure-activity relationships for this new class of inhibitors that will serve as a basis for further development of compounds with in vivo efficacy and adequate pharmacokinetic properties. In addition, the SAR investigation provided a more potent compound, which exhibits an IC(50) value of 3.2 nM in a rat thyroid cell line (FRTL5).

The impact of lead as an environmental pollutant on the I-131 uptake and retention in rat thyroid was assayed alone and in combination with lithium treatment. Lead treatment significantly stimulated the 2- and 24-h uptake of I-131 in the thyroid, and the 24-h uptake showed the maximum stimulation after 3 mo of lead treatment. On the contrary, lithium supplementation reduced the uptake significantly and the maximum decrease was noticed after 2 mo of lithium administration. Further, simultaneous lead and lithium treatment resulted in more pronounced increase in the uptake of I-131 by the thyroid, which was maximum after 3 mo of combined treatment. The thyroidal biological half-life of I-131 (T biol) was found to be increased significantly following lead and lithium treatments when given separately. Interestingly, combined lead and lithium treatment given up to 2 mo further prolonged theT biol of I-131, thus reflecting its increased retention.

To examine a possible role for C-type natriuretic peptide (CNP) in the thyroid, we studied the ability of this peptide to compete with atrial natriuretic factor (ANF) binding to FRTL-5 rat thyroid cells. Rather than competing for ANF binding, CNP significantly elevated [ 125 I]ANF binding above control at both 23° and 2°C. The increase in ANF binding was due largely to a threefold increase in receptor affinity in the presence of CNP (control, K d = 8.7 n M ; 1 μ M CNP, K d = 3.1 n M ). Despite the failure to compete for ANF binding, CNP was almost as effective as ANF at inducing cGMP production in FRTL-5 cells. Competition binding studies using [ 125 I]CNP indicated the presence of a relatively low-affinity site for CNP ( K d = 77 n M ) that bound ANF with equal affinity. These results show for the first time that ANF receptor binding can be positively regulated by the related natriuretic peptide, CNP.

The effects of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] on TSH and the 3',5'-cyclic adenosine monophosphate (cAMP) analogue 8-(4-chlorophenylthio)-cAMP-stimulated cell growth and iodide uptake were studied in a rat thyroid cell line (FRTL-5). 1,25-(OH)2D3 inhibited both TSH and 8-(4-chlorophenylthio)-cAMP-induced cell proliferation with the maximum effect at 100 nmol/L. The inhibitory effect of 1,25-(OH)2D3 (10 nmol/L) on TSH and 8-(4-chlorophenylthio)-cAMP-stimulated iodide uptake was observed after 2 days of incubation, and the effect was maximal after 4 days. The inhibition was dose-dependent and maximal at 100 nmol/L 1,25-(OH)2D3. 1,25-(OH)2D3 (10 nmol/L, 4 days) increased the median concentrations of TSH required to stimulate both cAMP production and iodide uptake half-maximally by 124 and 187%, respectively, whereas the median 8-(4-chlorophenylthio)-cAMP concentration was not changed. Lineweaver-Burke plots revealed that 1,25-(OH)2D3 reduced the Vmax of the sodium-driven iodide carriers to 30% of the control cells without effect on the Km. Iodide efflux was only slightly increased in the 1,25-(OH)2D3-treated cells. In conclusion, 1,25-(OH)2D3 potently inhibited the TSH-stimulated growth and iodide uptake by FRTL-5 cells both by reducing the TSH-stimulated cAMP production and by attenuating the stimulatory effects of cAMP.

Thyroid autoregulation has been related to intraglandular content of an unknown putative iodocompound. The thyroid is capable of producing different iodolipids such as 6-iodo-deltalactone (ILdelta) and 2-iodohexadecanal (2-IHDA). Data from different laboratories have shown that these iodolipids inhibit several thyroid parameters. ILdelta has an antigoitrogenic action but no data about the action of 2-IHDA on this parameter has been published.to study the action of 2-IHDA on methimazole (MMI)-induced goiter and analyze if this compound can cause the involution of preformed goiter.Administration of MMI to rats during 10 days increased thyroid weight by 112%. This effect was significantly inhibited by the simultaneous injection of 20mug/day of 2-IHDA (51% vs. MMI) while iodine or non iodinated hexadecanal were without action. Thyroidal proliferating cell nuclear antigen (PCNA) content was increased by MMI while 2-IHDA decreased this value (control: 100%; MMI: 190+/-11; MMI+2-IHDA: 134+/-10). Serum TSH was increased after MMI administration and 2-IHDA did not modify this parameter (control: 1.89+/-0.10; MMI: 8.19+/-0.93ng/ml; MMI+2-IHDA: 7.38+/-0.72). Treatment with MMI increased thyroidal cAMP content (control: 16.1+/-0.82, MMI: 42.4+/-4.6 fmol/mg protein) while injection of 2-IHDA significantly decreased this value (22.3+/-2.0). Goiter prevention by 2-IHDA was also observed at 30 days of treatment reducing total number of cells (51% inhibition) and epithelial height (81% inhibition). Goiter involution was induced after withdrawal of MMI and injection with 2-IHDA, KI or saline. 2-IHDA led to a reduction of 74.5% in thyroid weight after 3 days while spontaneous involution (saline) was only of 32%. KI failed to alter this value. This significant involution was accompanied by a reduction in the number of cells (66%). Administration of the iodolipids did not produce significant changes in several serum parameters such as total T(3) and T(4), cholesterol, transaminases, urea and creatinine.2-Iodohexadecanal, as 6-iodo-deltalactone, prevents goiter growth in rats and opens a potential therapeutic application of iodolipids.

FRTL-5 cells are used in many laboratories as an in vitro system of thyroid follicular cells since they share many properties of human thyrocytes. However, the use of FRTL-5 cells for experimental modifications is limited by low transfection efficiencies of lipid-based transfections and the need for cumbersome viral transduction protocols. A new technology - nucleofection - has become available for cell lines that are difficult to transfect. Here, we report the application and optimization of this method in FRTL-5 cells. Using the green fluorescent protein (GFP) as a reporter gene, FRTL-5 cells were easily transfectable with efficiencies over 60%. In addition, the simultaneous transfer of siRNA against GFP was feasible and allowed suppression of GFP over at least 4 days. Furthermore nucleofection was successful for establishing stable FRTL-5 cell clones. In conclusion, this optimized fast and efficient nucleofection protocol offers new properties for the experimental use of FRTL-5 cells.

To elucidate the gene regulation of the thyroid-cell growth-promoting activity by human chorionic gonadotropin (hCG), we investigated the effect of hCG on c-myc proto-oncogene expression in cultured rat FRTL-5 cells by the Northern blot method. hCG induced c-myc mRNA expression, which peaked at 60-120 min. A dose-dependent increase in c-myc mRNA levels was also ascertained. In the presence of crude immunoglobulin G (IgG) from 2 patients with primary hypothyroidism who had blocking type TSH-receptor antibody, c-myc mRNA expressions induced by hCG were decreased to 82% and 62%, compared with that in the presence of normal IgG. The present results suggest that the expression of c-myc mRNA is a part of the molecular mechanism through which hCG regulates the proliferation of thyroid cells, and that hCG-induced c-myc mRNA expression is presumed to be mediated in part by TSH receptors.

We investigated the effect of thyroid stimulating hormone (TSH) on the expression of hexokinase I mRNA by cultured rat thyroid FRTL5 cells. TSH stimulated hexokinase I gene expression in a time- and dose-dependent manner. An increase in hexokinase I mRNA was detected after 3 h of incubation with TSH, and a maximum was reached after 12 h showing about 2.5-fold increase at 1mU/ml TSH. A nuclear run-on transcriptional assay showed that the effect of TSH on hexokinase I mRNA was due to an increase in the rate of gene transcription. (Bu)2cAMP and forskolin also increased hexokinase I mRNA expression to almost the same extent as TSH. These findings suggest that TSH stimulates hexokinase I gene expression at the transcriptional level via the cAMP-dependent pathway.

The effects of 4-h incubation in the presence of melatonin and N-acetylserotonin on the incorporation of [ 3 H]-thymidine into DNA of the rat thyroid lobes were investigated. Additionally, thyroid lobes were incubated in the exposure to melatonin with thyrotropin jointly. Melatonin, when applied in the lowest concentration examined (10 −9 M), inhibited [ 3 H]-thymidine incorporation, the effect of other concentrations (10 −6 M – 10 −8 M) being not significant. N-acetylserotonin (10 −6 M) did not affect the rate of incorporation of that labelled nucleoside. As expected, thyrotropin enhanced the [ 3 H]-thymidine incorporation into DNA of thyroid lobes. Melatonin (10 −7 M) suppressed that stimulatory effect of thyrotropin. The participation of melatonin in the regulation of thyroid growth processes is considered.

Changes in morphology and cell kinetics are described in a rat thyroid transplantable tumour (TTT) during the first few transplant generations. The growth of TTT in animals was possible only with an increased circulation level of the thyroid stimulating hormone (TSH). With serial transplantation subcutaneously in isologous animals, the morphology of TTT changed dramatically from that of a follicular tumour in the 3rd passage to become, by the 9th generation, a poorly differentiated tumour with a trabecular arrangement of cells. This change in tumour morphology was accompanied by an increase in the number of proliferating cells--mitotic index (MI), [3H]thymidine labelling index (LI), growth fraction (GF)--and cell loss factor (O) as well as a decrease in the cell cycle time (Tc) and potential population doubling time (TPD). TTT belongs to the class of tumours with a low proliferative activity and might be used in a variety of cell kinetic, radiobiological and chemotherapy studies.

Leptin has stimulatory effects on the hypothalamic-pituitary-thyroid axis and on deiodinases activities. Here, we evaluated the effect of leptin injection upon in vivo and in vitro thyroid 125I uptake (RAIU). We designed two experiments: acute leptin (LepA) with a single dose of leptin (8 microg/100 g BW/sc), and chronic leptin (LepC), injected with the same dose of LepA, once a day, for 6 days. In parallel, control groups were saline-injected. For in vivo study, part of the animals were injected with 125I (3700 Bq) and killed after 15 or 120 min. In vivo thyroid RAIU was not changed in LepA animals. However, LepC animals showed higher in vivo thyroid RAIU (15 min:+130% and 120 min:+72%; p0.05). For in vitro study, the other animals were killed and their thyroids were incubated with 125I. Thyroids explants from LepA and LepC groups presented lower thyroid 125I content (-32% and -29% p0.05, respectively). The amount of our data suggest that, in vitro, leptin causes a direct inhibition of the rat thyroid RAIU, but in vivo, the effect of leptin was different according to the treatment period, which indicates that other indirect mechanisms are involved in the in vivo leptin chronic stimulation of the thyroid gland.

WOS: 000240899900006, PubMed ID: 16999600, Objectives: This study had two aims; (1) to describe the cell death pathway (apoptosis or necrosis) induced by a low and high dose of radioiodine (I-131) in rat thyroid tissue in in vivo conditions and (2) to determine the role of apoptosis in the development of "stunning effect" in the thyroid tissue with low and high doses of I-131 application. Design: The experimental group consisted of 18 rats; low and high I-131 doses with a 1-week interval were administered to this group. At first, low doses were injected intraperitoneally (i.p.) (net injected dose was 51.54 +/- 8.6 mu Ci). After 1 week of the low-dose injection, high doses were also injected (net injected dose was 934.9 +/- 211.8 mu Ci). Thyroidal I-131 uptakes for both low- and high-dose applications were calculated by using a gamma camera after 24 hours of injections. Immediately after the uptake calculation, thyroid tissues were resected. A control group of 10 rats was also included in the study; in this group, I-131 was not administered. Thyroid tissues of this group rats were also resected. DNA was extracted from thyroid tissues, and damage was examined with the "DNA ladder by agaroz gel electrophoresis." Results: Thyroidal I-131 uptakes were calculated as 11.3% +/- 3.6% and 9.8% +/- 5.3% at the 24th hour after low- and high-dose I-131 applications, respectively. When the low- and high-dose uptake values were compared for each rat; a significant relationship was not found between thyroidal uptakes and injected low and high doses of I-131. When the chromosome images were examined, there was healthy DNA appearance in I rat; in 4 rats, only necrotic hyperfragmentations were observed; in 9 rats, both apoptotic specific fragmentations and necrotic hyperfragmentations were observed; and in 4 rats, apoptosis, necrosis, and healthy DNA appearances were seen together. In none of the rats, specific fragmentations concordant only with apoptosis was found. When the thyroidal uptake alterations were taken into consideration, significant difference was not found between first and second uptake calculations (p = 0.28). No significant relationship was also observed between thyroidal uptake alterations and apoptosis-necrosis-healthy DNA findings. Additionally, when we take into consideration the DNA results of only 13 of the rats that had reduced thyroidal uptake, a significant relationship could also not be observed between reduced uptake and apoptotic, necrotic, or healthy tissue findings. Interestingly, apoptotic and necrotic tissue or only necrotic, tissue findings were observed in the other 5 rats which had increased thyroidal uptake. Conclusions: Following I-131 administration, two types of cell death-both apoptosis and necrosis findings-have been observed in most of the rats. We think that the decreased uptake values are because of the probable stunning effect in thyroid tissue. We also investigated whether the stunning effect is related to apoptosis. According to our results, it can be concluded that the stunning effect is not related to tissue damage, cell decrease, or cell death. Alternatively, we think that this can be related to a radiation-induced reduction of iodine uptake/metabolism or a modified iodine transport mechanism. For further in vivo studies, this experimental model using normal rat thyroid tissue may be useful in investigating the cell death pathways induced by I-131 and its probable roles in the development of the stunning phenomenon.

This paper studies calcitonin (CT) transport across the C-cell-blood (CCB) barrier in normal rats. The efficiency of this transport is expressed as endogenous calcitonin bioavailability (F(CT)), i.e., that portion of CT molecules extruded by the thyroid C-cell basal pole that enters the circulating blood. Because currently F(CT) cannot be estimated directly, a novel methodology was used for its estimation. The essence of this methodology is to assess the CT level before and after the CCB barrier, to study these input-output CT relationships mathematically, and to find the F(CT) range allowed by the relationships. In this context, the subplasmalemmal granule numerical density in the C-cell basal pole (X) and the CT concentration in the right ventricular blood (Y) were found to be highly correlated: r(xy) = 0.922, P0.001; the covariance coefficient rho(xy) = 0.9980, P0.0001. Clearly, the overall variance of these input-output relationships in the covariance model (square root Var(xy) = 6.32) is explained, specifically, by CT retention (R(CT)) variability at the CCB transport stages. The greater the R(CT) mean value in the studied rats, the greater is the impact of R(CT) variability on Var(xy). The estimated variance caused by R(CT) (Var(CCBR)) makes it possible to determine R(CT) and F(CT) (F(CT) = 100% - R(CT)). Thus we estimated Var(CCBR) as Var(CCBR)Var(xy) - CV(RIA)(2), where CV(RIA)(2) is CT assay variance: square root Var(CCBR) = 6.00% (Por = 0.95). We then estimated F(CT) as the value range that does not contradict the Var(CCBR) obtained: 62%F(CT)100% (Por = 0.95).

Studies in hypothyroid rats show that, when infused with a combination of thyroxine (T4) plus triiodothyronine (T3) to normalize thyrotropin (TSH), euthyroidism in all organs is only ensured when T(4) and T(3) are administered in a ratio as normally secreted by the rat thyroid. As substitution with T(4)-only results in an abnormal serum T(4)/T(3) ratio, it is also possible that in humans, euthyroidism does not exist at the tissue level in many organs, considering that iodothyronine metabolism in the human and the rat share many similar mechanisms. Recent reports in which cognitive function and well-being are compared in patients with primary hypothyroidism substituted with T(4)-only versus substitution with T(4) plus T(3) result in controversial findings in that either positive or no effects were found. In all these studies T(3) was used in the plain form that results in nonphysiologic serum T(3) peaks. In these studies it is suggested that substitution with T(3 )should preferably be performed with a preparation that slowly releases T(3) to avoid these peaks. In the study reported here we show that treatment of hypothyroid subjects with a combination of T(4) plus slow-release T(3) leads to a considerable improvement of serum T(4) and T(3) values, the T(4)/T(3) ratio and serum TSH as compared to treatment with T(4)- only. Serum T(3) administration with slow-release T(3) did not show serum peaks, in contrast to plain T(3).

The effects of kojic acid (KA) on thyroidal function were studied by single-dose administration in rats and in cultured rat thyroid cells (FRTL-5 cells). In rats receiving a single dose of 1,000 mg/kg KA orally, the 125I uptake from blood into the thyroid gland was significantly lower than that of the control group from 30 min to 24 hr after administration. The 125I organification activity of the KA groups was significantly lower than control from 30 min to 6 hr after administration. However, the 125I organification activity at 24 hr or 48 hr after administration recovered enough to be nearly comparable with the control group. In the study in FRTL-5 cells, KA inhibited iodine organification dose-dependently, but did not inhibit iodine uptake. These results suggest that the observed lower iodine uptake activity in the single-dose administration study in rats was due to the inhibition of iodine organification caused by the oral administration of KA, consequently decreasing iodine in the entire thyroid gland. Although serum T4 showed a tendency to decrease from 2 hr to 48 hr after administration of KA, serum TSH did not show any evident change associated with KA in the single-dose administration study in rats. Based on these results, it is presumed that a massive dose or long administration period might be needed to decrease serum T4 and increase serum TSH. From these results, it is presumed that KA affected thyroidal function when given at a massive dose or in a long administration period by inhibiting iodine organification in the thyroid.

PURPOSE: To study quantitatively C cells in the thyroids of non-isogenic rats to determine the possible effects of pinealectomy on the number of these cells, and consequently on the synthesis and secretion of calcitonin. METHODS: Twenty male rats of an outbred strain (200-300 g) were used in the present study. One group of 10 animals was pinealectomized 50 days prior to sacrifice. Thyroid tissue was stained for calcitonin (Dako Corporation) at a 1:1500 dilution. The number of C cells observed was expressed as number of cells/cm². Data were analyzed statistically by Mann-Whitney test. RESULTS: The number of C cells in pinealectomized and normal animals ranged from 489 to 2084 per cm² and 227 to 1584 per cm², respectively, a difference that was statistically significant (P

The FRTL-5 rat thyroid cell line is widely used for studies of thyrocyte function and growth. The objective of the present study was to investigate the effects of hepatocyte growth factor (HGF) on FRTL-5 cells. HGF has previously been known to be a potent regulator of thyrocyte growth and differentiation. Met, the receptor for HGF was expressed in FRTL-5 cells, as well as in primary cultures of porcine thyrocytes included in the study as control. On HGF stimulation Met was tyrosine phosphorylated in both porcine and FRTL-5 cells, indicating an activation of the receptor. Addition of HGF induced changes of cell shape, scattering and proliferation of the porcine thyrocytes, but not in the FRTL-5 cells; yet, a functional coupling of Met to the p85 subunit of the phosphatidylinositol-3'-kinase (PI3'-K) in coprecipitation experiments, formation of focal adhesions detected in immunofluorescence staining with an antivinculin antibody, and induction of c-fos mRNA in Northern blot analysis was observed in FRTL-5 cells, showing a transduction of the HGF/Met signal. In summary, despite the expression of apparently functional Met, the FRTL-5 cells are unable to properly respond to HGF.

The dose absorbed fraction of rat thyroid by internal deposit of 131I has been calculated as a function of effective diameter of thyroid. The calculations were done using two types of Monte Carlo simulations: one was by a simple energy-loss calculation in spherical volume according to the electron stopping power, and another by a more realistic simulation using Monte Carlo N-Particle Transport code system Version 4A (MCNP). These two calculations were consistent with each other within a deviation of 5%. The absorbed fractions in spherical thyroid were drastically changed up to 5 mm diameter, and then almost all energy was deposited within 10 mm diameter. For the practical application to the animal experiment, the absorbed fractions of ellipsoid-shaped thyroids were also calculated for 1-, 4- and 9-week-old rats, where the fractions were estimated to be 0.61, 0.67 and 0.68, respectively. It was also found that the absorbed fraction of the ellipsoid with various dimensions can be simulated by a calculation for spherical volume with a comparable effective diameter.

The sympathetic nervous system plays a role in the regulation of thyroid function. In FRTL-5 rat thyroid cells, norepinephrine (NE) acutely depresses intracellular I- by increasing I- efflux. The present study was undertaken to determine the effect of NE on iodide transport after a longer time period. NE inhibited the ability of thyrotropin (TSH) to induce iodide uptake by FRTL-5 cells after 48 or 72 hours, but not after 24 hours. The effect of NE was more evident with increasing concentrations of TSH. NE did not modify the rate of I- efflux. Inhibition was associated with a decrease in the Vmax and no change in the Km for iodide influx. To determine if this was a generalized effect of NE on thyroid cell membrane, the uptake of alpha-aminoisobutyric acid (a nonmetabolizable aminoacid) and of 2-deoxyglucose was measured. NE did not inhibit TSH stimulation of the uptake of the two compounds. NE inhibited the action of dibutyryl cAMP (dbcAMP) on iodide uptake in a similar manner to TSH, but did not alter the cyclic adenosine monophosphate (cAMP) levels increased by TSH. The effects of different adrenoreceptor agonists and antagonists demonstrated that norepinephrine acts through an alpha1-adrenergic receptor.

Alterations in the superoxide dismutase (SOD) content of thyroid tissues occurring in association with thyroid dysfunction have been reported. In this study, the Mn-SOD content was found to increase in thyroid tissues of rats administered thyroid stimulating hormone (TSH) and in thyrocytes cultured in medium supplemented with TSH. Furthermore, in the thyroid glands of rats whose serum TSH level was elevated by inhibiting the synthesis of T3 and T4 by 6-methyl-2-thiouracil, the Mn-SOD increased as the TSH concentration increased. In the cultured thyrocytes, the increase in Mn-SOD induced by TSH was inhibited by the C-kinase inhibitor H7. These findings suggest the induction of Mn-SOD by TSH in thyroid cells and point to a role of C-kinase in this process, thereby indicating that a close relationship exists between the serum TSH level and the change in Mn-SOD content in thyrocytes with thyroid dysfunction.

Chronic hypoxia inhibits rat thyroid function in vivo. To determine possible mechanisms, we studied the effect of hypoxia on iodide uptake, the involvement of second messengers, and cell membrane permeability in rat thyroid FRTL-5 cells. Since sublethal heat stress protects tissues from ischemia, we also determined effects of heat stress. The initial rate of iodide uptake in untreated cells was between 12.98 and 15.28 pmol/micrograms DNA/min. Hypoxia (5% O2) increased the rate of uptake in a time-dependent manner. Heating cells at 45 degrees C for 15 min (heat shock) prior to exposure to hypoxia for 3 days inhibited the increase in the initial rate of I-uptake. Using fura-2, we found that the resting [Ca2+]i in suspended FRTL-5 cells was 65 +/- 7 nM (n = 16). [Ca2+]i was not increased in cells exposed to hypoxia for 1 day, while a 3-day exposure increased [Ca2+]i by 43 +/- 4% (p0.05); no additional increase occurred after 7 days of exposure. When cells were heated prior to hypoxia exposure for 3 days, the hypoxia-induced increase in [Ca2+]i did not occur. Similar observations were found with inositol trisphosphates (InsP3). Exposure of cells to hypoxia for 3 days increased InsP3 from 0.08 +/- 0.02 (n = 5) to 0.32 +/- 0.04% total cpm (n = 5, p0.05), but sublethal heating of cells prior to hypoxia exposure prevented the increase. Three-day hypoxia increased PKC activity in the membrane fraction (from 67 +/- 7 to 86 +/- 4% of total activity, p0.05), and heat shock inhibited these changes also. Immunoblots showed that hypoxia treatment alone and heat shock plus hypoxia resulted in the translocation of PKC-alpha, -delta, -epsilon, and -zeta isoforms, whereas heat shock alone translocated only PKC-beta I, -beta II, and -zeta. Cell membrane integrity was assayed by trypan blue exclusion. Hypoxia alone for 3 days did not affect membrane permeability, but only 49 +/- 3% of cells excluded trypan blue when a 3-day hypoxia exposure was followed by a 6 h reoxygenation. Heat shock prior to hypoxia and reoxygenation protected cell membrane function. Heat shock also induced heat shock protein 70 kDa (HSP-70) synthesis at the transcriptional level. Results suggest that heat shock protects FRTL-5 cells from hypoxic injury, perhaps by inhibiting the initial rate of iodide uptake and second messengers. It is likely that HSP-70 plays an essential role in the process of protection.