Serum selenium and single-nucleotide polymorphisms in genes for selenoproteins: relationship to markers of oxidative stress in men from Auckland, New Zealand

There is controversy as to the recommended daily intake of selenium (Se), and whether current New Zealand diets are adequate in this nutrient. Various functional single-nucleotide polymorphisms (SNPs) polymorphisms may affect the efficacy of Se utilisation. These include the glutathione peroxidases GPx1 rs1050450, GPx4 rs713041, as well as selenoproteins SEPP1 rs3877899, SEL15 rs5845, SELS rs28665122 and SELS rs4965373. This cross-sectional study measured serum Se levels of 503 healthy Caucasian men in Auckland, New Zealand, between ages 20–81. The Se distribution was compared with activities of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase, and DNA damage as measured by the single cell gel electrophoresis assay, both without and with a peroxide-induced oxidative challenge. Serum Se was measured using inductively coupled plasma-dynamic reaction cell-mass spectrometry, while selenoprotein SNPs were estimated using TaqMan^® SNP genotyping assays. While antioxidant enzyme activities and DNA damage recorded after a peroxide challenge increased with increasing serum selenium, the inherent DNA damage levels in leukocytes showed no statistically significant relationship with serum selenium. However, these relationships and dietary Se requirements at the individual level were modified by several different SNPs in genes for selenoproteins. The GPx1 rs1050450 C allele was significantly associated with GPx activity. Significant correlations between serum Se level and GPX activity were seen with all genotypes except for homozygous minor allele carriers, while the GPx1 rs1050450 CT genotype showed the highest correlation. Several genotypes showed significant correlations between serum Se and TR activity with SEPP1 rs3877899 GG genotype showing the highest correlation. A significant decreasing trend in DNA damage with increasing serum Se was seen among GPx1 rs1050450 CC and GPx4 rs713041 TT genotype carriers up to a serum Se level of 116 and 149 ng/ml, respectively. In the absence of this genetic information, we would recommend a serum Se concentration in the region of 100–150 ng/ml as providing a useful compromise.     

In vitro interactions of thallium with components of the glutathione-dependent antioxidant defence system

We investigated the hypothesis that thallium (Tl) interactions with the glutathione-dependent antioxidant defence system could contribute to the oxidative stress associated with Tl toxicity. Working in vitro with reduced glutathione (GSH), glutathione reductase (GR) or glutathione peroxidase (GPx) in solution, we studied the effects of Tl⁺ and Tl³⁺ (1-25 μM) on: (a) the amount of free GSH, investigating whether the metal binds to GSH and/or oxidizes it; (b) the activity of the enzyme GR, that catalyzes GSH regeneration; and (c) the enzyme GPx, that reduces hydroperoxide at expense of GSH oxidation. We found that, while Tl⁺ had no effect on GSH concentration, Tl³⁺ oxidized it. Both cations inhibited the reduction of GSSG by GR and the diaphorase activity of this enzyme. In addition, Tl³⁺per se oxidized NADPH, the cofactor of GR. The effects of Tl on GPx activity depended on the metal charge: Tl⁺ inhibited GPx when cumene hydroperoxide (CuOOH) was the substrate, while Tl³⁺-mediated GPx inhibition occurred with both substrates. The present results show that Tl interacts with all the components of GSH/GSSG antioxidant defence system. Alterations of this protective pathway could be partially responsible for the oxidative stress associated with Tl toxicity.     

Influence of Fluoride on Rat Kidney Antioxidant System: Effects of Methionine and Vitamin E

The aim of the study has been to determine and compare the influence upon the kidney antioxidative system, exercised by administration of vitamin E, and vitamin E in combination with methionine, under conditions of oxidative stress induced by sodium fluoride. The experiment was carried out on Wistar FL rats (adult males) that, for 35 days, were administered water, NaF, NaF with vitamin E, or vitamin E with methionine (doses: 10 mg NaF/kg of body mass/24 h, 3 mg vitamin E per 10 μl per rat for 24 h, 2 mg methionine per rat for 24 h). The influence of administered sodium fluoride and antioxidants upon the antioxidative system in kidney was examined by analyzing the concentration of malondialdehyde (MDA) and the activity of the most important antioxidative enzymes (SOD, total and both its isoenzymes, GPX, GST, GR, and CAT). The studies carried out confirmed the disadvantageous effect of the administered dose of NaF upon the antixodiative system in rats (increase in the concentration MDA, decrease activity of all antioxidative enzymes). The administration of vitamin E increased the activity of studied enzymes with the exception of glutathione reductase GR; it also reduced the procesess of lipid peroxidation. It has been found that combined doses of vitamin E and methionine were most effective in inhibiting lipid peroxidation processes. The results confirmed the antioxidative properties of methionine.     

Mapping Topoisomerase Sites in Mitochondrial DNA with a Poisonous Mitochondrial Topoisomerase I (Top1mt)

Mitochondrial topoisomerase I (Top1mt) is a type IB topoisomerase present in vertebrates and exclusively targeted to mitochondria. Top1mt relaxes mitochondrial DNA (mtDNA) supercoiling by introducing transient cleavage complexes wherein the broken DNA strand swivels around the intact strand. Top1mt cleavage complexes (Top1mtcc) can be stabilized in vitro by camptothecin (CPT). However, CPT does not trap Top1mtcc efficiently in cells and is highly cytotoxic due to nuclear Top1 targeting. To map Top1mtcc on mtDNA in vivo and to overcome the limitations of CPT, we designed two substitutions (T546A and N550H) in Top1mt to stabilize Top1mtcc. We refer to the double-mutant enzyme as Top1mt*. Using retroviral transduction and ChIP-on-chip assays with Top1mt* in Top1mt knock-out murine embryonic fibroblasts, we demonstrate that Top1mt* forms high levels of cleavage complexes preferentially in the noncoding regulatory region of mtDNA, accumulating especially at the heavy strand replication origin O_H, in the ribosomal genes (12S and 16S) and at the light strand replication origin O_L. Expression of Top1mt* also caused rapid mtDNA depletion without affecting mitochondria mass, suggesting the existence of specific mitochondrial pathways for the removal of damaged mtDNA.     

Enzymatic response to cadmium by Impatiens glandulifera: A preliminary investigation

This paper aims to develop our understanding of the effect of cadmium (Cd) on Impatiens glandulifera, a recently identified potential Cd hyperaccumulator. Impatiens glandulifera plants were exposed to three concentrations of Cd (20, 60 and 90 mg/kg) and were sampled at two timepoints (one and seven days) to investigate the stress response of I. glandulifera to Cd. Cd can induce oxidative stress in plants, triggering overproduction of reactive oxygen species (ROS). The level of activity of catalase (CAT) and ascorbate peroxidase (APX), two crucial antioxidant enzymes responsible for detoxifying ROS, were found to increase in a concentration dependent manner. Though there was no change observed in the level of superoxide dismutase (SOD) activity, the activity of glutathione S-transferase (GST), involved in detoxifying and sequestering Cd, increased after exposure to Cd. Cd did not appear to impact the levels of proline and photosynthetic pigments, indicating the plants weren't stressed by the presence of Cd. These results suggest that the rapid response observed in enzyme activity aid the efficacious mitigation of the toxic effects of Cd, preventing significant physiological stress in I. glandulifera.     

小麦胞质突变型雄性不育系85EA与其保持系线粒体DNA的比较研究

８５ＥＡ是通过电子束辐照获得的胞质突变型小麦不育要用ＲＦＬＰ和ＲＡＰＤ技术对８５ＥＡ及春保持系的线粒体ＤＮＡ进行了比较研究。ＲＦＬＰ分析表明８５ＥＡ线粒体基因组中ｃｏｘⅡ基因的位置结构与保持系发生了变化；ＲＡＰＤ分析中引物ＯＰＤ－１５扩增产物在不育系和保持系间有明显差异，不育系的扩增产物比保持系多１条分子量为０．６ｋｂ的特展览 要带，用Ｔ－ｅａｓｙ ｖｅｃｔｏｒ克隆该不育系特异条带并命名为ＯＰＤ－     

Cadmium resistance in A549 cells correlates with elevated glutathione content but not antioxidant enzymatic activities

Glutathione has been implicated to function in cytoprotection against cadmium toxicity. The mechanism by which glutathione plays this role has not been well understood. Because glutathione is an important antioxidant and several studies have shown that cadmium induces oxidative stress, this study was undertaken to determine whether development of cadmium resistance is linked to enhanced antioxidant activities. A cadmium-resistant subpopulation of human lung carcinoma A549 cells, which was developed by repeatedly exposing the cells to step-wise increased cadmium concentrations, was compared to a cadmium-sensitive one. The acquired cadmium resistance resulted from neither decreased cadmium uptake nor enhanced cellular metallothionein synthesis. Glutathione content, however, was markedly elevated in the cadmium-resistant cells. In contrast, the activities of the glutathione redox cycle related enzymes, glutathione peroxidase and reductase, were unchanged. Two other antioxidant enzymes, superoxide dismutase and catalase, were also not altered. The results suggest that the development of cadmium resistance in A549 cells unlikely results from enhanced antioxidant enzyme activities, although it is associated with elevated cellular glutathione levels. In addition, measurement of the mRNA and DNA levels for γ-glutamyleysteine synthetase, the rate-limiting enzyme for glutathione biosynthesis, revealed that enhanced expression of the enzyme but not gene amplification is likely responsible for the elevation of cellular glutathione levels.     

2,4,5-T and 2,4,5-TCP induce oxidative damage in human erythrocytes: the role of glutathione

The molecular basis of the toxic properties of phenoxy herbicides in humans and animals has been insufficiently studied. In this study, damage parameters [levels of reduced glutathione (GSH) and total glutathione; activity of glutathione reductase (GR); activities of catalase (CAT) and superoxide dismutase (SOD); levels of adenine nucleotides and adenine energy charge (AEC)] were measured in human erythrocytes exposed in vitro to 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and its metabolite 2,4,5-trichlorophenol (2,4,5-TCP). Both 2,4,5-T and 2,4,5-TCP decreased the level of reduced glutathione (GSH) in erythrocytes in comparison to the control, but did not significantly change the total glutathione (2GSH + GSSG). This suggests that GSH concentration decreases concomitantly with an increase in oxidized glutathione (GSSG). 2,4,5-TCP at 100 ppm significantly decreased catalase and SOD activities. 2,4,5-T and 2,4,5-TCP did not significantly change the activity of glutathione reductase. 2,4,5-TCP decreased the level of ATP and increased the content of ADP and AMP, indicating a fall in AEC. 2,4,5-T and 2,4,5-TCP significantly changed the erythrocyte morphology. All these data are evidence of oxidative stress in erythrocytes incubated with 2,4,5-T and 2,4,5-TCP; the stress appears to be more intense in the case of 2,4,5-TCP.     

Isolation and Purification of Carp Mitochondrial DNA and Structural Analysis of Its tRNA~(Cys) Gene and the Light Strand Origin

A new method is presented with which we isolated milochondrial DNA from fresh carp liver usingdifferential centrifugation and DNase treatment that gave high yield of purified product with an easyand economical procedure. Highly distinct bands were displayed in agarose gel electrophoresls ofthe product digested with restrictlon enzymes, which were successfully used in constructingrestriction map and molecular clone of mitochondrial genes. With DNAs thus obtained, we havecloned cysteine tRNA gene (tRNA~(Cys) gene) of carp mitochondria, determined the nucleotide sequenceof it and the light strand origin, and depicted the cloverleaf secondary structure of tDNA~(Cya) and thelight strand origin. Analysis of nucleotide sequences of tRNA~(Cy) genes of 5 vertebrates has revealedunusual features of carp mitochondrial tRNA~(Cy) gene as compared with their cytoplasmic counter-parts, Altogether 36 bases were found in the light strand origin of carp mitochondriaf: 11 pairs in thestem; and 14 bases in the loop. As compared with those of other 11 vertebrate species, the sequenceof the stem is very conservative while both sequence and length of the loop are quite variable. Thestructure of the stem-loop may play an important role in light strand replication.     

The investigation and diagnosis of pathogenic mitochondrial DNA mutations in human urothelial cells

Patients with mitochondrial DNA disease are amongst the most challenging to diagnose and manage given the striking phenotypic and genetic heterogeneity, which characterise these conditions. Recently, we and others have demonstrated the m.3243A>G mutation, one of the most common mitochondrial DNA pathogenic mutations, is present at clinically relevant levels in urinary epithelium, thus providing a practical, non-invasive test for diagnosis and mutation screening. In this study we further evaluate the use of these cells in detecting the m.3243A>G mutation, other mtDNA tRNA gene point mutations including the m.8344A>G mutation and single large-scale mtDNA deletions. We observe a robust relationship between m.3243A>G levels in urothelial cells and clinically affected tissues that does not change with time. Conversely, single large-scale mtDNA deletions can be detected in urothelial cells, with higher levels present in younger patients with more severe disease, but generally mtDNA deletion levels are not representative of those seen in a clinically affected tissue. Our results have implications for the diagnosis, management and counselling of families with mtDNA disease.     

黄芩黄酮对硒性白内障晶状体抗氧化酶表达的影响

为探讨黄芩黄酮防治白内障的作用机理 ,采用半定量RT PCR方法比较正常组、白内障组和中药防治组大鼠晶状体中GSH Px、GR和Cu ZnSOD的mRNA水平 .白内障组GSH Px、GR和Cu ZnSOD的mRNA水平在 15d龄时显著高于正常 ,然后下降 ;在 2 7d和 31d龄 ,GR和Cu ZnSOD的mRNA水平下降至与正常无显著差异 ,GSH PxmRNA水平仍略高于正常 .中药防治组晶状体中 ,3种抗氧化酶的mRNA水平在各实验取样点无明显变化 ;其中 ,GR和Cu ZnSOD的mRNA水平一直与正常无显著差异 ,GSH PxmRNA水平略高于正常 .黄芩黄酮可能通过有效清除亚硒酸钠间接产生的活性氧来防止白内障的发生 ,并使亚硒酸钠对晶状体抗氧化酶表达的影响得以消除     

Founder effects and phenotypic variation in Adelges cooleyi, an insect pest introduced to the eastern United States

Introduced organisms experience founder effects including genetic bottlenecks that result in significant reductions in genetic variation. Genetic bottlenecks may constrain the evolution of phenotypic traits that facilitate success in novel habitats. We examined the effect of introduction into novel environments on genetic diversity of an insect pest, Adelges cooleyi, which was introduced into the eastern United States during the mid nineteenth century. We compared variation in mitochondrial and nuclear genomes in native and introduced samples to determine the effect of introduction on genetic variation experienced by this insect. We also measured an ecologically important phenotype, variation in host preference, in both native and introduced samples to compare variation in that trait with molecular genetic variation. To further investigate the relationship between genetic and phenotypic variation, we examined the degree to which mtDNA haplotypes provide information about host preference. Adelges cooleyi in eastern North America has significantly reduced genetic and phenotypic variation, but this low variation does not appear to have prevented persistence in a novel environment. Introduced insects appear to have retained host preference phenotypes similar to those of insects found where introductions likely originated.     

Phylogenetic Analysis of Different Breeds of Domestic Chickens in Selected Area of Peninsular Malaysia Inferred from Partial Cytochrome b Gene Information and RAPD Markers

The present investigation was carried out in an attempt to study the phylogenetic analysis of different breeds of domestic chickens in Peninsular Malaysia inferred from partial cytochrome b gene information and random amplified polymorphic DNA (RAPD) markers. Phylogenetic analysis using both neighbor-joining (NJ) and maximum parsimony (MP) methods produced three clusters that encompassed Type-I village chickens, the red jungle fowl subspecies and the Japanese Chunky broilers. The phylogenetic analysis also revealed that majority of the Malaysian commercial chickens were randomly assembled with the Type-II village chickens. In RAPD assay, phylogenetic analysis using neighbor-joining produced six clusters that were completely distinguished based on the locality of chickens. High levels of genetic variations were observed among the village chickens, the commercial broilers, and between the commercial broilers and layer chickens. In this study, it was found that Type-I village chickens could be distinguished from the commercial chickens and Type-II village chickens at the position of the 27th nucleotide of the 351 bp cytochrome b gene. This study also revealed that RAPD markers were unable to differentiate the type of chickens, but it showed the effectiveness of RAPD in evaluating the genetic variation and the genetic relationships between chicken lines and populations.     

Tributyltin induces oxidative stress and neuronal injury by inhibiting glutathione S-transferase in rat organotypic hippocampal slice cultures

Tributyltin (TBT) has been used as a heat stabilizer, agricultural pesticide and antifouling agents on ships, boats and fish-farming nets; however, the neurotoxicity of TBT has recently become a concern. TBT is suggested to stimulate the generation of reactive oxygen species (ROS) inside cells. The aim of this study was to determine the mechanism of neuronal oxidative injury induced by TBT using rat organotypic hippocampal slice cultures. The treatment of rat hippocampal slices with TBT induced ROS production, lipid peroxidation and cell death. Pretreatment with antioxidants such as superoxide dismutase, catalase or trolox, suppressed the above phenomena induced by TBT, indicating that TBT elicits oxidative stress in hippocampal slices, which causes neuronal cell death. TBT dose-dependently inhibited glutathione S-transferase (GST), but not glutathione peroxidase or glutathione reductase in the cytosol of rat hippocampus. The treatment of hippocampal slices with TBT decreased the GST activity. Pretreatment with reduced glutathione attenuated the reduction of GST activity and cell death induced by TBT, indicating that the decrease in GST activity by TBT is involved in hippocampal cell death. When hippocampal slices were treated with sulforaphane, the expression and activity of GST were increased. Notably, TBT-induced oxidative stress and cell death were significantly suppressed by pretreatment with sulforaphane. These results indicate that GST inhibition could contribute, at least in part, to the neuronal cell death induced by TBT in hippocampal slices. This study is the first report to show the link between neuronal oxidative injury and the GST inhibition elicited by TBT.     

Ribonucleotide reductase subunit p53R2 regulates mitochondria homeostasis and function in KB and PC-3 cancer cells

Ribonucleotide reductase (RR) is a rate-limiting enzyme that catalyzes de novo conversion of ribonucleotide 5′-diphosphates to the corresponding 2′-deoxynucleotide, essential for DNA synthesis and replication. The mutations or knockout of RR small subunit, p53R2, results in the depletion of mitochondrial DNA (mtDNA) in human, implying that p53R2 might play a critical role for maintaining mitochondrial homeostasis. In this study, siRNA against p53R2 knockdown approach is utilized to examine the impact of p53R2 depletion on mitochondria and to derive underlying mechanism in KB and PC-3 cancer cells. Our results reveal that the p53R2 expression not only positively correlates with mtDNA content, but also partakes in the proper mitochondria function, such as ATP synthesis, cytochrome c oxidase activity and membrane potential maintenance. Furthermore, overexpression of p53R2 reduces intracellular ROS and protects the mitochondrial membrane potential against oxidative stress. Unexpectedly, knockdown of p53R2 has a modest, if any, effect on mitochondrial and total cellular dNTP pools. Taken together, our study provides functional evidence that mitochondria is one of p53R2-targeted organelles and suggests an unexpected function of p53R2, which is beyond known RR function on dNTP synthesis, in mitochondrial homeostatic control.     

Modulation of antioxidant defence system in brain of rainbow trout (Oncorhynchus mykiss) after chronic carbamazepine treatment

We investigated the effect of long-term exposure to CBZ on the antioxidant system in brain tissue of rainbow trout. Fish were exposed to sublethal concentrations of CBZ (1.0 μg/L, 0.2 mg/L or 2.0 mg/L) for 7, 21, and 42 days. Oxidative stress indices (LPO and CP) and activities of antioxidant enzymes (SOD, CAT, GPx and GR) in fish brain were measured. In addition, non-enzymatic antioxidant (GSH) was determined after 42 days exposure. Carbamazepine exposure at 0.2 mg/L led to significant increases (p < 0.05) of LPO and CP after 42 days and, at 2.0 mg/L, after 21 days. Activities of the antioxidant enzymes SOD, CAT, and GPx in CBZ-treated groups slightly increased during the first period (7 days). However, activities of all measured antioxidant enzymes were significantly inhibited (p < 0.05) at 0.2 mg/L exposure after 42 days and after 21 days at 2.0 mg/L. After 42 days, the content of GSH in fish brain was significantly lower (p < 0.05) in groups exposed to CBZ at 0.2 mg/L and 2.0 mg/L than in other groups. Prolonged exposure to CBZ resulted in excess reactive oxygen species formation, finally resulting in oxidative damage to lipids and proteins and inhibited antioxidant capacities in fish brain. In short, a low level of oxidative stress could induce the adaptive responses of antioxidant enzymes, but long-term exposure to CBZ could lead to serious oxidative damage in fish brain.     

Antioxidative enzyme and glutathione S-transferase activities in diabetic rats exposed to long-term ASA treatment

Low-dose acetylsalicylic acid (ASA) treatment is a standard therapeutic approach in diabetes mellitus for prevention of long-term vascular complications. The aim of the present work was to investigate the effect of long-term ASA administration in experimental diabetes on activities of some liver enzymes: glutathione peroxidase (GSHPx), catalase, glucose-6-phosphate dehydrogenase (G6PDH) and glutathione S-transferase (GST). Blood glucose, glycated hemoglobin, as well as plasma ALT and AST activities increased in rats with streptozotocin-induced experimental diabetes. The long-term hyperglycemia resulted in decreased activities of GSHPx (by 26%), catalase (by 34%), GST (by 38%) and G6PDH (by 27%) in diabetic animals. We did not observe increased accumulation of membrane lipid peroxidation products or altered levels of reduced glutathione in livers. The linear correlation between blood glucose and glycated hemoglobin in diabetic animals was distorted upon ASA treatment, which was likely due to a chemical competition between nonenzymatic protein glycosylation and protein acetylation. The long-term ASA administration partially reversed the decrease in GSHPx activity, but did not influence the activities of catalase and GST in diabetic rats. Otherwise, some decrease in these parameters was noted in ASA-treated nondiabetic animals. Increased ASA-induced G6PDH activity was recorded in both diabetic and nondiabetic rats. While both glycation due to diabetic hyperglycemia and ASA-mediated acetylation had very similar effects on the activities of all studied enzymes but G6PDH, we conclude that non-enzymatic modification by either glucose or ASA may be a common mechanism of the observed convergence.     

Active human erythropoietin expressed in insect cells using a baculovirus vector: A role for N-linked oligosaccharide

Biologically active recombinant human erythropoietin has been expressed at high levels in an insect cell background. Expression involved the preparation of a human erythropoietin cDNA, the transfer of this cDNA to the Autographa californica nuclear polyhedrosis virus (AcNPV) genome under the polyhedrin gene promoter, and the subsequent infection of Spodoptera frugiperda cells with recombinant AcNPV. Erythropoietin cDNA was prepared through the expression of the human erythropoietin gene in COS cells using pSV2 and the construction of a COS cell cDNA library in bacteriophage Lambda GT10. Prior to transfer to the AcNPV genome, erythropoietin cDNA isolated from this library was modified at the 3′-terminus in order to replace genomic erythropoietin for SV40 cDNA derived from pSV2. Transfer of this cDNA to AcNPV and the infection of S. frugiperda cells with cloned recombinant virus led to the secretion of erythropoietin: based on bioassay, rates of hormone secretion (over 40 U/ml per h) were 50-fold greater than observed for COS cells. The purified recombinant product possessed full biological activity (at least 200000 U/mg), but was of lower M_r (23000) than human erythropoietin produced in COS cells (30000) or purified from urine (30000 to 38000). This difference was attributed to the glycosylation of erythropoietin in S. frugiperda cells with oligosaccharides of only limited size. Further removal of N-linked oligosac-charides from this M_r 23000 hormone using N-Glycanase yielded an apo-erythropoietin (M_r 18000) which possessed substantially reduced biological activity. These results indicate that glycosylation, but not the normal processing of oligosaccharides to complex types, is required for the full hormonal activity of human erythropoietin during red cell development.     

锌胁迫对小球藻抗氧化酶和类金属硫蛋白的影响

通过对抗氧化酶活性和类金属硫蛋白的测定,考察在0、5、10、20、50和100 μmol/L Zn²⁺(氯化锌)胁迫下锌对普通海洋小球藻的生物学影响。结果表明:不同浓度Zn²⁺均能抑制小球藻的生长,当Zn²⁺浓度大于10 μmol/L时,小球藻生物量随培养时间延长而迅速下降;过氧化物歧化酶 (SOD)活性随Zn²⁺胁迫浓度的增加而增加,当Zn²⁺浓度为50 μmol/L时SOD活性达到最大,但继续增加Zn²⁺胁迫浓度反而导致SOD活性下降;而过氧化物酶 (POD)活性则随着Zn²⁺胁迫浓度的增加而降低。同时,实验发现藻细胞内有两种主要的锌结合形态,其中Zn结合类金属硫蛋白(Zn-MT-like)与兔肝金属硫蛋白(MT)的分子量相近,且随着Zn²⁺胁迫浓度的增加而出现规律性地增多。因此,藻细胞内Zn-MT-like蛋白的诱导量可作为小球藻受Zn²⁺胁迫的响应指标。