Atrial natriuretic peptide and thyroid hormones’ relation to plasma and heart calcium and magnesium concentrations of wistar rats exposed to cold and hot ambients

Plasma ANP (atrial natriuretic peptide), thyroid hormones, and calcium and magnesium levels as well as heart tissue calcium and magnesium concentrations were determined in male Wistar rats after exposure of 114 rats at low temperature (4°C) and 95 rats at high temperature (35–36°C) for 28 d. Plasma ANP, triiodothyronine (T₃), thyroxine (T₄), thyroid-stimulating hormone (TSH), free T₃, and free T₄ were estimated by radioimmunoassay, and plasma and heart tissue levels of Ca and Mg by flame atomic absorption spectrophotometry. Results were compared to a control group exposed at 20–22°C (76 rats). All the above parameters in control rats did not show statistically significant variations during the study. A significant increase of plasma ANP, T₃, T₄, Ca, and Mg concentrations developed during cold exposure, whereas a gradual decrease of plasma ANP, T₃, T₄, and Mg concentrations was revealed during hot exposure. A significant increase of heart tissue Mg concentrations developed during hot exposure. Results also indicate that plasma ANP and T₃ levels are proportionally related, whereas an inverse relationship exists between plasma ANP and T₃ levels and heart Mg concentrations, in both cold and hot exposed rats. In conclusion, ANP and thyroid hormones in relation to Ca and Mg play an important role in temperature adaptation.     

Serum T4, T3 and reverse T3 in ethanol fed rats.

To investigate the influence of chronic ethanol consumption on circulating thyroid hormone levels, male and female rats were given 20% ethanol as the only drinking solution daily for 8 weeks. Blood ethanol levels ranged 30–45 mg/L. In male rats serum T₄ decreased from the initial mean ± SD value of 5.2±1.4 to3.0 ±0.7 μg/dl; T₃ decreased from initial value of 97±14 to 66±11 ng/dl and rT₃ decreased from initial value of 19±9 to 10±1 ng/dl after 8 weeks of ethanol ingestion. Under similar experimental conditions, female rats showed a significant decrease in serum T₄ and rT₃ levels; however, T₃ levels decreased slightly but not significantly as compared to initial values. The results indicate adverse effect of chronic ethanol intake on serum thyroid hormone levels in rats.     

Leptin,NPY, Melatonin and Zinc Levels in Experimental Hypothyroidism and Hyperthyroidism: The Relation to Zinc

Since zinc mediates the effects of many hormones or is found in the structure of numerous hormone receptors, zinc deficiency leads to various functional impairments in the hormone balance. And also thyroid hormones have important activity on metabolism and feeding. NPY and leptin are affective on food intake and regulation of appetite. The present study is conducted to determine how zinc supplementation and deficiency affect thyroid hormones (free and total T3 and T4), melatonin, leptin, and NPY levels in thyroid dysfunction in rats. The experiment groups in the study were formed as follows: Control (C); Hypothyroidism (PTU); Hypothyroidism+Zinc (PTU+Zn); Hypothyroidism+Zinc deficient; Hyperthyroidism (H); Hyperthyroidism+Zinc (H+Zn); and Hyperthyroidism+Zinc deficient. Thyroid hormone parameters (FT₃, FT₄, TT₃, and TT₄) were found to be reduced in hypothyroidism groups and elevated in the hyperthyroidism groups. Melatonin values increased in hyperthyroidism and decreased in hypothyroidism. Leptin and NPY levels both increased in hypo- and hyperthyroidism. Zinc levels, on the other hand, decreased in hypothyroidism and increased in hyperthyroidism. Zinc supplementation, particularly when thyroid function is impaired, has been demonstrated to markedly prevent these changes.     

Effect of Selenium,Zinc, and Copper Supplementation on Blood Metabolic Profile in Male Buffalo (<Emphasis Type="Italic">Bubalus bubalis</Emphasis>) Calves

Twenty male buffalo calves (15 months, 200.2 ± 9.75) were divided into four groups of five animals in each and fed diets without (T1) or supplemented with 0.3 ppm selenium (Se) + 40 ppm zinc (Zn) (T2), 0.3 ppm Se + 40 ppm Zn + 10 ppm copper (Cu) (T3), and 40 ppm Zn + 10 ppm Cu (T4) for 120 days, during which blood samples were collected on days 0, 40, 80, and 120. Concentrations of glucose, total protein, albumin, globulin, urea, uric acid, and creatinine were similar in all the four groups. The level of different serum enzymes viz. lactate dehydrogenase, alkaline phosphatase, glutamate pyruvate transaminase, and glutamate oxaloacetate transaminase, and hormones viz. T₃, T₄, testosterone and insulin were similar (P > 0.05) among the four groups but the ratio of T₄/T₃ was reduced (P < 0.05) in the groups (T2 and T3) where selenium was supplemented at 120th day of supplementation. It was deduced that supplementation of 0.3 ppm Se and/or 10.0 ppm of Cu with 40 ppm Zn had no effect on blood metabolic profile in buffalo calves, except the ratio of T₄ and T₃ hormone which indicates that selenium plays an important role in converting T₄ hormone to T₃ which is more active form of thyroid hormone.     

Serum Thyrotropin in Graves’ Disease: A More Reliable Index of Circulating Thyroid-Stimulating Immunoglobulin Level than Thyroid Function?

ObjectiveTo assess the relationship between serum thyrotropin (thyroid-stimulating hormone or TSH) on one hand and thyroid-stimulating immunoglobulin (TSI), free thyroxine (T₄), and triiodothyronine (T₃) levels on the other in Graves’ disease, inasmuch as TSH may be suppressed in the presence of TSI because TSI may bind to the TSH receptor on the thyroid gland membrane and thus eliminate the need for circulating TSH for stimulating the thyroid gland.MethodsWe determined serum TSI levels in 37 women and 13 men with Graves’ disease, stratified into 4 groups on the basis of serum TSH levels irrespective of serum free T₄ and T₃ levels. Our reference ranges were 0.72 to 1.74 ng/dL for free T₄, 80 to 200 ng/dL for T₃, and to 4.0 μU/mL for TSH.ResultsMean serum TSI concentrations were highest (215% ± 28%) in patients with undetectable TSH levels (< 0.03 μU/mL) and lowest (103% ± 9%) in those with supernormal TSH concentrations (> 4.0 μU/mL). TSI levels were intermediate in the other study groups: 157% ± 16% in patients with subnormal though detectable TSH levels (0.03 to 0.39 μU/mL) and 125% ± 12% in those with normal TSH levels (0.4 to 4.0 μU/mL). Moreover, a progressive decline in TSI levels with increasing serum TSH concentrations was noted, along with a significant negative correlation (r = -0.45; P < 0.01) between serum TSI and TSH concentrations. Finally, relationships between free T₄ and T₃ levels on one hand and TSI or TSH levels on the other were not significant, with a considerable variability in free T₄ and T₃ levels being noted in individual study groups.ConclusionSerum TSH is frequently suppressed after treatment with antithyroid drugs or radioiodine (¹³¹I), irrespective of clinical thyroid function as expressed by increased, normal, or decreased free T₄ and T₃ concentrations. In an individual patient with Graves’ disease, the serum TSH level may be more reflective of the circulating TSI concentration than is thyroid gland function as expressed by free T₄ and T₃ concentrations and therefore may be as reliable a predictor of remission as TSI. (Endocr Pract. 2007;13:615-619)     

Plasma Zinc,Copper, and Serum Thyroid Hormones and Insulin Levels After Zinc Supplementation Followed by Placebo in Competitive Athletes

Intense physical activity is associated with biological adaptations involving hormones and trace elements. Zinc supplementation may affect plasma copper concentration, thyroid-stimulating hormone (TSH), thyroid hormones, insulin, and glucose homeostasis, but data in athletes are scarce. The aim of this study was to evaluate in competitive athletes (cyclists, n = 7, 32 ± 8 years) the effect of zinc supplementation (22 mg/day as zinc gluconate) during 30 days, and discontinuation using placebo (maltodextrin) during the following 30 days, on plasma zinc and copper concentrations, serum thyroid hormones, insulin and glucose levels, and HOMA2-IR. Compared to baseline, plasma zinc and Zn:Cu plasma ratio increased, but plasma copper decreased after zinc supplementation (day 30) and discontinuation (day 60) (p < 0.05). Zn supplementation and discontinuation had no effect on TSH, T3, and T4. Fasting serum insulin and HOMA2-IR increased (27% and 47%, respectively) on day 60 compared to baseline (p = 0.03), suggesting a delayed effect of zinc supplementation. Moreover, plasma zinc was positively associated with serum insulin (r = 0.87, p = 0.009) and HOMA2-IR (r = 0.81, p = 0.03) after zinc supplementation (day 30), indicating that supplemental zinc may impair glucose utilization in cyclists.     

Elements in erythrocytes of population with different thyroid hormone status

The contents of elements K, Ca, Fe, Cu, Zn, Se, and Rb in erythrocytes of 78 cases with different thyroid hormone status have been measured by proton-induced X-ray emission and neutron activation analysis. According to the status of thyroid hormones T₃, T₄, TSH, FT₃, and FT₄ detected by radioimmunoassay, the experiment subjects were divided into four groups (i.e., hyperthyroid, hypothyroid, critical [one of thyroid hormones was abnormal], and normal). Elements contents and hormones levels of four groups were analyzed by one-way analysis of variance and correlation using an SPSS/PC statistical package. The results showed that the Se contents of four groups were not significantly different (p<0.05). Zn content of hypothyroid group was significantly higher than those of hyperthyroid and critical groups. The Zn content of the normal group was higher than that of the hypothyroid group and lower than that of the hyperthyroid and critical groups. In the hyperthyroid group, there were significant correlations between elements contents and thyroid hormones levels (except TSH), but not between elements contents and levels of thyroid hormones. However, in the hypothyroid group, relatively strong correlations have been found between elements contents and thyroid hormones levels, especially between Zn and the T₃/T₄ ratio, and between Zn and TSH.     

Effects of Aluminum Exposure on Bone Mineral Density,Mineral, and Trace Elements in Rats

The purpose of the study was to investigate the effects of aluminum (Al) exposure on bone mineral elements, trace elements, and bone mineral density (BMD) in rats. One hundred Wistar rats were divided randomly into two groups. Experimental rats were given drinking water containing aluminum chloride (AlCl₃, 430 mg Al³⁺/L), whereas control rats were given distilled water for up to 150 days. Ten rats were sacrificed in each group every 30 days. The levels of Al, calcium (Ca), phosphorus (P), magnesium (Mg), zinc (Zn), iron (Fe), copper (Cu), manganese (Mn), selenium (Se), boron (B), and strontium (Sr) in bone and the BMD of femur were measured. Al-treated rats showed lower deposition of Ca, P, and Mg compared with control rats. Levels of trace elements (Zn, Fe, Cu, Mn, Se, B, and Sr) were significantly lower in the Al-treated group than in the control group from day 60, and the BMD of the femur metaphysis in the Al-treated group was significantly lower than in the control group on days 120 and 150. These findings indicate that long-term Al exposure reduces the levels of mineral and trace elements in bone. As a result, bone loss was induced (particularly in cancellous bone).     

Selenium,zinc, and thyroid hormones in healthy subjects

Iodothyronine 5′ deiodinase, which is mainly responsible for peripheral T₃ production, has recently been demonstrated to be a selenium (Se)-containing enzyme. The structure of nuclear thyroid hormone receptors contains Zinc (Zn) ions, crucial for the functional properties of the protein. In the elderly, reduced peripheral conversion of T₄ to T₃ with a lower T₃/T₄ ratio and overt hypothyroidism are frequently observed. We measured serum Se and RBC GSH-Px (as indices of Se status), circulating and RBC Zinc (as indices of Zn status), thyroid hormones and TSH in 109 healthy euthyroid subjects (52 women, 57 men), carefully selected to avoid abnormally low thyroid hormone levels induced by acute or chronic diseases or calorie restriction. The subjects were subdivided into three age groups. To avoid under- or malnutrition conditions, dietary records were obtained for a sample of 24 subjects, randomly selected and representative of the whole population for age and sex. Low T₃/T₄ ratios and reduced Se and RBC GSH-Px activity were observed only in the older group. A highly significant linear correlation between the T₃/T₄ ratio and indices of Se status was observed in the older group of subjects (r=0.54;p<0.002, for Se;r=0.50;p<0.002, for RBC GSH-Px). Indices of Zn status did not correlate with thyroid hormones, but RBC Zn was decreased in older as compared with younger subjects. We concluded that reduced peripheral T₄ conversion is related to impaired Se status in the elderly.     

Association of First-Trimester Thyroid Function Test Values with Thyroperoxidase Antibody Status,Smoking, and Multivitamin Use

ObjectiveTo determine first-trimester thyroid function values and associations with thyroperoxidase antibody (TPO-Ab) status, smoking, emesis, and iodine-containing multivitamin use.MethodsWe collected information by interview, questionnaire, and blood draw at the initial obstetric visit in 668 pregnant women without known thyroid disease. We compared thyroid-stimulating hormone (TSH), total thyroxine (T₄), and free T₄ index (FT₄I) values by TPO-Ab status. Multiple regression was used to identify characteristics associated with thyroid function values.ResultsThe following median (range containing 95% of the data points) thyroid function test values were obtained in 585 TPO-Ab–negative women: TSH, 1.1 mIU/L (0.04-3.6); FT₄I, 2.1 (1.5-2.9); and T₄, 9.9 μg/dL (7.0-14.0). The following median (range containing 95% of the data points) thyroid function test values were obtained in 83 TPO-Ab–positive women: TSH, 1.8 mIU/L (0.3-6.4) (P < .001); FT₄I, 2.0 (1.4-2.7) (P = .06); and T₄, 9.3 μg/dL (6.8-13.0) (P = .03) (P values denote statistically significant differences between TPO-Ab–positive and negative participants). Among TPO-Ab–negative participants, TSH level was not associated with use of iodine-containing multivitamins, smoking, or race. TSH increased 0.03 mIU/L for every year of maternal age (P = .03) and decreased by 0.3 mIU/L for every increase in parity (P < .001). T₄ decreased 0.04 μg/dL for every year of maternal age (P = .04). Mean FT₄I was 2.05 in smokers and 2.20 in nonsmokers (P < .01). There were no relationships between T₄ or FT₄I and parity, race, or iodine-containing multivitamin use.ConclusionTPO-Ab status of pregnant women should be considered when constructing trimester-specific reference ranges because elevated serum TPO-Ab levels are associated with higher TSH and lower T₄ values. (Endocr Pract. 2008;14:33-39)     

Use of tree seedlings for the phytoremediation of a municipal effluent used in dry areas of north-western India: Plant growth and nutrient uptake

Impacts of municipal effluent (ME) irrigation on soil physicochemical properties and its remediation by tree species were assessed with a view to utilize this resource in growing woodlot, controlling land degradation and improving environmental quality in suburban areas. Acacia nilotica L. (babool), Dalbergia sissoo L. (sissoo) and Eucalyptus camaldulensis seedlings planted in July 1998 were irrigated with ME at ½ PET (T₂), 1 PET (T₃), 2 PET (T₄), and with canal water at 1 PET (T₅). The control was soil without seedlings irrigated with ME at 1 PET (T₁). Application of ME increased minerals concentration from T₂ to T₄ in both soil and seedling in June 1999 and 2000. The increase in soil pH, EC, SOC was by <2.00-fold and availability of potassium (K), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) by >2-fold, NH₄–N by 10.44-fold and PO₄–P by 6.57-fold in T₄ than those in T₅ treatment in 2000. Available NH₄–N, PO₄–P, Mg and K were higher in 0–15 cm soil layer but continued irrigation and low soil carbon influenced leaching of NO₃–N, Na, Cu, Fe, Mn and Zn resulting their higher concentrations in 60–90 cm soil layer (P < 0.01). Lower soil nutrients in T₃ than in T₁ suggested soil amelioration by the planted seedlings and because of lowest concentration of most of the nutrients E. camaldlensis showed highest soil amelioration capacity. But nutrient utilization efficiency was highest in A. nilotica for K, Ca, Mg, Na, Fe, Cu and Zn, D. sissoo for N and P, and E. camaldulensis for Mn. Thus, planting tree seedlings, particularly E. camaldulensis, under ecological amelioration could in this way help in controlling land degradation and enhancing biomass and aesthetic benefits, although long-term application of effluent would lead to mineral/salt accumulation in soil and plants.     

<Emphasis Type="Italic">In Vivo</Emphasis> Evaluation of Transdermal Iodide Microemulsion for Treating Iodine Deficiency Using Sprague Dawley Rats

The objective of this study was to evaluate the transdermal efficiency of iodide microemulsion in treating iodine deficiency using rats as an animal model. Animals were fed either iodine-deficient diet (20 μg/kg iodide) or control diet (200 μg/kg iodide) over a 17-month period. At month 14, iodide microemulsion was applied topically in iodine-deficient group and physiological evaluations of thyroid gland functions were characterized by monitoring the thyroid hormones (T₃, T₄), thyroid-stimulating hormone (TSH), iodide ion excretion in urine, and the overall rat body weights in both groups. Moreover, morphological evaluations of thyroid gland before and after treatment were performed by ultrasound imaging and through histological assessment. Prior to microemulsion treatment, the levels of T₃, T₄, and TSH in iodine-deficient group were statistically significant as compared to that in the control group. The levels of T₃ and T₄ increased while TSH level decreased significantly in iodine-deficient group within the first 4 weeks of treatment. After treatment, iodide concentration in urine increased significantly. There was no statistical difference in weight between the two groups. Ultrasound imaging and histological evaluations showed evidence of hyperplasia in iodine-deficient group. Topical iodide microemulsion has shown a promising potential as a novel delivery system to treat iodine deficiency.     

Absence of A Thyroid Phenotype in Sortilin-Deficient Mice

Objective: The Vps10p family member sortilin is expressed in thyroid epithelial cells where it contributes to recycling of the thyroid hormone precursor thyroglobulin (Tg), a process that is thought to render hormone release more effective. Here we investigated the functional impact of sortilin in the thyroid gland using sortilin-deficient mice.Methods: We measured free T₄, thyroid-stimulating hormone (TSH) and Tg serum levels and studied thyroid morphology in 14 sortilin-deficient (Sort1)^-/-and 12 wildtype (WT) mice.Results: Serum free T₄ levels did not differ between Sort1^-/-and WT females but were significantly lower in Sort1^-/-males compared with WT (P = .0424). Neither serum TSH nor Tg levels differed between Sort1^-/-and WT mice, regardless of sex. On the same line, no thyroid histology differences were observed.Conclusion: Our findings seem to exclude a role of sortilin in thyroid hormone secretion, although it is possible that the absence of sortilin may result in a thyroid phenotype if combined with other molecular defects of thyroid hormone synthesis and secretion or under iodine deficiency.Abbreviations: T₄ = thyroxine Sort1 = Sortilin 1 Tg = thyroglobulin TSH = thyroid-stimulating hormone WT = wild type     

Lithium-Induced Hypothyroidism: Oxidative Stress and Osmotic Fragility Status in Rats

The present study was conducted to explore the possible effects of different doses of lithium carbonate on thyroid functions, erythrocyte oxidant–antioxidant status, and osmotic fragility. Twenty-four Wistar-type male rats were equally divided into three groups: groups I and II received 0.1 and0.2 % lithium carbonate in their drinking water, respectively, for 30 days. The rats in group III served as controls, drinking tap water without added lithium. At the end of the experimental period, the erythrocyte osmotic fragility and the levels of triiodothyronine (T₃), thyroxine (T₄), thyroid-stimulating hormone (TSH), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH) were measured in blood samples. Compared to controls, there was a statistically significant increase of TSH but decreases of the T₃ and T₄ levels in group II. Both experimental groups showed a statistically significant increase of the maximum osmotic fragility limit. The minimum osmotic fragility values of the animals in group II were statistically higher than those of controls. The standard hemolytic increment curve of both experimental groups was shifted to the right when compared to the curve obtained from the controls. Also, relative to controls, the activities of MDA and SOD were significantly higher and the GSH level lower in group II, but not so in group I. The results of the present study show that treatment with lithium carbonate may result in thyroid function abnormalities, increased oxidative damage, and possible compromise of the erythrocyte membrane integrity resulting from increased osmotic fragility.     

Impact of subchronic exposure to triclosan and/or fluoride on estrogenic activity in immature female rats: The expression pattern of calbindin‐D9k and estrogen receptor α genes

This study explored the influence of triclosan (TCS) in the absence and presence of sodium fluoride (NaF) on estrogenic activity and thyroid function of adolescent female rats. The results indicated that the individual exposure to TCS evoked a significant decline in T₃ and T₄ but the levels of estradiol, FSH, and LH were significantly elevated beside marked up regulation of calbindin‐D9k and estrogen α mRNA expression. On the other hand, the single exposure to NaF causes insignificant changes in thyroid hormones, but evoked a trend toward an increase in both estradiol and LH levels. No significant differences in the TSH level were recorded among the experimental groups. The joint exposure to TCS and NaF induced a significant improvement in thyroid and reproductive hormone levels. Overall, these findings revealed that exposure to TCS resulted in significant endocrine and reproductive alterations in immature female rats, while TCS + NaF coexposure resulted in lessening most effects.     

Inhibitory effect of aluminium on calcium absorption in small intestine of rats with different thyroid hormone status

To analyse the influence of thyroid status on the effect of aluminium (Al) upon intestinal calcium (Ca) absorption, adult male Wistar rats with experimentally altered thyroid hormones circulating levels, were orally treated (o.g.) with 0 (control), or 50 mg elemental Al (as chloride)/kg body weight (b.w.) per day, for a 14 d period. Hyper- and hypo-thyroid conditions were respectively achieved by means of administration of either sodium levothyroxine (50 μg/kg b.w. per day, o.g.) or methimazole, a thyroxine synthesis inhibitor (1 mg/kg b.w. per day, o.g.). In duodenum–jejunum segments, in vitro mucosa-to-serosa ⁴⁵Ca flux (JCa_ms) and kinetics of ⁴⁵Ca uptake in isolated enterocytes, were determined. In serum, concentrations of thyroxine (T4) and triiodothyronine (T3) were measured by chemiluminescent enzyme immunoassay. Unlike non-Al-treated rats, JCa_ms of Al-exposed rats decreased as serum levels of T4 and T3 increased, showing a significant inverse correlation in both cases (T4: r² = 0.414, P = 0.024; T3: r² = 0.443, P = 0.018). Enterocytes isolated from rats treated with Al plus thyroxine showed a reduction of both maximum Ca uptake (4.86 ± 0.44 vs. 6.85 ± 1.04 nmol Ca/mg protein, P < 0.05) and K_m (0.84 ± 0.18 vs. 1.05 ± 0.36 mM, P < 0.05) when compared to control. The observed variability in the Al effect on Ca transport with thyroid status of rats could be reflecting a negative interaction of Al with thyroid hormone action mechanisms on intestinal Ca absorption, which would take place mainly at Ca entry into enterocyte from lumen.     

Effects of increased pCO2 on zinc uptake and calcification in the tropical coral Stylophora pistillata

Zinc (Zn) is an essential element for corals. We investigated the effects of ocean acidification on zinc incorporation, photosynthesis, and gross calcification in the scleractinian coral Stylophora pistillata. Colonies were maintained at normal pH_T (8.1) and at two low-pH conditions (7.8 and 7.5) for 5 weeks. Corals were exposed to ⁶⁵Zn dissolved in seawater to assess uptake rates. After 5 weeks, corals raised at pH_T (8.1) exhibited higher ⁶⁵Zn activity in the coral tissue and skeleton, compared with corals raised at a lower pH. Photosynthesis, photosynthetic efficiency, and gross calcification, measured by ⁴⁵Ca incorporation, were however unchanged even at the lowest pH.     

Effect of supplemental palm oil on nutrient utilization,feeding economics and carcass characteristics in post-weaned Muzafarnagari lambs under feedlot condition

Thirty male post-weaned Muzafarnagari lambs, of about 3 months of age and similar body weight (18.47 ± 1.31 kg), were divided into 5 similar groups in order to observe the effect of graded levels of palm oil supplementation on growth, nutrient utilization, cost of feeding, carcass characteristics and meat quality under feedlot regimen. Lambs in different treatment groups were fed with concentrate mash supplemented with 0% (T₁), 2.5% (T₂), 5.0% (T₃), 7.5% (T₄) and 10% (T₅) palm oil and gram straw (Cicer arietinum) ad libitum. The growth trial was continued for 12 weeks. A metabolism trial of 6 days collection was conducted after 60 days of experimental feeding. After 90 days of feeding, randomly selected three animals from each group were slaughtered according to standard procedure for assessment of carcass traits and meat quality. Separated thoracic portion of Longissimus thoracis muscle from each carcass was collected for analysis of moisture, protein and fat. Accelerated growth in lambs under T₃ (P < 0.05) was observed as compared to other treatments with similar DM intake. Similarly, DM intake (kg)/kg gain was found most efficient (P < 0.01) in T₃ and least efficient in 10% palm oil supplemented T₅. Due to this, feed cost (rupees)/kg weight gain was calculated less (44.23) in T₃ than other palm oil supplemented treatments. DM, CP, Ca and P intakes were similar in all treatment groups during metabolism trial. Intake ratio of Ca and P was recorded 3.68:1.00, 3.42:1.00, 3.37:1.00, 3.69:1.00 and 3.44:1.00 in T₁ to T₅ treatments, respectively. Water intake and water intake/kg DM intake was also similar in different treatment groups. OM digestibility was significantly higher (P < 0.01) in 2.5% palm oil supplemented T₂ ration as compared to other treatments. DM, CP, EE, CF, NFE and P digestibilities were found similar among different treatment groups. TDN percentage in the feed increased from 60.16 (T₁) to 66.17 (T₅), which was mainly due gradual increase of palm oil in the diet, although the difference was non-significant. Whereas, DCP percentage in feed gradually depressed (P < 0.05) due to higher level of palm oil supplementation. Nitrogen retention (%) as percentage of N-absorbed was significantly higher (P < 0.05) in palm oil supplemented groups than control T₁, being highest in T₃ and T₄. This could be the reason for higher body weight gain in T₃ and T_4. Dressing and meat percentages (empty weight basis) ranged from 52.00 (T₄) to 55.06 (T₂) and 58.10 (T₂) to 62.27 (T₅), respectively, however, the differences were similar. Muscle fat% (DM basis) increased (P < 0.01) from 19.84 (T₁) to 28.94 (T₅) due to palm oil addition. Meat protein% (DM basis) remained unaffected due to these treatments, which ranged from 59.95 (T₁) to 70.47 (T₂). Result indicates that addition of 5% palm oil in concentrate mixture improved growth performance and feed conversion efficiency of weaned Muzafarnagari lambs keeping the quality of meat unaffected.     

Selenium Deficiency Inhibits the Conversion of Thyroidal Thyroxine (T4) to Triiodothyronine (T3) in Chicken Thyroids

Selenium (Se) influences the metabolism of thyroid hormones in mammals. However, the role of Se deficiency in the regulation of thyroid hormones in chickens is not well known. In the present study, we examined the levels of thyroidal triiodothyronine (T₃), thyroidal thyroxine (T₄), free triiodothyronine, free thyroxine (FT₄), and thyroid-stimulating hormone in the serum and the mRNA expression levels of 25 selenoproteins in chicken thyroids. Then, principal component analysis (PCA) was performed to analyze the relationships between the selenoproteins. The results indicated that Se deficiency influenced the conversion of T₄ to T₃ and induced the accumulation of T₄ and FT₄. In addition, the mRNA expression levels of the selenoproteins were generally decreased by Se deficiency. The PCA showed that eight selenoproteins (deiodinase 1 (Dio1), Dio2, Dio3, thioredoxin reductase 2 (Txnrd2), selenoprotein i (Seli), selenoprotein u (Selu), glutathione peroxidase 1 (Gpx1), and Gpx2) have similar trends, which indicated that they may play similar roles in the metabolism of thyroid hormones. The results showed that Se deficiency inhibited the conversion of T₄ to T₃ and decreased the levels of the crucial metabolic enzymes of the thyroid hormones, Dio1, Dio2, and Dio3, in chickens. In addition, the decreased selenoproteins (Dio1, Dio2, Dio3, Txnrd2, Seli, Selu, Gpx1, and Gpx2) induced by Se deficiency may indirectly limit the conversion of T₄ to T₃ in chicken thyroids. The information presented in this study is helpful to understand the role of Se in the thyroid function of chickens.     

A method for the analysis of six thyroid hormones in thyroid gland by liquid chromatography–tandem mass spectrometry

Perchlorate can competitively inhibit iodide uptake by the thyroid gland (TG) via the sodium/iodide symporter, consequently reducing the production of thyroid hormones (THs). Until recently, the effects of perchlorate on TH homeostasis are being examined through measurement of serum levels of TH, by immunoassay (IA)-based methods. IA methods are fast, but for TH analysis, they are compromised by the lack of adequate specificity. Therefore, selective and sensitive methods for the analysis of THs in TG are needed, for assessment of the effects of perchlorate on TH homeostasis. In this study, we developed a method for the analysis of six THs: l-thyroxine (T₄), 3,3′,5-triiodo-l-thyronine (T₃), 3,3′,5′-triiodo-l-thyronine (rT₃), 3,5-diiodo-l-thyronine (3,5-T₂), 3,3′-diiodo-l-thyronine (3,3′-T₂), and 3-iodo-l-thyronine (3-T₁) in TG, using liquid chromatography (LC)–tandem mass spectrometry (MS/MS). TGs used in this study were from rats that had been placed on either iodide-deficient diet or iodide-sufficient diet, and that had either been provided with perchlorate in drinking water (10 mg/kg/day) or control water. TGs were extracted by pronase digestion and then analyzed by LC–MS/MS. The instrumental calibration range for each TH ranged from 1 to 200 ng/ml and showed a high linearity (r > 0.99). The method quantification limits (LOQs) were determined to be 0.25 ng/mg TG for 3-T₁; 0.33 ng/mg TG for 3,3′- and 3,5-T₂; and 0.52 ng/mg TG for rT₃, T₃, and T₄. Rats were placed on an iodide-deficient or -sufficient diet for 2.5 months, and for the last 2 weeks of that period were provided either perchlorate (10 mg/kg/day) in drinking water or control water. Iodide deficiency and perchlorate administration both reduced TG stores of rT₃, T₃, and T₄. In iodide-deficient rats, perchlorate exacerbated the reduction in levels of THs in TG. With the advances in analytical methodology, the use of LC–MS/MS for measurement of hormone levels in TG will allow more comprehensive evaluations of the hypothalamic-pituitary–thyroid axis.