Cryopreservation of Encapsulated Axillary Buds of Clitoria ternatea (L.)

BACKGROUND

Clitoria ternatea is a brain revitalizing legume, with immense pharmacological value including antimicrobial, antioxidant and anticancer. The lack of a commercial cultivation has led to its' over collection from the wild to meet the demand of herbal pharmaceutical sector and the species is now rare in the wild. Hence, the plant needs to be conserved. Cryopreservation of the species would supplement the conventional conservation strategies in the field or seed bank.

OBJECTIVE

The objective of the study was to evolve an efficient and simple protocol for the cryopreservation of Clitoria ternatea using an encapsulation-dehydration technique.

MATERIALS AND METHODS

An in vitro culture system via axillary shoot proliferation was developed using nodal segments in MS medium and optimization of the levels of cytokinins and auxins. Calcium alginate encapsulated axillary buds were subjected to 0-5 h of dehydration, to determine the optimum drying time and moisture content for effective cryopreservation.

RESULTS

The beads dehydrated for 4 h to 20.1 % moisture content had 60 % survival after freezing in LN, of which 65 % regrew. Based on RAPD analysis, the plants regrowing after cryostorage were genetically stable.

CONCLUSION

A simple and efficient cryopreservation protocol has been established for C. ternatea using an encapsulation-dehydration technique, and this could be effectively utilized for germplasm conservation of this species.

Adhesion-related proteins E-cadherin, P-cadherin, CD44, and CD44v6, and antimetastatic protein nm23H1 in complete hydatidiform moles in relation to invasion potential

Cell adhesion has an essential role in regulating metastasis, and loss of cell adhesion is a classic feature of invasion. There is currently a great deal of interest in the role of adhesion proteins and the antimetastatic protein nm23H1 in the progression of cancer. However, reports on the expression of these proteins in complete hydatidiform moles (CHMs) are limited. In the present study, expression of the adhesion molecules E-cadherin, P-cadherin, CD44, and CD44v6, and the antimetastatic protein nm23H1 was assessed in relation to the invasive potential of CHMs. This is the first report on the expression of these proteins in CHMs. Immunohistochemical assessment was carried out in CHMs (105 cases including 15 cases of invasive moles) and compared with that of gestational age-matched normal placentae (95 cases). The expression of the adhesion proteins ranged from mild to moderate intensity with a general down-regulation in the molar trophoblasts, the down-regulation in CD44 and CD44V6 being highly significant. No relation was, however, noticed with the invasiveness or the persistence of the disease. nm23H1 protein, on the other hand, was significantly down-regulated in the molar trophoblasts with none of the invasive lesions showing intense expression. The study thus suggests down-regulation of adhesion proteins, especially that of CD44 and CD44v6, to be an early step in the transformation to molar placenta with reduced expression of nm23H1 conferring an invasive potential to the trophoblasts.

Developmental regulation of thyrotropin receptor gene expression in the fetal and neonatal rat thyroid: relation to thyroid morphology and to thyroid-specific gene expression

The TSH receptor plays a pivotal role in thyroid gland function, growth, and differentiation, but little is known about its role or regulation in the fetus and neonate. To explore these questions, we systematically evaluated TSH receptor gene expression at the level of messenger RNA (mRNA) in thyroid glands obtained from rat fetuses and neonates, from 14 days gestation to day 5 of postnatal life. Results were compared with histological evidence of differentiation and to thyroid-specific gene expression. Northern blot and RT-PCR analysis revealed that TSH mRNA was first detected at low levels on fetal day 15, but it increased 3- to 15-fold on fetal days 17-18. Up-regulation of TSH receptor mRNA on fetal day 17-18 was accompanied by the first appearance of colloid formation and of follicular development on morphological examination. It was also paralleled by increased expression of the thyroid-specific genes thyroglobulin (Tg) and thyroid peroxidase. Unexpectedly, TSH mRNA abundance was 2- to 3-fold higher in pregnant dams than in nonpregnant adult females or adult males. In view of the 8-day lapse between the first appearance of the thyroid diverticulum and up-regulation of TSH receptor gene expression, we conclude that pituitary TSH, acting through its receptor, plays an important role in terminal thyroid maturation, but it is not involved earlier in gestation. Similarly, these data support previous evidence that the weak thyrotropic activity of human CG could not be of significance in early fetal thyroid gland development. The increased TSH receptor mRNA on fetal day 17-18 may be attributable to up-regulation by TSH, which is first secreted into the fetal circulation at this time. The significance of the increased TSH receptor expression during pregnancy remains to be explored.

The oral administration of human thyroglobulin does not affect the incidence of lymphocytic thyroiditis in the biobreeding Worcester rat

Oral tolerization with the appropriate antigen(s) to ameliorate autoimmune diseases in humans and in experimentally induced animal models, including experimentally autoimmune thyroiditis in mice, has been reported to be efficacious. Spontaneous and iodine induced (0.05% iodine in the drinking water) lymphocytic thyroiditis (LT) occurs in the diabetes mellitus (DM)-prone BioBreeding/Worcester (BB/Wor) rat. The present study was carried out to determine whether the oral administration of human thyroglobulin (hTg) would decrease the incidence of spontaneous and iodine-induced LT in the BB/Wor rat. Low iodine content hTg or bovine serum albumin (BSA) were given orally every 2 days for six doses beginning at age 50 days to BB/W rats, half of whom also received iodine in their drinking water. No effect or orally administered hTg was observed on thyroid weight, the incidence of LT or DM, or on serum thyroglobin antibodies (TgAb), thyrotropin (TSH), thyroxine (T4), and triiodothyronine (T3) concentrations when rats were killed at 100 days of age. In a second experiment, the oral administration of iodine rich hTg or BSA every 2 days for six doses beginning at 30 days of age to iodine-treated BB/Wor rats again did not affect the high incidence of LT or DM or serum TgAb, TSH, T4, and T3 concentrations. The present study suggests that oral tolerization with hTg does not affect spontaneous or iodine-induced lymphocytic thyroiditis or serum thyroglobulin antibodies in the BB/Wor rat.

Escape from the acute Wolff-Chaikoff effect is associated with a decrease in thyroid sodium/iodide symporter messenger ribonucleic acid and protein

In 1948, Wolff and Chaikoff reported that organic binding of iodide in the thyroid was decreased when plasma iodide levels were elevated (acute Wolff-Chaikoff effect), and that adaptation or escape from the acute effect occurred in approximately 2 days, in the presence of continued high plasma iodide concentrations. We later demonstrated that the escape is attributable to a decrease in iodide transport into the thyroid, lowering the intrathyroidal iodine content below a critical inhibitory threshold and allowing organification of iodide to resume. We have now measured the rat thyroid sodium/iodide symporter (NIS) messenger RNA (mRNA) and protein levels, in response to both chronic and acute iodide excess, in an attempt to determine the mechanism responsible for the decreased iodide transport. Rats were given 0.05% NaI in their drinking water for 1 and 6 days in the chronic experiments, and a single 2000-microg dose of NaI i.p. in the acute experiments. Serum was collected for iodine and hormone measurements, and thyroids were frozen for subsequent measurement of NIS, TSH receptor, thyroid peroxidase (TPO), thyroglobulin, and cyclophilin mRNAs (by Northern blotting) as well as NIS protein (by Western blotting). Serum T4 and T3 concentrations were significantly decreased at 1 day in the chronic experiments and returned to normal at 6 days, and were unchanged in the acute experiments. Serum TSH levels were unchanged in both paradigms. Both NIS mRNA and protein were decreased at 1 and 6 days after chronic iodide ingestion. NIS mRNA was decreased at 6 and 24 h after acute iodide administration, whereas NIS protein was decreased only at 24 h. TPO mRNA was decreased at 6 days of chronic iodide ingestion and 24 h after acute iodide administration. There were no iodide-induced changes in TSH receptor and thyroglobulin mRNAs. These data suggest that iodide administration decreases both NIS mRNA and protein expression, by a mechanism that is likely to be, at least in part, transcriptional. Our findings support the hypothesis that the escape from the acute Wolff-Chaikoff effect is caused by a decrease in NIS, with a resultant decreased iodide transport into the thyroid. The observed decrease in TPO mRNA may contribute to the iodine-induced hypothyroidism that is common in patients with Hashimoto's thyroiditis.

Effects of iodine repletion on thyroid morphology in iodine and/or selenium deficient rat term fetuses, pups and mothers

It has been suggested that selenium deficiency aggravates the iodine-induced thyroid inflammation and necrosis in iodine-deficient Wistar rats and possibly in man. Studies were carried out to determine whether large amounts of iodine given to iodine-deficient pregnant Sprague-Dawley rats with or without selenium deficiency would induce inflammation and necrosis in their term fetal thyroids. Iodine deficiency was induced in the dams by a low iodine diet or perchlorate in the drinking water and iodine excess was achieved by iodinated drinking water during pregnancy or daily subcutaneous injections of iodine from days 20 to 22 of pregnancy, 1 day after perchlorate was discontinued. Studies were also carried out in 30-day-old pups whose nursing mothers were iodine-deficient (perchlorate) with or without selenium deficiency from conception onward. The administration of iodine restored the morphologic changes in the thyroid induced by iodine deficiency, irrespective of selenium status, toward normal without inflammatory changes or necrosis. Possible explanations for these unexpected findings are discussed.

The effect of recombinant human thyrotropin (rhTSH) on thyroid function in mice and rats

The vast majority of studies to determine the biological activity of recombinant human thyrotropin (rhTSH) have been carried out in the mouse. We have recently reported that 0.1 mg of rhTSH IM (one-ninth the dose given in thyroid cancer patients) given to normal subjects elicits a brisk rise in serum thyroxine (T4), triiodothyronine (T3), and thyroglobulin (Tg) concentrations. In contrast, in initial studies in the rat, a low dose of rhTSH failed to increase serum T4 or T3 concentrations. The present study was, therefore, carried out to determine the biological activity of rhTSH in euthyroid and in T3-treated, TSH-suppressed rats and mice. Doses of rhTSH based on body weight were used and resulted in similar serum human thyrotropin (hTSH) concentrations in the two species. Euthyroid and TSH-suppressed mice responded briskly to rhTSH administration. In contrast, serum T4 did not increase after rhTSH administration in euthyroid rats. In TSH-suppressed rats, the increase in serum T4 was similar to that observed in TSH suppressed mice. These observations suggest that rhTSH more readily displaces endogenous TSH from the mouse than from the rat thyroid TSH receptor, because equal responses were observed when endogenous TSH was suppressed.

Dehydroepiandrosterone sulfate does not prevent spontaneous and iodine-induced lymphocytic thyroiditis and diabetes mellitus in the BB/Wor rat

Chronic feeding of dehydroepiandrosterone (DHEA) and its sulfated metabolite, dehydroepiandrosterone sulfate (DHEAS), has previously been reported to decrease hyperglycemia, obesity, cancer, and autoantibody generation in a number of animal models and to increase muscle mass and physiological and psychological well-being in elderly humans, although these latter studies remain controversial. The present study was carried out to determine whether large amounts of DHEAS given orally would prevent the occurrence of spontaneous and iodine-induced autoimmune lymphocytic thyroiditis (LT) and/or spontaneous insulin-dependent diabetes mellitus (DM) in male and female BB/Wor rats. DHEAS was administered by gavage (44 mg/rat/day) or in the chow (133 mg/rat/day) to LT- and DM-prone rats from 30 to 120 days of life; some of these rats also received iodine in the drinking water to enhance the incidence and intensity of LT. Onset of DM requiring protamine zinc insulin and its maintenance dose were assessed. Rats were killed at 90 or 120 days of age and blood, thyroid, adrenals, pancreases, testes, and ovaries were removed. Serum glucose, DHEA, DHEAS, thyroxine (T4), tri-iodothyronine (T3) and thyrotropin (TSH) concentrations were measured in all rats in both experiments. Serum DHEAS concentrations were 10-fold higher in the rats given the steroid by gavage or in the diet compared with levels in control rats. DHEAS administered over a prolonged period of time had no significant effect on body weight, incidence and severity of DM, incidence and intensity of spontaneous and iodine-induced LT, and thyroid, pancreas and testes weights but did significantly decrease adrenal and ovarian weights. Serum T4, T3, and TSH concentrations were similar in control and DHEAS-treated rats. In conclusion, DHEAS did not prevent the occurrence of iodine-induced or spontaneous autoimmune LT or spontaneous DM in the BB/Wor rat, at variance with its reported immunosuppressive effects in other animal models.

The effect of nicotine on thyroid function in rats

Very recently, it has been reported that subclinical hypothyroidism is more severe and peripheral markers of hypothyroidism are more pronounced in women with subclinical or overt hypothyroidism who smoke. Increased concentrations of the known goitrogen thiocyanate, generated from cigarette smoke, have been the major explanation for the decreased thyroid function in these women but do not explain the reported increased peripheral markers of hypothyroidism. There are no data on the effect of the other major product of cigarettes, nicotine, on thyroid function in vivo. The present studies were therefore performed to determine the effects of large doses of nicotine infused for 7 days on thyroid function, outer-ring 5'deiodinase activity (5'D-I), and hepatic malic enzyme activity (a measure of thyroid hormone action) in euthyroid, subclinically hypothyroid (hemithyroidectomized), and L-thyroxine (L-T4)-treated thyroidectomized rats. Nicotine infusion had no effect on serum T4, triiodothyronine (T3), thyrotropin (TSH), and cholesterol concentrations, intrathyroidal metabolism of 125I, liver and kidney 5'D-I activity, and hepatic malic enzyme activity in euthyroid and subclinically hypothyroid rats. Nicotine administration also did not affect serum T3, TSH, or cholesterol concentrations, liver and kidney 5'D-I activity, and hepatic malic enzyme activity in L-T4-treated thyroidectomized rats. These studies provide strong evidence that nicotine is not responsible for the observed adverse effects of smoking on the thyroid in humans.

Site selectivity of osteoblast gene expression response to thyroid hormone localized by in situ hybridization

We have previously reported that thyroid-stimulating hormone (TSH)-suppressive doses of L-thyroxine (L-T4) decrease femoral, but not vertebral, bone mineral density (BMD) in rats. L-T4-induced decreases in BMD were associated with increased expression of genes, reflecting osteoblast activity in mRNA extracted from whole femurs but not from vertebrae. To document that this skeletal selectivity reflected altered osteoblast activity, we studied gene expression by in situ hybridization in 8-wk-old rats treated with L-T4 (20 microg x 100 g body wt(-1) x day(-1)) for 4 wk. TSH-suppressive doses of L-T4 were associated with decreased femoral (0.299 +/- 0.005 vs. 0.273 +/- 0.005 g/cm2, P < 0.01), but not vertebral (0.222 +/- 0.004 vs. 0.218 +/- 0.003 g/cm2), BMD. In situ hybridization documented that L-T4 administration for 4 wk increased expression of osteocalcin and alkaline phosphatase mRNA in femoral, but not vertebral, osteoblasts. This study demonstrates a differential gene expression response of vertebral and femoral osteoblasts to L-T4. This altered degree of gene expression markers of osteoblast activity documented by in situ hybridization may in part explain the apparent clinical differences in the effect of L-T4 on femoral and vertebral BMD.

Comparison of the effects of propylthiouracil and selenium deficiency on T3 production in the rat

Selenium deficiency and propylthiouracil (PTU) treatment both decrease hepatic type I T4 5'-deiodinase activity (5'D-I), which is considered to be an important regulator of the serum T3 derived from peripheral T4 to T3 conversion (T3 neogenesis). The effects of PTU treatment or a selenium-deficient diet on T4 and T3 kinetics were compared in thyroid-ablated rats infused with stable T4 to determine whether PTU treatment is a more potent inhibitor of T3 neogenesis than selenium deficiency and to compare the degree of inhibition of T3 production with the degree of inhibition of 5'D-I. PTU treatment and selenium deficiency (Se-) did not affect the T3 MCR (control, 46.0 +/- 2.5; PTU, 41.7 +/- 2.8; Se-, 41.1 +/- 4.0 ml/h.100 g BW), but did reduce serum T3 concentrations by 29% and 25%, respectively (control, 58.7 +/- 2.6; PTU, 41.5 +/- 1.0; Se-, 43.9 +/- 2.7 ng/dl; P < 0.01 for PTU or Se- vs. control) and the T3 production rate by 35% and 32%, respectively (control, 26.6 +/- 1.0; PTU, 17.3 +/- 2.0; Se-, 18.0 +/- 1.9 ng/h.100 g BW; P < 0.01 for PTU or Se- vs. Control). PTU treatment and selenium deficiency significantly increased serum T4 concentrations by 36% and 32%, respectively, due to a decrease in T4 MCR (control, 1.4 +/- 0.1; PTU, 1.1 +/- 0.1; Se-, 1.1 +/- 0.04 ml/h.100 g BW; P < 0.05 for PTU or Se- vs. control). Assuming that the concentration of T4 available for T3 neogenesis is proportional to the serum T4 concentration, the increase in serum T4 concentrations caused by PTU treatment or Se- would probably have proportionally increased the rate of T3 neogenesis. Based on these considerations, the apparent decrease in T3 neogenesis in the PTU-treated animals was 52%. This is less than the 79% and 67% inhibition of 5'D-I noted, respectively, in the liver and kidneys of these rats. Similarly, the apparent decrease in T3 neogenesis in the Se- rats was 48%, again less than the 85% and 64% inhibition of 5'D-I in their liver and kidneys, respectively. These studies suggest that PTU and Se- have similar effects on T3 neogenesis. The more potent effects of these treatments on liver and kidney 5'D-I activities than on T3 neogenesis suggest that the activities of these enzymes in these tissues are not the only important determinants of the serum T3 that is derived from nonthyroidal sources.

Serum iodothyronine concentrations in intestinally decontaminated rats treated with a 5'-deiodinase type I inhibitor 6-anilino-2-thiouracil

Enteric bacteria have been postulated to have a role in thyroid economy by promoting the hydrolysis of thyroid hormone conjugates of biliary origin, thus permitting the absorption and recycling of thyroxine (T4) and triiodothyronine (T3). An enterohepatic circulation of T3 might be more pronounced under conditions in which type I iodothyronine deiodinase activity (5'D-I) is inhibited, because this augments the accumulation of T3 sulfate conjugates in bile. This potential of increased gut reabsorption of T3 might explain, at least in part, the failure of serum T3 values to decrease appreciably when marked reductions in peripheral 5'D-I activity are induced by selenium deficiency or 6-anilino-2-thiouracil (ATU) administration. Thus, studies were performed to determine the effect of intestinal decontamination, in the absence and in the presence of 5'D-I inhibition, on plasma T4 and T3 concentrations. Groups of adult male rats received either enteric antibiotics or no antibiotics for 12 days and then, in half of the rats in each group, treatment for 10 days with ATU, a 5'D-I inhibitor that does not affect thyroid hormone synthesis. The activity of intestinal arylsulfatase and arylsulfotransferase, enzymes that catalyze hydrolysis of thyroid hormone conjugates, was reduced markedly by approximately 87% in rats that received antibiotics, regardless of whether or not they also received ATU. The ATU treatment markedly inhibited liver 5'D-I activity in antibiotic-treated as well as in non-antibiotic-treated rats (control = 399 +/- 32 U/mg protein (mean +/- SEM); ATU = 152 +/- 17: antibiotics = 351 +/- 29; antibiotics + ATU = 130 +/- 10; p < 0.01) and significantly increased plasma T4 and T3 sulfate (T4S, T3S) concentrations (control: T4S = 2.8 +/- 0.4 and T3S = 6.7 +/- 1.3 ng/dl; ATU: T4S = 6.2 +/- 1.4 and T3S = 10.6 +/- 2.1 ng/dl; antibiotics: T4S = 1.8 +/- 0.2 and T3S = 3.6 +/- 1.0 ng/dl; antibiotics + ATU: T4S = 6.8 +/- 0.7 and T3S = 9.7 +/- 1.8 ng/dl; p < 0.05). The ATU treatment was associated with a significant increase in plasma T4 and rT3 concentrations but did not affect plasma T3 concentrations, and intestinal decontamination did not alter these ATU-associated effects on circulating thyroid hormones. These results suggest that anaerobic enteric bacteria in the rat do not have an important role in recycling of thyroid hormones, either under normal conditions or in circumstances where 5'D-I activity is markedly reduced, and that increased gut absorption of T3 from T3S cannot explain the near-normal serum T3 values found when peripheral 5'D-I activity is markedly decreased.

Compatibility and activity of aldesleukin (recombinant interleukin-2) in presence of selected drugs during simulated Y-site administration: evaluation of three methods

The compatibility and biological activity of aldesleukin (a form of recombinant interleukin-2) in the presence of selected i.v. drugs during simulated Y-site administration was studied. Five milliliters of aldesleukin 33,800 IU/mL in 5% dextrose injection was mixed in glass test tubes with 5 mL of each of 19 i.v. drugs prepared at concentrations used in routine clinical practice. The compatibility of the combinations was assessed by visual examination and spectrophotometry at 0, 0.5, 1, and 2 hours after preparation, and bioassays were conducted to determine the activity of aldesleukin in the combinations. Lorazepam was the only drug visually incompatible with aldesleukin. All the secondary drugs were spectrophotometrically compatible with aldesleukin. However, the bioassays showed that the following drugs reduced the activity of aldesleukin: ganciclovir sodium, lorazepam, pentamidine isethionate, prochlorperazine edisylate, and promethazine hydrochloride. Thus, aldesleukin became less biologically active when combined with four drugs for which visual examination suggested compatibility and when combined with five drugs for which spectrophotometry indicated compatibility. Aldesleukin 33,800 IU/mL in 5% dextrose injection lost significant biological activity in the presence of prochlorperazine edisylate, promethazine hydrochloride, lorazepam, ganciclovir sodium, and pentamidine isethionate during simulated Y-site administration. Visual assessment and spectrophotometry may not be valid methods for assessing possible changes in the biological activity of aldesleukin when combined with other agents.

Suppression of thyrotropin-releasing hormone gene expression by interleukin-1-beta in the rat: implications for nonthyroidal illness

Nonthyroidal illness is characterized by low thyroid hormone levels and inappropriately normal or decreased TSH levels. To determine whether the hypothalamus contributes to these responses, TRH gene expression in hypophysiotropic neurons of the paraventricular nucleus (PVN) was investigated using semiquantitative in situ hybridization histochemistry in an animal model of nonthyroidal illness. Following the systemic administration of bacterial lipopolysaccharide (LPS; 250 micrograms/100 g BW), plasma T4, T3 and TSH were reduced but this was not associated with an increase in the content of proTRH mRNA in the PVN as occurs when plasma T4 and T3 concentrations fall during primary hypothyroidism. Constant infusion of human interleukin-1 beta (IL-1 beta) into the cerebrospinal fluid also reduced plasma T4 concentration. This persisted for the duration of the infusion but TSH was only suppressed after 7 days of infusion when body weight had declined. By 24 h, the content of proTRH mRNA in the PVN in IL-1 beta infused animals was significantly reduced from control values. These studies indicate that the peripheral administration of endotoxin or central administration of IL-1 beta in the rat is associated with a proTRH mRNA content in the PVN that may be inappropriately normal or reduced for the level of circulating thyroid hormone. We propose that the inability of hypophysiotropic neurons to induce TRH gene expression in nonthyroidal illness, when circulating thyroid hormone levels are low, is one of several factors that contributes to the inability of the anterior pituitary to increase its secretion of TSH.

The postnatal serum 3,5,3'-triiodothyronine (T3) surge in the rat is largely independent of extrathyroidal 5'-deiodination of thyroxine to T3

In the rat, selenium deficiency causes a near-complete loss of the selenoenzyme type I 5'-deiodinase (5'D-I), resulting in a marked decrease in hepatic T4 to T3 conversion. In adult rats, serum T4 concentrations are consistently increased, whereas serum T3 and rT3 concentrations are unaffected or slightly decreased and increased, respectively. In rat fetuses near term, serum T4 and rT3 concentrations are not affected by selenium deficiency. We have now studied the effect of selenium deficiency on thyroid function in the neonatal rat. Weanling female rats were fed either a selenium-supplemented or a selenium-deficient diet for 4 weeks before mating and then throughout gestation and lactation. Neonatal rats were killed at 7, 14, 21, and 28 days. Selenium deficiency was confirmed by a more than 89% decrease in liver 5'D-I activity in mothers and pups. Selenium deficiency resulted in significant increases in serum T4 concentrations in 3- and 4-week-old pups. In contrast, selenium deficiency led to a striking increase in serum rT3 concentrations. The normal postnatal serum T3 surge was not affected by selenium deficiency at any age. In 2- and 4-week-old selenium-deficient pups obtained from a second litter from the same mothers, liver 5'D-I activity was markedly decreased, but thyroid 5'D-I activity was not affected. The increased serum rT3 and, less so, T4 concentrations observed in selenium-deficient pups were associated with a significant decrease in brain 5'D-II activity in 14- and 28-day-old pups and in brown adipose tissue 5'D-II activity in 14-day-old pups. In conclusion, the present study demonstrates that the increase in serum T4 concentrations consistently observed in selenium-deficient adult rats occurs only after the second week of life. The normal physiological postnatal 12-fold increase in serum T3 concentrations observed in selenium-deficient pups despite the marked decreases in liver 5'D-I and brain and brown adipose tissue 5'D-II activities suggests that T4 to T3 conversion by peripheral tissues may not be a major source of T3 in the neonate. In contrast, the thyroid gland, whose 5'D-I activity is not affected by selenium deficiency, is probably the principal source of circulating T3 in the neonate. Finally, the early and marked increase in serum rT3 concentrations observed in selenium-deficient pups suggests that liver 5'D-I is important in rT3 deiodination.

Etidronate inhibits the thyroid hormone-induced bone loss in rats assessed by bone mineral density and messenger ribonucleic acid markers of osteoblast and osteoclast function

TSH-suppressive doses of thyroid hormone are associated with bone loss. We have previously reported that L-T4 decreases femoral, but not vertebral bone mineral density (BMD) in rats. As bisphosphonates are able to decrease bone resorption, especially in high bone turnover states, we investigated the potential effects of etidronate disodium (EHDP) on L-T4-induced bone loss in the rat model by assessing BMD and gene expression of osteoblast (osteocalcin, osteopontin, type I collagen, and alkaline phosphatase), osteoclast (tartrate-resistant acid phosphatase), and cell growth (histone) markers in the skeleton. L-T4 administered for 20 days decreased BMD in the femur, but had no effect on the lumbar spine. EHDP alone had no effect on femoral or vertebral BMD, but did prevent the L-T4-induced bone loss in the femur. L-T4 increased mRNA levels of alkaline phosphatase, tartrate-resistant acid phosphatase, and histone H4 in the femur, but not in the vertebrae. EHDP, which alone had no effect on gene expression in the femur or vertebrae, inhibited the effect of L-T4 on mRNA markers in the femur. The results demonstrate that EHDP can prevent the L-T4-induced decrease in femoral BMD in rats that is associated with the prevention of changes in mRNA markers of osteoclast and osteoblast function. EHDP and other bisphosphonate compounds may be useful in the prevention of thyroid hormone-induced bone loss in humans.

Gene expression and serum thyroxine-binding globulin are regulated by adrenal status and corticosterone in the rat

Supraphysiological doses of glucocorticoids reduce serum T4-binding globulin (TBG) concentrations when administered to human subjects. Studies were performed in rats to determine if glucocorticoid administration alters serum TBG in another species, if circulating concentrations of glucocorticoids tonically affect serum TBG concentrations, and if changes in TBG production are likely to be a cause of the glucocorticoid-induced changes in serum TBG concentrations that are observed in humans. The serum TBG-binding capacity was 14.9 +/- 2.3 nmol/liter in adrenalectomized male rats compared to 6.6 +/- 1.0 nmol/liter in intact male rats and 4.8 +/- 0.9 nmol/liter in adrenalectomized male rats that received corticosterone in a dose equal to or less than the replacement dose, as assessed by thymus weight (P < 0.01 for serum TBG in adrenalectomized vs. intact or adrenalectomized corticosterone-treated groups). Hepatic TBG mRNA content, as assessed by polymerase chain reaction amplification and expressed as a ratio of beta-actin mRNA content, was 0.10 +/- 0.03 density units in intact male rats, 0.59 +/- 0.17 density units in adrenalectomized male rats, and 0.05 +/- 0.02 density units in adrenalectomized corticosterone-treated male rats (P < 0.03 for adrenalectomized vs. intact or adrenalectomized corticosterone-treated rats). Adrenalectomy increased the serum TBG-binding capacity in female rats (intact female rats, 13.9 +/- 1.0 nmol/liter; adrenalectomized female rats, 39.0 +/- 6.4 nmol/liter; P < 0.01). These studies indicate that serum TBG is tonically down-regulated by adrenal glucocorticoids, because corticosterone decreases the TBG production rate, probably at the level of transcription. This effect is similar to that described for corticosterone-binding globulin, but differs from that for many proteins of the serine protease inhibitor family that are related to TBG.

Placental 5-deiodinase activity and fetal thyroid hormone economy are unaffected by selenium deficiency in the rat

In adult male rats, selenium deficiency results in a near complete loss in the selenoprotein 5'-deiodinase in the liver, resulting in decreased peripheral deiodination of thyroxine (T4) and increased serum T4 concentrations. Serum 3,5,3'-triiodothyronine concentrations are normal or slightly decreased, and serum 3,3',5'-triiodothyronine concentrations are normal or slightly increased in selenium-deficient rats. We now report the effects of selenium deficiency on maternal and fetal thyroid hormone economy and on placental 5-deiodinase activity in the rat. Weanling female rats were fed either a selenium-deficient or selenium-supplemented diet for 4 wk before mating and then throughout gestation. Rats were killed at 21 d of gestation. Selenium deficiency was confirmed by a 95 and 94% decrease in glutathione peroxidase and a 84 and 56% decrease in liver type I outer ring 5' deiodinase activity in the mother and the fetus, respectively. In contrast to the increase in circulating T4 observed in selenium-deficient male and nonpregnant female adult rats, serum T4 was not affected by selenium deficiency in pregnant rats, but there was a 3-fold increase in serum 3,3',5'-triiodothyronine concentrations associated with a 70% decrease in maternal brain type II outer ring 5' deiodinase activity. Maternal serum 3,5,3'-triiodothyronine concentrations were decreased by 21%. Placental 5-deiodinase activity was unaffected by selenium deficiency. In the fetus, serum T4, 3,3',5'-triiodothyronine, and TSH concentrations were not affected by selenium deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

The thyroid gland is a major source of circulating T3 in the rat

In rats, the respective contribution of the thyroid and peripheral tissues to the pool of T3 remains unclear. Most, if not all, of the circulating T3 produced by extrathyroidal sources is generated by 5'-deiodination of T4, catalyzed by the selenoenzyme, type I iodothyronine 5'-deiodinase (5'D-I). 5'D-I in the liver and kidney is almost completely lost in selenium deficiency, resulting in a marked decrease in T4 deiodination and an increase in circulating T4 levels. Surprisingly, circulating T3 levels are only marginally decreased by selenium deficiency. In this study, we used selenium deficiency and thyroidectomy to determine the relative contribution of thyroidal and extrathyroidal sources to the total body pool of T3. Despite maintaining normal serum T4 concentrations in thyroidectomized rats by T4 replacement, serum T3 concentrations remained 55% lower than those seen in intact rats. In intact rats, restricting selenium intake had no effect on circulating T3 concentrations. Decreasing 5'D-I activity in the liver and kidney by > 90% by restricting selenium intake resulted in a further 20% decrease in serum T3 concentrations in the thyroidectomized, T4 replaced rats, suggesting that peripheral T4 to T3 conversion in these tissues generates approximately 20% of the circulating T3 concentrations. While dietary selenium restriction markedly decreased intrahepatic selenium content (> 95%), intrathyroidal selenium content decreased by only 27%. Further, thyroid 5'D-I activity actually increased 25% in the selenium deficient rats, suggesting the continued synthesis of this selenoenzyme over selenoproteins in other tissues in selenium deficiency. These data demonstrate that the thyroid is the major source of T3 in the rat and suggest that intrathyroidal T4 to T3 conversion may account for most of the T3 released by the thyroid.

Studies of the role of water on some imine–acid complexes by means of Raman spectroscopy

The percentages of protonation were determined for a conjugated Schiff base trans, trans-2,4-heptadienylidene tert-butylamine in the presence of 3-chloropropionic acid (CPR) and dichloroacetic acid (DCA) in three solvents of different polarities. In dioxane, a solvent of low polarity, protonation is only important for the strong acid DCA (50–60%). By using solvents of higher polarities, protonation is seen to increase and is almost complete for DCA in ethanol. When water molecules are added to these systems, hydrolysis of the Schiff base, measured inside the time span of the experiments (10 min), occurs readily in dioxane, is very slow in a chloroform–dioxane mixture (9:1), and is totally absent in a mixture of ethanol–dioxane (1:9). Results indicate that water does not mediate protonation in all three sets of solvent combinations. The results are also discussed in terms of the possible role that water molecules could have in the visual and bacterial pigments.

Excessive L-thyroxine therapy decreases femoral bone mineral densities in the male rat: effect of hypogonadism and calcitonin

Excess thyroid hormone decreases bone mineral density (BMD), a potential problem in managing patients with differentiated thyroid carcinoma and nontoxic goiter who require lifelong TSH-suppressive doses of thyroid hormone. We studied the effect of thyroid hormone excess on vertebral and femoral BMD and the role of hypogonadism in modulating this effect in a rat model. The potential role of calcitonin (CT) in preventing thyroid hormone-associated bone loss was also investigated. A total of 40 male Sprague-Dawley rats were divided into four groups. Groups 1 and 2 were orchidectomized (ORX); groups 3 and 4 were sham operated (SO). Groups 1 and 3 received 20 micrograms intraperitoneal L-thyroxine (L-T4) per 100 g body weight daily for 3 weeks; groups 2 and 4 received vehicle IP. Another 40 rats were divided into four groups. Groups 1 and 2 received L-T4, and groups 1 and 3 received CT, 2.5 U per 100 g body weight, subcutaneously (SC) daily for 3 weeks. BMD of the L4 and 5 and the right femur were measured by dual-energy x-ray absorptiometry at baseline and at the end of the study. Orchidectomy decreased femoral (P < 0.05) but not lumbar BMD. The administration of excess L-T4 decreased femoral (cortical) BMD in both SO (P < 0.05) and ORX rats (P < 0.05) without affecting lumbar (trabecular) BMD. CT increased lumbar BMD in both vehicle (P < 0.001) and L-T4-treated rats (P < 0.001). However, CT did not affect femoral BMD in vehicle-treated rats and did not prevent the L-T4-induced femoral bone loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of selenium deficiency on thyroid hormone economy in rats

In selenium-deficient rats, peripheral T4 to T3 conversion is markedly decreased due to the loss of the selenoprotein, type I iodothyronine 5'-deiodinase (5'D-I). Despite the marked increase in circulating T4 that results from this loss of 5'D-I, serum T3 concentrations in selenium-deficient rats remain in the normal range. To determine the physiological mechanism(s) that maintains circulating T3 when peripheral T4 to T3 conversion is impaired, we examined the interrelationships between selenium intake and the metabolism of T3 and T4 in the rat. In euthyroid rats, selenium deficiency caused the expected loss of 5'D-I, with a 52% increase in serum T4, which paralleled an increase in the T4 biological half-life. Consistent with the prolonged t1/2 of T4, short term thyroidectomy (48 h) in selenium-deficient rats failed to decrease serum T4 concentrations to the levels observed in short term thyroidectomized, selenium-supplemented rats. Short term thyroidectomy also caused an expected 33% decrease in liver 5'D-I and a 44% increase in brain type II iodothyronine 5'-deiodinase (5'D-II) activities in selenium-supplemented rats. However, in selenium-deficient rats, short term thyroidectomy did not affect 5'D-I or 5'D-II activities. In contrast to the selenium-dependent changes in circulating T4 levels, little or no change in circulating T3 concentrations occurred. There was a 20% increase in the T3 half-life in selenium-deficient rats. The serum T3 sulfate concentration was increased, and T3 deiodination was reciprocally decreased in the selenium-deficient rats. These data suggest that increased T3 sulfate generation in selenium-deficient rats may lead to greater T3 availability through enterohepatic recycling of the iodothyronine and may explain why there are only minor changes in serum T3 concentrations in selenium-deficient rats.

Effect of in vivo administration of recombinant acidic fibroblast growth factor on thyroid function in the rat: induction of colloid goiter

We have recently demonstrated that the iv administration of 0.6-60 micrograms/kg.day of acidic fibroblast growth factor (acidic FGF) increases thyroid weight in male and female rats. Interestingly, measurement of serum TSH and thyroid hormones in rats treated with 6 micrograms/kg.day acidic FGF for 30 days revealed only a slight increase in serum T4 and reverse T3 concentrations. Since thyroid function was only examined 24 h after the 30th daily treatment, we performed a series of experiments to evaluate the effects of acidic FGF on thyroid function following single and 6 multiple injections of acidic FGF. There was a small increase in the serum TSH concentrations at 2, 4, 8, and 24 h after a single high dose iv injection of acidic FGF (60 micrograms/kg). In contrast, serum T3 concentrations were slightly decreased at 2, 4, and 8 h after acidic FGF administration. There was no effect of a single injection of acidic FGF on serum T4, reverse T3, or thyroglobulin concentrations. After 6 days of treatment, there was a 34% increase in the thyroid weights of rats treated with acidic FGF. Analysis of serum hormones revealed a slight increase in serum TSH, T3, and T4 concentrations in acidic FGF-treated rats, but no change in serum reverse T3 or thyroglobulin concentrations. There was no effect of acidic FGF administration on thyroid radioiodine uptake, the intrathyroidal metabolism of radioiodine, or the relative amounts of thyroidal thyroglobulin or peroxidase messenger RNAs, or on liver 5'-deiodinase activity. In hypophysectomized rats, with no detectable levels of serum TSH, acidic FGF failed to increase thyroid weight. These data suggest that FGFs may participate with TSH in the regulation of thyroid weight and colloid accumulation, and that autocrine or paracrine growth factors may be involved in the pathogenesis of colloid goiter.

Selenium deficiency and type II 5'-deiodinase regulation in the euthyroid and hypothyroid rat: evidence of a direct effect of thyroxine

Selenium deficiency in rats is characterized by elevated serum T4 and decreased serum T3 concentrations, and low liver type I (5'D-I) and brain type II (5'D-II) iodothyronine 5'-deiodinase activities. These findings are partially explained by the demonstration that type I 5'D is a selenoprotein; however, 5'D-II does not contain selenium. Since 5'D-II varies inversely with serum T4 concentrations, and serum T4 is elevated in selenium deficiency, the decreased cerebrocortical 5'D-II activity may be secondary to the increased serum T4 levels. To determine the mechanism(s) by which selenium influences 5'D-II activity, we examined the effects of altered selenium intake on brain 5'D-II levels and enzyme turnover in euthyroid and thyroidectomized rats. Rats were fed a selenium-supplemented or selenium-deficient diet for 5 weeks from weaning; half of the animals were also thyroidectomized 3 weeks before death. Selenium deficiency was confirmed by decreased liver and brain glutathione peroxidase activities. In euthyroid rats, selenium deficiency caused a 38% increase in serum T4, and 91% and 39% decreases in 5'D-I and 5'D-II, respectively, compared to those in selenium-supplemented rats. In the thyroidectomized hypothyroid rats, selenium deficiency caused a 60% decrease in 5'D-I, but had no effect on 5'D-II activity, fractional turnover of the enzyme, or the calculated enzyme synthesis rate. The lack of effect of selenium deficiency on 5'D-II levels in hypothyroid rats is consistent with the finding that 5'D-II is not a seleno-enzyme. Thus, the decrease in brain and pituitary 5'D-II activity in selenium-deficient euthyroid rats is due to the T4-dependent increase in the turnover of the enzyme polypeptide.

Studies of the effect of hydrogen bonding on the absorption and fluorescence spectra of all-trans-retinal at room temperature

Ultraviolet (UV)–visible and fluorescence spectra were obtained for complexes of ATR and TFA at different ratios and in four different solvents: hexane, chloroform, dichloromethane, and methanol. In the first three solvents, a large excess of TFA generates retinylic cations that absorb from 459 to 600 nm. Also, in CHCl3, Raman spectroscopy and fluorescence indicate that some aggregated species like ATR:(TFA)n, with λmax of ca. 470 nm, are present. In methanol, TFA protonates the solvent and it is CH3O+H2 which interacts with ATR so that only blue-shifted H-bonded ATR is present. From these results, it is shown that in the tautomeric equilibrium [Formula: see text], form (1) is always favored in the ground state whatever the solvent. In the excited state in hexane and in methanol, (1) is rapidly transformed into (2). In CH2Cl2 and CHCl3, this transformation is absent so that there is no energy dissipation, with the result that the retinal complexes become more unstable. Keywords: all-trans-retinal, fluorescence, H-bonds, trifluoroacetic acid, UV–vis spectroscopy.

Role of transthyretin in the transport of thyroxine from the blood to the choroid plexus, the cerebrospinal fluid, and the brain

T4 is bound to transthyretin (TTR; 75%) and albumin (Alb; 25%) in rat serum and only to TTR in cerebrospinal fluid (CSF). In addition to the liver, TTR is synthesized in large amounts in the choroid plexus and then secreted into the CSF, suggesting that serum T4 could be transported to the CSF and brain via the choroid plexus. We determined whether serum T4 bound to TTR is transported into the choroid plexus and CSF. N-Bromoacetyl-L-[125I]T4, a derivative of T4 that binds covalently to TTR, was used as the affinity label for the T4-binding site on TTR. Rats were injected with [125I]T4, acetyl-[125I]T4 covalently bound to human TTR ([125I]T4Ac.human hTTR), or acetyl-[125I]T4 covalently bound to human Alb ([125I]T4Ac.hAlb). The quantities of [125I]T4Ac.hTTR and [125I]T4Ac.hAlb present in the choroid plexus, CSF, and brain 90 min later were barely detectable. In contrast, [125I]T4 injected as the unbound form accumulated in the choroid plexus and CSF to levels 6-11 times higher than with [125I]T4Ac.hTTR (P less than 0.005). We then used a synthetic flavonoid (EMD) that competitively inhibits binding of T4 to serum TTR and transiently increases serum free T4 to determine the role of choroid plexus TTR and CSF TTR in the transport of T4 from serum to brain. Rats were given 110 microCi [125I]T4 15 min after the injection of vehicle, a low (0.3 mumol/100 g BW) or high dose of EMD (2.0 mumol/100 g BW). Rats were killed 60 min later. In serum, the percentage of [125I]T4 bound to TTR decreased and free T4 increased similarly in the low and high dose EMD-treated rats. In contrast, the percentage of [125I]T4 bound to TTR in choroid plexus and, subsequently, CSF was significantly decreased in rats given the high dose of EMD, but was not affected by the low dose of EMD, suggesting that in high doses, EMD crossed from serum to choroid plexus and CSF and occupied TTR-binding sites for T4. There was a significant decrease (P less than 0.05) in the percentage of injected [125I]T4 in the high dose vs. the low dose EMD-treated rats in total choroid plexus (61%), 1 ml CSF (94%), and 1 g cerebral cortex (46%) and cerebellum (46%).(ABSTRACT TRUNCATED AT 400 WORDS)

Iodine content of rat thyroglobulin affects its antigenicity in inducing lymphocytic thyroiditis in the BB/Wor rat

The BB/Wor rat develops spontaneous insulin dependent diabetes mellitus (DM) and lymphocytic thyroiditis (LT). We have recently demonstrated that immunization of BB/Wor rats with allogeneic thyroglobulin (Tg) induces LT at an early age. The incidence of spontaneous and Tg induced LT is extremely variable among different BB/Wor sublines. It has been shown that high iodine diet significantly increases the incidence of spontaneous lymphocytic thyroiditis (LT) and low iodine diet significantly decreases the incidence of LT in genetically predisposed BB/Wor rats. Recent studies on thyroglobulin (Tg) induced LT in chicken and mouse have shown that iodine rich Tg is far more antigenic than Tg with a low iodine content, suggesting that a high iodine diet increases the immunogenicity of Tg molecule. In order to determine whether the extent of Tg iodination would affect its immunogenicity in the BB/Wor rats, the current study was carried out. Normal iodine Tg (NTg) or low iodine Tg (LTg) was obtained from thyroids of rats that were placed on regular diet or regular diet plus 0.5% methimazole, respectively. 120 rats from the NB (highly susceptible) and BB (low susceptible) sublines were randomized in three groups. Immunization was carried out with a 1:1 emulsion of complete Freund's adjuvant (CFA) and LTg, NTg (0.6 mg/rat) or saline at 30 and 37 days of age. Since spontaneous LT rarely occurs before age 75 days, rats were sacrificed at age 65 days to specifically study Tg induced LT. Immunization with NTg induced LT in 31% of the NB rats, but not in the BB subline. LTg did not induce LT in either subline.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid alteration in circulating free thyroxine modulates pituitary type II 5' deiodinase and basal thyrotropin secretion in the rat

TSH secretion is decreased by both T4 and T3. This negative feedback control of TSH secretion has been correlated with an increase in pituitary nuclear T3 content, and it is not clear whether T4 exerts its effect directly on the thyrotroph or after its deiodination to T3. However, levels of the pituitary enzyme catalyzing T4 to T3 conversion, 5'D-II, are decreased in the presence of an increased amount of T4. Thus, it is unclear why the thyrotroph would have a mechanism for modulating the production of T3, if T3 is, in fact, the sole bioactive signal providing negative feedback inhibition. To examine this apparent paradox, we administered EMD 21388, a compound which inhibits the binding of T4 to transthyretin resulting in a rapid increase in circulating free T4 levels, to rats pretreated with radiolabeled T4 and T3. We observed increases in pituitary and liver T4 content of greater than 150%, without increases in the respective tissue T3 contents. The EMD 21388-treated rats also exhibited a 25% decrease in pituitary 5'D-II activity (103.8 +/- 15.8 fmol 125I released.mg protein-1.h-1, vs. control, 137.4 +/- 15.9, mean +/- SE), as did rats treated with sodium salicylate, another compound that inhibits T4-TTR binding (100.8 +/- 7.1). TSH levels significantly decreased 2 h after the administration of EMD 21388. These data demonstrate that despite a T4-mediated decrease in pituitary 5'D-II activity, an increase in T4 independently decreases TSH secretion.

Effect of the cardiac inotropic drug, OPC 8212, on pituitary-thyroid function in the rat

3,4-Dihydro-6-[4-(3,4-dimethoxybenzoyl)-1 piperaznyl]-2(1H)-quinolinone (OPC 8212) is a new synthetic quinolinone with potent cardiac inotropic action in man. Long term oral administration of OPC induces goiter and thyroid tumor formation in rats, associated with decreases in serum T4 and increases in serum TSH concentrations. Studies were carried out to explore the mechanisms responsible for these drug induced abnormalities. OPC 8212, administered for 1 week at doses of 500 and 2000 mg/kg.day mixed with the diet, resulted in an increase in thyroid weight, a decrease in circulating T4 and free T4 concentrations and an increase in serum TSH concentrations. OPC decreased the 5'-deiodinase (5'-D) activity in liver homogenates and increased the 5'-D activity in pituitary homogenates, consistent with hypothyroidism. OPC 8212 did not affect thyroid iodine metabolism and hormone synthesis or the binding of T4 to serum binding proteins. The hepatic uptake of 125 I-T4 4 h after T4 administration was significantly increased in OPC 8212 treated rats. The biliary excretion of administered 125 I-T4 was increased in OPC 8212-treated rats and most of the increase was due to an increase in the excretion of T4-glucuronide. Hepatic T4-glucuronyltransferase activity measured in vitro in OPC 8212 treated rats was increased as compared to that of controls. It is concluded that the effect of OPC 8212 on lowering serum T4 with a compensatory rise in TSH leading to goiter formation is due to a drug-induced increase in hepatic T4 disposal. The induction of T4-glucuronyl-transferase appears to play an important role in the increased biliary excretion of T4 in OPC 8212-treated rats.

Study of the protonation of simple Schiff bases in solvents of various polarity by means of Raman spectroscopy

In this study, the protonation of simple Schiff bases by organic acids in various solvents is investigated by Raman spectroscopy and the spectral response of the C=N+ stretching mode is correlated with the macroscopic properties of the medium surrounding the imine. Upon protonation, the unperturbed C=N stretch increases in frequency due to the combination of the coupling with the C=N+H bend and a partial rehybridization of the C=N bond. Depending on the proton location relative to that of its counterion, one mechanism may prevail over the other. Intensity measurements show that protonation is mostly controlled by the hydrogen bonding properties of the solvent and by the polarity of the medium. However, whatever the solvent, full proton transfer cannot be achieved with organic acids with pKa similar to the COOH of amino acids found in visual or bacterial pigments, meaning that the protonation mechanism may depend upon particular properties of the protein. Key words: imines, protonation, Raman spectroscopy, rhodopsin, Schiff base.

Variable prevalence of lymphocytic thyroiditis among diabetes-prone sublines of BB/W or rats

The BB/Wor rat develops spontaneous autoimmune insulin-dependent diabetes mellitus (DM) and lymphocytic thyroiditis (LT). Six different inbred sublines of this rat model have been selected for studying the pathogenesis of DM and, thereby, the prevalence of DM has been carefully monitored and found to be relatively constant. In contrast, we have observed a striking difference in the prevalence and intensity of LT in these six sublines, varying from 100% in NB subline rats to 4.9% in BE subline rats at 105-110 days of age. Excess iodide administration frequently increases the prevalence of LT but did not do so in the two sublines (BB and BE) with the lowest frequency of spontaneous LT. In view of this variable prevalence of LT in the different BB/Wor sublines, it is imperative that investigators studying the pathogenesis and modulation of LT in this rat model select those sublines which express a desired frequency of spontaneous LT.

Thyroglobulin induced lymphocytic thyroiditis in two sublines of BB/Wor rats

The BB/Wor rat develops spontaneous insulin dependent diabetes mellitus (DM) and lymphocytic thyroiditis (LT). We have recently demonstrated that although the incidence of spontaneous DM is relatively constant among different inbred BB/Wor sublines the incidence of LT is extremely variable. Experimental LT can be induced in some animal species by immunization with thyroglobulin (Tg). The differences in susceptibility of Tg induced LT between a high incidence LT subline (NB) and a low incidence subline (BB) were determined after immunization with Tg obtained from Wistar rat thyroids. Immunization was accomplished using 0.6 mg Tg in complete Freund's adjuvant (FA) or FA alone at 30 and 37 days. Since spontaneous LT rarely occurs before age 75 days, rats were sacrificed at age 65 days to specifically study Tg induced LT. Immunization with Tg induced LT in the NB subline but not in the BB subline. Anti-Tg antibody (Ab) titers, T4-Ab and T3-Ab were all increased in both Tg immunized sublines but were significantly higher in Tg immunized NB rats than in Tg immunized BB rats. The increase in T4-Ab or T3-Ab resulted in factitiously low serum T4 and T3 values when a single Ab technique with polyethylene glycol (PEG) precipitation was used in the RIA. There was a dissociation in the incidence of Tg induced LT and Ab production. Although Tg immunization failed to induce LT in the BB subline, anti-Tg Ab were significantly elevated as well as both T4-Ab and T3-Ab, suggesting that anti-Tg Ab titers per se are not tightly correlated with the occurrence of LT.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of thalidomide on the incidence of iodine-induced and spontaneous lymphocytic thyroiditis and spontaneous diabetes mellitus in the BB/Wor rat

Thalidomide, a derivative of glutamic acid, has immunosuppressive effects and suppresses graft-vs-host disease in the rat and following bone marrow transplantation in man. It is effectively used in the treatment of erythema nodosum leprosum and has a potential therapeutic effect in a variety of autoimmune diseases. In view of these observations, we evaluated the effect of thalidomide on the incidence of spontaneous and iodine-induced lymphocytic thyroiditis and spontaneous insulin dependent diabetes mellitus in the BB/Wor rat. Thalidomide did not suppress the incidence of lymphocytic thyroiditis and serum anti-thyroglobulin antibodies or affect the serum concentrations of T4, T3 and TSH in this rat model. Thalidomide also did not affect the incidence of insulin dependent diabetes mellitus. In contrast to preliminary studies in man and rat demonstrating efficacy in the therapy of autoimmune diseases, thalidomide did not prevent or suppress autoimmune lymphocytic thyroiditis or insulin-dependent diabetes mellitus in the BB/Wor rat.

Gender-related differences of serum thyroxine-binding proteins in the rat

Because little information is available, studies were performed to determine the relationship between gender and sex steroid status on serum T4 binding proteins in the rat. The binding capacity of serum thyroxine-binding globulin was greater in female rats than in male rats (27 +/- 1.3 vs 18.0 +/- 1.3 nmol/l, p less than 0.01) and in fasted female rats than in fasted male rats (64.4 +/- 2.6 vs 30.8 +/- 2.7 nmol/l, p less than 0.01). The binding capacity of serum transthyretin was lower in female rats than in male rats (2.1 +/- 0.1 vs 3.1 +/- 0.1 mumol/l, p less than 0.01). Neither ovariectomy or orchidectomy affected the binding capacity of serum thyroxine-binding globulin and it was not increased in ovariectomized rats treated with estrogen. Orchidectomy did not cause a decrease in the binding capacity of serum transthyretin and testosterone administration did not increase it. In contrast, ovariectomy caused an increase in the binding capacity of serum transthyretin (Intact = 2.2 +/- 0.1 vs ovariectomized = 2.8 +/- 0.1 mumol/l, p less than 0.01) and estrogen administration caused a decrease (ovariectomized = 2.8 +/- 0.1 vs ovariectomized + E2 = 1.9 +/- 0.1 mumol/l, p less than 0.05). The results indicate that the binding capacity of serum thyroxine-binding globulin is higher in female rats than in male rats but this difference is not due to differences in the secretion of gonadal hormones. The binding capacity of transthyretin is lower in female rats than in male rats. This is probably due to the higher circulating levels of estrogen in the female compared to the male.

Flavonoid administration immediately displaces thyroxine (T4) from serum transthyretin, increases serum free T4, and decreases serum thyrotropin in the rat

Naturally occurring and synthetic plant flavonoids, such as EMD 21388, are potent inhibitors of thyroid hormone 5'-deiodinase (5'-D) in vitro, but not when given in vivo, since they are tightly bound by serum transthyretin (TTR). EMD 21388 also inhibits the binding of T4 to human, dog, and rat serum TTR in vitro and when administered to rats in vivo. In the present studies the administration of EMD 21388 inhibited the binding of T4 to TTR within 3 min, resulting in a decrease in the serum T4 concentration, an increase in the percentage of serum free T4 assessed by equilibrium dialysis, and an increase in the serum total free T4 concentration. Depending upon the dose of EMD 21388 employed, the serum total free T4 concentration was either elevated for at least 60 min or transiently elevated, returning to normal values by 60 min. Although the total serum T3 concentration was decreased and the percent free T3 increased, these changes were modest, and the serum free T3 concentrations remained normal after EMD 21388 administration. The transient elevations of serum free T4 concentrations 10 and 20 min after the administration of 0.3 mumol EMD 21388/100 g BW resulted in a significant decrease in the serum TSH concentration at 60 min. These observations strongly suggest that the serum free T4 concentration and not T4 bound to serum TTR is biologically available to the pituitary to regulate TSH secretion and/or synthesis. The administration of EMD 21388, which rapidly increases the serum free T4, but not the serum free T3, concentration, will now permit studies of the effect(s) of endogenously elevated serum free T4 concentrations, rather than those after the administration of pharmacological quantities of T3 and T4, on various aspects of the biosynthesis and release of pituitary TSH.

The effect of ciamexone on lymphocytic thyroiditis and insulin-dependent diabetes mellitus in the BB/Wor rat

Previous studies have suggested that ciamexone, a 2-cyan-aziridine derivative, is a selective immunomodulatory agent with potential therapeutic application in a variety of autoimmune diseases. In the present study, the effects of ciamexone on autoimmune lymphocytic thyroiditis and diabetes mellitus were studied in the BB rat. The data suggest that, in this animal model, ciamexone does not affect the frequency of autoimmune diabetes or lymphocytic thyroiditis nor does it affect the serum TSH or T4 concentrations.

Affinity labeling of rat liver and kidney type I 5'-deiodinase. Identification of the 27-kDa substrate binding subunit

Extrathyroidal production of 3,3',5-triiodothyronine from the thyroid secretory product, thyroxine, is catalyzed by tissue-specific iodothyronine 5'-deiodinases. Type I 5'-deiodinase (5'D-I) produces greater than 75% of the T3 found in the circulation and in thyroid hormone-responsive tissues and is most abundant in rat liver and kidney. In this study, we used the bromoacetyl derivatives of T4 (N-bromoacetyl-[125I]L-thyroxine, BrAcT4) and T3 (N-bromoacetyl-[125I]3,3',5-triiodothyronine, BrAcT3) as alkylating affinity labels to identify 5'D-I-related protein(s). BrAcT4 and BrAcT3 rapidly and irreversibly inactivated 5'D-I activity in liver and kidney microsomes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of affinity labeled 5'D-I preparations showed that approximately 80% of the affinity label was incorporated into a protein with a Mr of 27,000 (p27). 5'D-I substrates and inhibitors specifically blocked affinity labeling of p27 with a rank order of potency (BrAcT4 greater than BrAcT3 greater than 3,5,3'-triiodothyronine (rT3) approximately flavone EMD 21388 greater than iodoacetate greater than N-acetyl-T4 (NAcT4) greater than N-acetyl-T3 (NAcT3] identical to that determined for inhibition of 5'-deiodination. Hyper- and hypothyroidism-induced increases and decreases in 5'D-I activity, respectively, were matched by comparable changes in the quantity of affinity labeled p27. BrAcT3 was a less effective affinity label for p27 and minor labeling of a new band with 53 kDa was observed. Molecular sieve chromatography of detergent-solubilized 5'D-I showed coincident peaks of p27 and 5'-deiodinating activity with an apparent Mr approximately 51,000. Two-dimensional gel electrophoresis showed that p27 was a single polypeptide with a pI of 6.1. Approximately 2-5 pmol of p27 were present per mg of liver microsomal protein, equal to previous estimates for 5'D-I content. Our results suggest that p27 represents the substrate binding subunit of type I 5'-deiodinase, the enzyme catalyzing the key reaction in the activation of T4 to the thyromimetically active T3.

The inhibitory effect of large doses of methimazole on iodine induced lymphocytic thyroiditis and serum anti-thyroglobulin antibody titers in BB/Wor rats

The BB/Wor rat spontaneously develops autoimmune insulin dependent diabetes mellitus and lymphocytic thyroiditis (LT). Excess iodine ingestion enhances and low iodine diet decreases the incidence of LT in this rat model but does not affect the incidence of diabetes mellitus. The administration of a low dose of methimazole (MMI; 870 ng/gm bw ip daily) from 30-90 days of age had no significant effect on thyroid function or on the incidence of iodine induced LT and serum anti-thyroglobulin (Tg) antibodies measured by an ELISA assay. A large dose of MMI (0.05% in the drinking water) induced goiter and hypothyroidism. In addition, the incidence of LT was markedly attenuated (76% vs 6%, p less than 0.001) and reduced titers of serum anti-Tg antibodies (0.59 +/- 0.1 OD vs 0.08 +/- 0.01, p less than 0.001) were observed. This inhibitory effect of MMI on the occurrence of iodine induced LT in the BB/Wor rat may be due to the lower antigenicity of the poorly iodinated Tg secondary to MMI therapy and/or to an immunosuppressant effect of MMI itself.

Rapid effects of the flavonoid EMD 21388 on serum thyroid hormone binding and thyrotropin regulation in the rat

Naturally occurring and synthetic flavonoids are potent inhibitors of thyroid hormone 5'-deiodination and binding to human serum transthyretin (TTR) in vitro. We now describe the inhibitory effect of the most potent flavonoid, 3-methyl-4',6-dihydroxy-3',5'-dibromo-flavone (EMD 21388), on the serum protein binding of T4 and T3 and subsequent alterations of pituitary-thyroid function in the rat. Eight to 10 mumol/liter EMD 21388 added to pooled rat serum completely displaced [125I]T4 or [125I]T3 binding from TTR, the major thyroid hormone-binding protein in the rat, and markedly increased the percentages of free T4 and T3, measured by equilibrium dialysis. One to 4 h after the ip administration of 2 mumol EMD 21388/100 g BW to euthyroid rats, [125I]T4 and [125I]T3 binding to TTR decreased, serum T4 and T3 concentrations decreased, and the percentages of free T4 and free T3 increased. No changes were observed in the free T4 and free T3 concentrations. Serum TSH concentrations decreased at 1 h and were very low thereafter. EMD 21388 administration did not affect the elevated serum TSH concentrations in hypothyroid rats, strongly suggesting that the flavonoid does not directly affect TSH secretion. No changes were observed in hepatic type I 5'-deiodinase in euthyroid rats and pituitary type I and type II 5'-deiodinase in euthyroid and hypothyroid rats after EMD 21388 administration. We conclude that the ip administration of EMD 21388 to euthyroid rats inhibits T4 and T3 binding to TTR, with subsequent increases in the percentages of free T4 and free T3 and decreased serum T4 and T3 concentrations. The decrease in the serum TSH concentration was possibly due to transcient increases in the serum free T4 and/or free T3 concentrations, resulting in increased pituitary thyroid hormone content.

Fasting-associated changes in serum thyrotropin in the rat are influenced by gender

Studies in the male rat have demonstrated that fasting is associated with a decrease in serum TSH concentrations. The present studies were performed to determine if gender influenced the serum TSH changes associated with fasting. In 8 of 10 experiments in male rats, serum TSH concentrations were significantly reduced in fasted compared to fed groups. In contrast, in none of the 9 experiments in female rats were serum TSH concentrations significantly reduced in the fasted groups. When all experiments were pooled, the decrease in the serum TSH concentration in the fasted rats compared to that in the fed rats was 55 +/- 4% (mean +/- SE) in males and 10 +/- 7% in females (P less than 0.001). In female rats ovariectomy did not result in a pattern in which fasting was associated with a decrease in serum TSH concentrations. Testosterone (T) was administered to male rats during fasting, but this treatment did not prevent the fasting-induced decrease in serum TSH concentrations. In gonadectomized male rats serum TSH concentrations were unchanged by fasting. However, if T was administered to gonadectomized male rats before and during fasting, serum TSH concentrations were significantly decreased in the fasted compared to the fed rats. These studies indicate that there is a sex difference in the serum TSH response to fasting in rats. The decline in serum TSH with fasting in the male rat is not mediated by a decline in serum T concentrations. Rather, T appears to maintain a process which increases the serum TSH concentration, and it is this process that is susceptible to inhibition by fasting.