Dexamethasone effects on Na<Subscript>v</Subscript>1.6 in tooth pulp,dental nerves,and alveolar osteoclasts of adult rats

Dexamethasone causes extensive physiologic reactions including the reduction of inflammation and pain. Here, we asked whether it also affected dental or periodontal cells or dental innervation by altering voltage-gated sodium channel Na_v1.6 immunoreactivity (IR) or neural synaptophysin. Daily dexamethasone (0.2 mg/kg) given for 1 week to rats caused 12-fold increased intensity of Na_v1.6-IR in dendritic pulpal cells of normal molars and incisors compared with vehicle treatment. These cells also co-localized monocyte (ED-1) or dendritic cell (CD11b/Ox42) markers, and their location in molars expanded during dexamethasone treatment to include deeper pulp. Furthermore, dexamethasone caused a 10-fold decrease in the number of Na_v1.6-immunoreactive multinucleate osteoclasts along the alveolar bone of molar root sockets. No changes occurred for neural Na_v1.6 at axonal nodes of Ranvier, even though IR for calcitonin gene-related peptide was greatly decreased, as expected, and neural synaptophysin-IR was decreased 59% by dexamethasone. At 4 days after tooth injury, pulpal vasodilation and increased Na_v1.6-immunoreactive pulp cells were similar for all groups. Thus, dexamethasone changes dental pulp cell and alveolar osteoclast Na_v1.6-IR in normal teeth, but different mechanisms occur after tooth injury when tissue reactions were similar for dexamethasone- and vehicle-treated rats. Steroid-induced alterations of dental pain and inflammation coincide with altered exocytic capability in dental nerve fibers as shown by synaptophysin-IR and with altered pulp cell Na_v1.6-IR and osteoclast number, but not with any changes in Na_v1.6-IR for nodes of Ranvier in myelinated dental axons.     

Backbone resonance assignments of complexes of apo human calmodulin bound to IQ motif peptides of voltage-dependent sodium channels Na<Subscript>V</Subscript>1.1, Na<Subscript>V</Subscript>1.4 and Na<Subscript>V</Subscript>1.7

Human voltage-gated sodium (Na_V) channels are critical for initiating and propagating action potentials in excitable cells. Nine isoforms have different roles but similar topologies, with a pore-forming α-subunit and auxiliary transmembrane β-subunits. Na_V pathologies lead to debilitating conditions including epilepsy, chronic pain, cardiac arrhythmias, and skeletal muscle paralysis. The ubiquitous calcium sensor calmodulin (CaM) binds to an IQ motif in the C-terminal tail of the α-subunit of all Na_V isoforms, and contributes to calcium-dependent pore-gating in some channels. Previous structural studies of calcium-free (apo) CaM bound to the IQ motifs of Na_V1.2, Na_V1.5, and Na_V1.6 showed that CaM binding was mediated by the C-domain of CaM (CaM_C), while the N-domain (CaM_N) made no detectable contacts. To determine whether this domain-specific recognition mechanism is conserved in other Na_V isoforms, we used solution NMR spectroscopy to assign the backbone resonances of complexes of apo CaM bound to peptides of IQ motifs of Na_V1.1, Na_V1.4, and Na_V1.7. Analysis of chemical shift differences showed that peptide binding only perturbed resonances in CaM_C; resonances of CaM_N were identical to free CaM. Thus, CaM_C residues contribute to the interface with the IQ motif, while CaM_N is available to interact elsewhere on the channel.     

Characteristics of Omega-conotoxin GVI A and MVIIC Binding to Ca<Subscript>v</Subscript> 2.1 and Ca<Subscript>v</Subscript> 2.2 Channels Captured by Anti-Ca<Superscript>2+</Superscript> Channel Peptide Antibodies

A New Binding Method (NBM) was used to investigate the characteristics of the specific binding of ¹²⁵I-omega-conotoxin (ω-CTX) GVIA and ¹²⁵I-ω-CTX MVIIC to Ca_v2.1 and Ca_v2.2 channels captured from chick brain membranes by antibodies against B1Nt (a peptide sequence in Ca_v2.1 and Ca_v2.2 channels). The results for the NBM were as follows. (1) The ED₅₀ values for specific binding of ¹²⁵I-ω-CTX GVIA and ¹²⁵I-ω-CTX MVIIC to Ca_v2.1 and Ca_v2.2 channels were about 68 and 60 pM, respectively, and very similar to those (87 and 35 pM, respectively) to crude membranes from chick brain. (2) The specific ¹²⁵I-ω-CTX GVIA (100 pM) binding was inhibited by ω-CTX GVIA (0.5 nM), dynorphine A (Dyn), gentamicin (Gen), neomycin (Neo) and tobramicin (Tob) (100 μM each), but not by ω-agaconotoxin (Aga) IVA, calciseptine, ω-CTX SVIB, ω-CTX MVIIC (0.5 nM each), PN200-110 (PN), diltiazem (Dil) or verapamil (Ver) (100 μM each). Calmodulin (CaM) inhibited the specific binding in a dose-dependent manner (IC₅₀ value of about 100 μg protein/ml). (3) The specific ¹²⁵I-ω-CTX MVIIC (60 pM) binding was inhibited by ω-CTX MVIIC, ω-CTX GVIA, ω-CTX SVIB (0.5 nM each), Dyn, Neo and Tob (100 μM, each), but not by ω-Aga IVA, calciseptine (0.5 nM each), PN, Dil, Ver (100 μM each) or 100 μg protein/ml CaM. These results suggested that the characteristics of the specific binding of ¹²⁵I-ω-CTX GVIA and ¹²⁵I-ω-CTX MVIIC to Ca_v2.1 and Ca_v2.2 channels in the NBM were very similar to those to crude membranes from chick brain, although the IC₅₀ values for CaM and free Ca²⁺ of CaM were about 33- and 5000-fold higher, respectively, than those for the specific binding of ¹²⁵I-ω-CTX GVIA and ¹²⁵I-ω-CTX MVIIC to crude membranes.     

The mechano-gated K<Subscript>2P</Subscript> channel TREK-1

The versatility of neuronal electrical activity is largely conditioned by the expression of different structural and functional classes of K⁺ channels. More than 80 genes encoding the main K⁺ channel alpha subunits have been identified in the human genome. Alternative splicing, heteromultimeric assembly, post-translational modification and interaction with auxiliary regulatory subunits further increase the molecular and functional diversity of K⁺ channels. Mammalian two-pore domain K⁺ channels (K_2P) make up one class of K⁺ channels along with the inward rectifiers and the voltage- and/or calcium-dependent K⁺ channels. Each K_2P channel subunit is made up of four transmembrane segments and two pore-forming (P) domains, which are arranged in tandem and function as either homo- or heterodimeric channels. This novel structural arrangement is associated with unusual gating properties including “background” or “leak” K⁺ channel activity, in which the channels show constitutive activity at rest. In this review article, we will focus on the lipid-sensitive mechano-gated K_2P channel TREK-1 and will emphasize on the polymodal function of this “unconventional” K⁺ channel. EBSA Satellite meeting: Ion channels, Leeds, July 2007.     

Ultrasensitive pharmacological characterisation of the voltage-gated potassium channel K<Subscript>V</Subscript>1.3 studied by single-molecule fluorescence microscopy

The determination of pharmacologically relevant constants is crucial in order to understand the effects of compounds interacting with various membrane receptors. In this report we study a venom component of the Central American scorpion Centruroides limbatus, a short peptide termed hongotoxin(1) (HgTX(1)), which specifically binds to the voltage-gated potassium channel K(V)1.3 at a molecular stoichiometry of 1:1. A toxin analogue (HgTX(1)-A19C) was subjected to fluorescence labelling studies with Cy5. Utilising an ultrasensitive microscopic method (single-dye tracing; SDT) we were able to directly visualise HgTX(1)-A19C-Cy5 binding to the voltage-gated potassium channel K(V)1.3 on Jurkat cells at the single molecule level. For the first time, this approach allowed the determination of both the dissociation constant (K(D)) and the off-rate (k(off)) of HgTX(1)-A19C-Cy5 on living cells. In order to validate this novel approach, the data obtained with SDT were correlated to radioligand binding studies performed under identical conditions using a radioiodinated HgTX(1) analogue.     

Channel Activation Voltage Alone Is Directly Altered in an Isoform-specific Manner by Na<Subscript>v1.4</Subscript> and Na<Subscript>v1.5</Subscript> Cytoplasmic Linkers

The isoform-specific direct role of cytoplasmic loops in the gating of two voltage-gated sodium channel isoforms, the human cardiac channel (Na_v1.5; hH1) and the human adult skeletal muscle channel (Na_v1.4; hSkM1), was investigated. Comparison of biophysical characteristics was made among hSkM1, hH1, and several hSkM1/hH1 chimeras in which the putative cytoplasmic loops that join domain I to II (loop A) and domain II to III (loop B) from one isoform replaced one or both of the analogous loops from the other isoform. For all parameters measured, hSkM1 and hH1 behavior were significantly different. Comparison of hSkM1 and hH1 biophysical characteristics with the function of their respective chimeras indicate that only the half-activation voltage (V_a) is directly and differently altered by the species of cytoplasmic loop such that a channel consisting of one or both hSkM1 loops activates at smaller depolarizations, while a larger depolarization is required for activation of a channel containing one or both of the analogous hH1 loops. When either cardiac channel loop A or B is attached to hSkM1, a 6–7 mV depolarizing shift in V_a is measured, increasing to a nearly 20 mV depolarization when both cardiac-channel loops are attached. The addition of either skeletal muscle-channel loop to hH1 causes a 7 mV hyperpolarization in V_a, which increases to about 10 mV for the double loop chimera. There is no significant difference in either steady-state inactivation or in the recovery from inactivation data between hSkM1 and its chimeras and between hH1 and its chimeras. Data indicate that the cytoplasmic loops contribute directly to the magnitude of the window current, suggesting that channels containing skeletal muscle loops have three times the peak persistent channel activity compared to channels containing the cardiac loops. An electrostatic mechanism, in which surface charge differences among these loops might alter differently the voltage sensed by the gating mechanism of the channel, can not account for the observed isoform-specific effects of these loops only on channel activation voltage. In summary, although the DI-DII and DII-DIII loop structures among isoforms are not well conserved, these data indicate that only one gating parameter, V_a is affected directly and in an isoform-specific manner by these divergent loop structures, creating loop-specific window currents and percentages of persistently active channels at physiological voltages that will likely impact the excitability of the cell.     

In vitro fluorescence assay to study the folding of K<Subscript>v</Subscript> ion channels

A fluorescence assay to check the folding of potassium K_v channels expressed in vitro has been developed. For this aim, the fluorescently labeled channel blocker, recombinant agitoxin of yellow scorpion was employed. The level of expression of various K_v channels in vitro has been tested. It has been demonstrated that K_v2 channels form clusters on the cell surface, which are not associated with actin filaments. On the other hand, K_v10 channels form larger clusters, which are associated with actin, indicating the principal differences in the organization of cytoplasmic domains of K_v2 and K_v10 channels.     

Three ENU-induced neurological mutations in the pore loopof sodium channel <Emphasis Type="Italic">Scn8a</Emphasis> (Na<Subscript>v</Subscript>1.6) and a genetically linkedretinal mutation, <Emphasis Type="Italic">rd13</Emphasis>

The goal of The Jackson Laboratory Neuroscience Mutagenesis Facility is to generate mouse models of human neurological disease. We describe three new models obtained from a three-generation screen for recessive mutations. Homozygous mutant mice from lines nmf2 and nmf5 exhibit hind limb paralysis and juvenile lethality. Homozygous nmf58 mice exhibit a less severe movement disorder that includes sustained dystonic postures. The mutations were mapped to the distal region of mouse Chromosome (Chr) 15. Failure to complement a mutant allele of a positional candidate gene, Scn8a, demonstrated that the mutations are new alleles of Scn8a. Missense mutations of evolutionarily conserved residues of the sodium channel were identified in the three lines, with the predicted amino acid substitutions N1370T, I1392F, and L1404H. These residues are located within the pore loop of domain 3 of sodium channel Na_v1.6. The lethal phenotypes suggest that the new alleles encode proteins with partial or complete loss of function. Several human disorders are caused by mutation in the pore loop of domain 3 of paralogous sodium channel genes. Line nmf5 contains a second, independent mutation in the rd13 locus that causes a reduction in cell number in the outer nuclear layer of the retina. rd13 was mapped to the distal 4 Mb of Chr 15. No coding or splice site mutations were detected in Pde1b, a candidate gene for rd13. The generation of three independent Scn8a mutations among 1100 tested G3 families demonstrates that the Scn8a locus is highly susceptible to ENU mutagenesis. The new alleles of Scn8a will be valuable for analysis of sodium channel physiology and disease.(David A. Buchner and Kevin L. Seburn) These authors contributed equally.     

Changes in thermic limits and acclimation assessment for an alpine plant by chlorophyll fluorescence analysis: F<Subscript>v</Subscript>/F<Subscript>m</Subscript><Emphasis Type="Italic">vs.</Emphasis> R<Subscript>fd</Subscript>

A comparison between maximum quantum yield of PSII photochemistry (F_v/F_m) and chlorophyll fluorescence decrease ratio (R_fd) for low and high temperature resistance was assessed in a seasonal study of the acclimation in Pterocephalus lasiospermus. Analyzing the regression adjustment of both parameters and the lethal temperatures (LT₅₀), R_fd resulted in being a more sensitive indicator for low and high temperature treatments, since the thermic resistance estimated with R_fd parameter was never higher than those estimated with F_v/F_m. Furthermore, the use of F_v/F_m led to an overestimation of the acclimation phenomena, with 6ºC of a maximum difference between both parameters. Using R_fd as the indicator parameter, P. lasiospermus acclimated to low temperatures but it kept on being a sensitive species (the lowest LT₅₀ values only achieved–9.9 ± 0.3ºC). bserved (LT₅₀ around 43.5ºC). Thus, according to R_fd evaluation of the thermic threshold, this species could be in risk of damage at low temperatures in this alpine ecosystem.     

Endophytic infection modifies organic acid and mineral element accumulation by rice under Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> stress

Background and aims

Saline and alkali soils severely impact plant growth. Endophyte and plant associations are known to significantly modify plant metabolism. This study reports the effects of a type of endophyte on organic acid (OA) accumulation and ionic balance in rice under Na₂CO₃ stress.

Methods

Rice seedlings with (E+) and without (E-) endophytic infection were subjected to different levels of Na₂CO₃ stress (0, 5, 10, 15, and 20 mM) for two weeks. Organic acids and mineral elements in the leaves and roots were determined.

Results

Seedlings with endophytic infection accumulated mainly citrate and fumarate, with some malate and succinate in the leaves. In the roots, accumulation of malate and fumarate was enhanced significantly by endophytic infection, while less citrate and succinate was accumulated under Na₂CO₃ stress, which suggested that leaves and roots use different mechanisms to control OA metabolism. Endophytes reduced the total Na and Na:K ratios, but increased ST values, the percent changes of other measured nutrients, Chl content, and dry weight per plant under Na₂CO₃ stress.

Conclusions

Endophytic infection plays a key role in maintaining plant growth by improving nutrient uptake and adjusting OA accumulation under Na₂CO₃ stress. The application of endophytes can enhance the resistance of rice to salinity.

     

Insulin increases H<Subscript>2</Subscript>O<Subscript>2</Subscript>-induced pancreatic beta cell death

Insulin resistance results, in part, from impaired insulin signaling in insulin target tissues. Consequently, increased levels of insulin are necessary to control plasma glucose levels. The effects of elevated insulin levels on pancreatic beta (β) cell function, however, are unclear. In this study, we investigated the possibility that insulin may influence survival of pancreatic β cells. Studies were conducted on RINm, RINm5F and Min-6 pancreatic β-cells. Cell death was induced by treatment with H₂O₂, and was estimated by measurements of LDH levels, viability assay (Cell-Titer Blue), propidium iodide staining and FACS analysis, and mitochondrial membrane potential (JC-1). In addition, levels of cleaved caspase-3 and caspase activity were determined. Treatment with H₂O₂ increased cell death; this effect was increased by simultaneous treatment of cells with insulin. Insulin treatment alone caused a slight increase in cell death. Inhibition of caspase-3 reduced the effect of insulin to increase H₂O₂-induced cell death. Insulin increased ROS production by pancreatic β cells and increased the effect of H₂O₂. These effects were increased by inhibition of IR signaling, indicative of an effect independent of the IR cascade. We conclude that elevated levels of insulin may act to exacerbate cell death induced by H₂O₂ and, perhaps, other inducers of apoptosis.     

The ectopic F<Subscript>O</Subscript>F<Subscript>1</Subscript> ATP synthase of rat liver is modulated in acute cholestasis by the inhibitor protein IF<Subscript>1</Subscript>

Rat liver plasma membranes contain F_OF₁ complexes (ecto-F_OF₁) displaying a similar molecular weight to the mitochondrial F_OF₁ ATP synthase, as evidenced by Blue Native PAGE. Their ATPase activity was stably reduced in short-term extra-hepatic cholestasis. Immunoblotting and immunoprecipitation analyses demonstrated that the reduction in activity was not due to a decreased expression of ecto-F_OF₁ complexes, but to an increased level of an inhibitory protein, ecto-IF₁, bound to ecto-F_OF₁. Since cholestasis down regulates the hepatic uptake of HDL-cholesterol, and ecto-F_OF₁ has been shown to mediate SR-BI-independent hepatic uptake of HDL-cholesterol, these findings provide support to the hypothesis that ecto-F_OF₁ contributes to the fine control of reverse cholesterol transport, in parallel with SR-BI. No activity change of the mitochondrial F_OF₁ ATP synthase (m-F_OF₁), or any variation of its association with m-IF₁ was observed in cholestasis, indicating that ecto-IF₁ expression level is modulated independently from that of ecto-F_OF₁, m-IF₁ and m-F_OF₁.     

3,5-Diiodo-L-Thyronine increases F<Subscript>o</Subscript>F<Subscript>1</Subscript>-ATP synthase activity and cardiolipin level in liver mitochondria of hypothyroid rats

Short-term effects of 3,5-L-diiodothyronine (T₂) administration to hypothyroid rats on F_oF₁-ATP synthase activity were investigated in liver mitochondria. One hour after T₂ injection, state 4 and state 3 respiration rates were noticeably stimulated in mitochondria subsequently isolated. F_oF₁-ATP synthase activity, which was reduced in mitochondria from hypothyroid rats as compared to mitochondria from euthyroid rats, was significantly increased by T₂ administration in both the ATP-synthesis and hydrolysis direction. No change in β-subunit mRNA accumulation and protein amount of the α-β subunit of F_oF₁-ATP synthase was found, ruling out a T₂ genomic effect. In T₂-treated rats, changes in the composition of mitochondrial phospholipids were observed, cardiolipin (CL) showing the greatest alteration. In mitochondria isolated from hypothyroid rats the decrease in the amount of CL was accompanied by an increase in the level of peroxidised CL. T₂ administration to hypothyroid rats enhanced the level of CL and decreased the amount of peroxidised CL in subsequently isolated mitochondria, tending to restore the CL value to the euthyroid level. Minor T₂-induced changes in mitochondrial fatty acid composition were detected. Overall, the enhanced F_oF₁-ATP synthase activity observed following injection of T₂ to hypothyroid rats may be ascribed, at least in part, to an increased level of mitochondrial CL associated with decreased peroxidation of CL.     

Characterization of Myelin Sheath F<Subscript>o</Subscript>F<Subscript>1</Subscript>-ATP Synthase and its Regulation by IF<Subscript>1</Subscript>

F_oF₁-ATP synthase is the nanomotor responsible for most of ATP synthesis in the cell. In physiological conditions, it carries out ATP synthesis thanks to a proton gradient generated by the respiratory chain in the inner mitochondrial membrane. We previously reported that isolated myelin vesicles (IMV) contain functional F_oF₁-ATP synthase and respiratory chain complexes and are able to conduct an aerobic metabolism, to support the axonal energy demand. In this study, by biochemical assay, Western Blot (WB) analysis and immunofluorescence microscopy, we characterized the IMV F_oF₁-ATP synthase. ATP synthase activity decreased in the presence of the specific inhibitors (olygomicin, DCCD, FCCP, valynomicin/nigericin) and respiratory chain inhibitors (antimycin A, KCN), suggesting a coupling of oxygen consumption and ATP synthesis. ATPase activity was inhibited in low pH conditions. WB and microscopy analyses of both IMV and optic nerves showed that the Inhibitor of F₁ (IF₁), a small protein that binds the F₁ moiety in low pH when of oxygen supply is impaired, is expressed in myelin sheath. Data are discussed in terms of the role of IF₁ in the prevention of the reversal of ATP synthase in myelin sheath during central nervous system ischemic events. Overall, data are consistent with an energetic role of myelin sheath, and may shed light on the relationship among demyelination and axonal degeneration.     

Mitochondrial Ubiquitin Ligase MITOL Ubiquitinates Mutant SOD1 and Attenuates Mutant SOD1-induced Reactive Oxygen Species Generation

We have previously identified a novel mitochondrial ubiquitin ligase, MITOL, which is localized in the mitochondrial outer membrane and is involved in the control of mitochondrial dynamics. In this study, we examined whether MITOL eliminates misfolded proteins localized to mitochondria. Mutant superoxide dismutase1 (mSOD1), one of misfolded proteins, has been shown to localize in mitochondria and induce mitochondrial dysfunction, possibly involving in the onset and progression of amyotrophic lateral sclerosis. We found that in the mitochondria, MITOL interacted with and ubiquitinated mSOD1 but not wild-type SOD1. In vitro ubiquitination assay revealed that MITOL directly ubiquitinates mSOD1. Cycloheximide-chase assay in the Neuro2a cells indicated that MITOL overexpression promoted mSOD1 degradation and suppressed both the mitochondrial accumulation of mSOD1 and mSOD1-induced reactive oxygen species (ROS) generation. Conversely, the overexpression of MITOL CS mutant and MITOL knockdown by specific siRNAs resulted in increased accumulation of mSOD1 in mitochondria, which enhanced mSOD1-induced ROS generation and cell death. Thus, our findings indicate that MITOL plays a protective role against mitochondrial dysfunction caused by the mitochondrial accumulation of mSOD1 via the ubiquitin–proteasome pathway.     

ADP-Inhibition of H<Superscript>+</Superscript>-F<Subscript>O</Subscript>F<Subscript>1</Subscript>-ATP Synthase

H⁺-F_OF₁-ATP synthase (F-ATPase, F-type ATPase, F_OF₁ complex) catalyzes ATP synthesis from ADP and inorganic phosphate in eubacteria, mitochondria, chloroplasts, and some archaea. ATP synthesis is powered by the transmembrane proton transport driven by the proton motive force (PMF) generated by the respiratory or photosynthetic electron transport chains. When the PMF is decreased or absent, ATP synthase catalyzes the reverse reaction, working as an ATP-dependent proton pump. The ATPase activity of the enzyme is regulated by several mechanisms, of which the most conserved is the non-competitive inhibition by the MgADP complex (ADP-inhibition). When ADP binds to the catalytic site without phosphate, the enzyme may undergo conformational changes that lock bound ADP, resulting in enzyme inactivation. PMF can induce release of inhibitory ADP and reactivate ATP synthase; the threshold PMF value required for enzyme reactivation might exceed the PMF for ATP synthesis. Moreover, membrane energization increases the catalytic site affinity to phosphate, thereby reducing the probability of ADP binding without phosphate and preventing enzyme transition to the ADP-inhibited state. Besides phosphate, oxyanions (e.g., sulfite and bicarbonate), alcohols, lauryldimethylamine oxide, and a number of other detergents can weaken ADP-inhibition and increase ATPase activity of the enzyme. In this paper, we review the data on ADP-inhibition of ATP synthases from different organisms and discuss the in vivo role of this phenomenon and its relationship with other regulatory mechanisms, such as ATPase activity inhibition by subunit ε and nucleotide binding in the noncatalytic sites of the enzyme. It should be noted that in Escherichia coli enzyme, ADP-inhibition is relatively weak and rather enhanced than prevented by phosphate.     

Aflatoxins B<Subscript>1</Subscript> and M<Subscript>1</Subscript>: risks related to milk produced in Brazil

This work shows data on the occurrence of aflatoxins in milk produced in Brazil. A review of the literature on this contamination. Several studies carried out in Brazil show that levels of aflatoxin M₁ in milk are higher than the ones established by the legislation, an evidence of the lack of control and inspection of these mycotoxins. Taking into account that milk has been widely consumed as an important source of nutrients, mainly by children, it is fundamental to carry out a thorough study of the occurrence of aflatoxins and take measures to mitigate milk contamination.     

Effects of the Oral Administration of K<Subscript>2</Subscript>Cr<Subscript>2</Subscript>O<Subscript>7</Subscript> and Na<Subscript>2</Subscript>SeO<Subscript>3</Subscript> on Ca,Mg, Mn,Fe, Cu,and Zn Contents in the Heart,Liver, Spleen,and Kidney of Chickens

This study aimed to investigate the effects of selenium on the ion profiles in the heart, liver, spleen, and kidney through the oral administration of hexavalent chromium. Approximately 22.14 mg/kg b.w. K₂Cr₂O₇ was added to water to establish a chronic poisoning model. Different selenium levels (0.00, 0.31, 0.63, 1.25, 2.50, and 5.00 mg Na₂SeO₃/kg b.w.) around the safe dose were administered to the experimental group model. Ca, Mg, Mn, Fe, Cu, and Zn were detected in the organs through flame atomic absorption spectrometry after these organs were exposed to K₂Cr₂O₇ and Na₂SeO₃ for 14, 28, and 42 days. Results showed that these elements exhibited various changes. Ca contents declined in the heart, liver, and spleen. Ca contents also decreased on the 28th day and increased on the 42nd day in the kidney. Mn contents declined in the heart and spleen but increased in the kidney. Mn contents also decreased on the 28th day and increased on the 42nd day in the liver. Cu contents declined in the heart and spleen. Cu contents increased on the 28th day and decreased on the 42nd day in the liver and kidney. Zn contents declined in the heart and spleen. Zn contents increased on the 28th day and decreased on the 42nd day in the liver and kidney. Fe contents decreased in the heart and liver. Fe contents increased on the 28th day and decreased on the 42nd day in the spleen and kidney. Mg contents did not significantly change in these organs. Appropriate selenium contents enhanced Mn and Zn contents, which were declined by chromium. Conversely, appropriate selenium contents reduced Ca, Fe, and Cu contents, which were increased by chromium. In conclusion, the exposure of chickens to K₂Cr₂O₇ induced changes in different trace elements, and Na₂SeO₃ supplementation could alleviate this condition.