Ergovaline toxicity on Caco-2 cells as assessed by MTT,alamarBlue, and DNA assays

The exact mechanisms of fescue toxicity in animals have yet to be established, but it has been associated with an inability to thrive. Ergovaline is the major ergopeptine alkaloid associated with fungal infections of tall fescue. Gastrointestinal (GI) toxicity of ergovaline (10(-11) to 10(-4) M) was evaluated in Caco-2 cells (mimicking the GI epithelium) beginning on days 1, 8, and 18 of culture. Acute and chronic toxicity was assessed after 24 and 72 h of exposure. Treatment periods were chosen to study undifferentiated, semidifferentiated, and completely differentiated cells. Cell loss and metabolic activity were assessed by thiazolyl blue reduction (3-(4,5-dimethylthiozole-2-yl)-2,5,-biphenyl tetrazolium bromide [MTT], mitochondrial succinate dehyrdogenase activity), alamarBlue assay (cytochrome oxidase activity), and deoxyribonucleic acid (DNA) quantitation. Undifferentiated cells were sensitive to 1 x 10(-4) M ergovaline after acute exposure (from 52 to 74% of control values depending on assay). After 72 h of exposure to 1 x 10(-4) M ergovaline, in all three assays, treatment means were reduced to approximately 10% of the control means. By day 11 in culture, ergovaline toxicity to cells had decreased. With 24 h exposure, an apparent paradoxical increase in MTT was seen at some concentrations. This increase in MTT was also found in fully differentiated cells (day 21), whereas alamarBlue activity decreased. No change in DNA was found until 72 h of exposure, when DNA was reduced approximately 12% over most concentrations. These findings indicate differentiation state-dependent sensitivity of Caco-2 cells to ergovaline, potential problems of the MTT assay as an indicator of cellular toxicity, and usefulness of alamarBlue assay over DNA assay for toxicity assessment.     

Development of a modified MTT assay for screening antimonial resistant field isolates of Indian visceral leishmaniasis

The semi-automated MTT colorimetric assay has previously been applied on Leishmania promastigotes based on the ability of viable parasites to reduce the tetrazolium salt to an insoluble formazan product. As promastigotes are non-adherent, application of the MTT assay in its original form has a major drawback of a high and variable background absorbance due to incomplete removal of phenol red, a component of most media. We have accordingly optimised a modified MTT assay wherein the absorbance linearity was maintained for cells ranging from 1x10(4) to 1x10(7) being 0.04+/-0.003-2.38+/-0.04. In contrast, the original MTT assay had a narrower linearity range of 1x10(6)-1x10(7) cells, absorbances being 0.05+/-0.005-1.54+/-0.005. The modified MTT assay was effectively applied to study growth kinetics and identification of antimonial resistant field isolates. Considering the growing problem of antimonial unresponsiveness in the Indian subcontinent, this modified MTT assay is a useful tool for Leishmania research.     

Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; therefore their preparation should be conducted under an inert atmosphere. Evaluation of the anticancer activity of these complexes can be achieved by the MTT assay.The MTT assay is a colorimetric viability assay based on enzymatic reduction of the MTT molecule to formazan when it is exposed to viable cells. The outcome of the reduction is a color change of the MTT molecule. Absorbance measurements relative to a control determine the percentage of remaining viable cancer cells following their treatment with varying concentrations of a tested compound, which is translated to the compound anticancer activity and its IC₅₀ values. The MTT assay is widely common in cytotoxicity studies due to its accuracy, rapidity, and relative simplicity.Herein we present a detailed protocol for the synthesis of air sensitive metal based drugs and cell viability measurements, including preparation of the cell plates, incubation of the compounds with the cells, viability measurements using the MTT assay, and determination of IC₅₀ values.     

Highly sensitive electrochemical detection of potential cytotoxicity of CdSe/ZnS quantum dots using neural cell chip

Cell chip was recently developed as a simple and highly sensitive tool for the toxicity assessment of various kinds of chemicals or nano-materials. Here, we report newly discovered potential cytotoxic effects of CdSe/ZnS quantum dots (QDs) on intracellular redox environment of neural cancer cells at very low concentrations which can be only detected by cell chip technology. Green (2.1 nm in diameter) and red (6.3 nm in diameter) QDs capped with cysteamine (CA) or thioglycolic acid (TA) were found to be toxic at 100 μg/mL when assessed by trypan blue and differential pulse voltammetry (DPV). However, in case of concentration-dependent cytotoxicity, toxic effects of TA-capped QDs on human neural cells were only measured by DPV method when conventional MTT assay did not show toxicity of TA-capped QDs at low concentrations (1-10 μg/mL). Red-TA QDs and Green-TA QDs were found to decrease electrochemical signals from cells at 10 μg/mL and 5 μg/mL, respectively, while cell viability decreased at 100 μg/mL and 50 μg/mL when assessed by MTT assay, respectively. The relative decreases of cell viability determined by MTT assay were 15% and 11.9% when cells were treated with 5-50 μg/mL of Red-TA QDs and 5-30 μg/mL of Green-TA QDs, respectively. However, DPV signals decreased 37.5% and 39.2% at the same concentration range, respectively. This means that redox environment of cells is more sensitive than other components and can be easily affected by CdSe/ZnS QDs even at low concentrations. Thus, our proposed neural cell chip can be applied to detect potential cytotoxicity of various kinds of molecular imaging agents simply and accurately.     

Inhibitors of V-type ATPases, bafilomycin A1 and concanamycin A, protect against beta-amyloid-mediated effects on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction

The functional viability of cells can be evaluated using a number of different assay determinants. One common assay involves exposing cells to 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), which is converted intracellularly to a colored formazan precipitate and often used to assess amyloid peptide-induced cytotoxic effects. The MTT assay was employed to evaluate the role of endosomal uptake and lysosomal acidification in amyloid peptide-treated differentiated PC12 cell cultures using selective vacuolar-type (V-type) ATPase inhibitors. The macrolides bafilomycin A1 (BAF) and concanamycin A (CON) block lysosomal acidification through selective inhibition of the V-type ATPase. Treating nerve growth factor-differentiated PC12 cells with nanomolar concentrations of BAF or CON provides complete protection against the effects of beta-amyloid peptides Abeta(1-42), Abeta(1-40), and Abeta(25-35) and of amylin on MTT dye conversion. These macrolides do not inhibit peptide aggregation, act as antioxidants, or inhibit Abeta uptake by cells. Measurements of lysosomal acidification reveal that the concentrations of BAF and CON effective in reversing Abeta-mediated MTT dye conversion also reverse lysosomal pH. These results suggest that lysosomal acidification is necessary for Abeta effects on MTT dye conversion.     

Apoptosis enzyme-linked immunosorbent assay distinguishes anticancer drugs from toxic chemicals and predicts drug synergism

The effects of anticancer drugs and toxic compounds on leukemic cells in culture were evaluated by enzyme-linked-immunosorbent assay (ELISA) based on the detection of apoptotic cells by a monoclonal antibody against single-stranded DNA. The concentrations of 13 anticancer drugs, which increased apoptosis ELISA absorbance, were similar to the concentrations decreasing long-term cell survival. Short-term metabolic tetrazolium-based 3-(4,5-dimethylthiazol-yl)-2,5-diphenyformazan bromide (MTT) assay was significantly less sensitive than apoptosis ELISA and the cell survival assay. In contrast to anticancer drugs, 12 toxic chemicals did not increase apoptosis ELISA absorbance at cytotoxic concentrations. The difference between two groups of compounds by apoptosis ELISA was especially large in cultures treated with twofold of concentrations producing 50% inhibition of cell growth: all anticancer drugs induced intense reaction (mean absorbance 2.0), while none of the toxic chemicals induced apoptosis. The application of apoptosis ELISA to chemosensitivity testing was evaluated by its ability to detect synergism of anticancer drug combinations. Among 66 drug combinations tested, only combination of nitrogen mustard with mithramycin was highly synergistic by the apoptosis ELISA, as defined by apoptosis induction with the combination containing each drug at 50% of effective concentration. This combination was also synergistic in the cell survival assay, producing significant cell kill while each drug alone had no effect on cell survival. This synergism was not detected by MTT assay. We conclude that apoptosis ELISA could be useful for drug development and chemosensitivity assessment as it can distinguish clinically useful anticancer drugs from toxic compounds, is as sensitive as the long-term cell survival assay and can detect anticancer drug synergism by rapid evaluation of apoptosis induction.     

A Comparison of Colorimetric and DNA Quantification Assays for the Assessment of Meniscal Fibrochondrocyte Proliferation in Microcarrier Culture

We have developed and refined a rapid, reliable method for the evaluation of attachment and proliferation of ovine meniscal chondrocytes in microcarrier culture. Assays measuring both mitochondrial activity, using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] and MTS [3-(4,5-dimethylthiazol-2-yl)5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium], and DNA synthesis with a PicoGreen assay were compared. The MTT assay was the most sensitive at lower cell concentrations and enabled accurate assessment of cell proliferation over 14 day culture.     

A new method for antimicrobial susceptibility testing of in vitro-cultured bacteria by means of resonance light scattering technique

A new method for antimicrobial susceptibility testing of in vitro-cultured bacteria on an ordinary fluorescence spectrometer was developed. The viable bacteria reduced 3- (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to produce insoluble particles that displayed intense resonance scattering light (RSL). The assay showed a linear relationship between the number of viable bacteria and the intensity of resonance scattering light. Dead bacteria were unable to reduce MTT. Methicillin-resistant Staphylococcus aureus exposed to flavonoids from Marchantia convoluta showed a flavonoids concentration-dependent inhibition of the ability to reduce MTT. In the assay, less than 12 h were required to attain susceptibility results and fewer bacteria were utilized than in traditional methods. The RLS technique could, in combination with the MTT assay, be a rapid and sensitive measuring method to determine the in vitro activity of new antimicrobials.     

Application of the chemiluminescent assay to cytotoxicity test: detection of menadione-catalyzed H2O2 production by viable cells.

Menadione-catalyzed H2O2 production by viable cells is proportional to viable cell number. The correlations between the viable cell number and the concentration of H2O2 produced are determined with the rapid chemiluminescent assay (S. Yamashoji, T. Ikeda, and K. Yamashoji, 1989, Anal. Biochem. 181, 149-152). This chemiluminescent assay of viable cells requires only 10 min and is much faster than NR (neutral red) inclusion and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) reduction assays, which require 3-5 h. When viable cells are incubated with antitumor drugs, detergents, mycotoxins, and glycoalkaloids for 24-48 h, a decrease in menadione-catalyzed H2O2 production in a dose- or incubation time-dependent manner is observed. In general, the 50% inhibition concentration determined by the chemiluminescent assay is lower than that determined by NR inclusion and MTT reduction assays, and the order of relative cytotoxic effects of agents is the same among these assays. Furthermore, clear cytotoxic effects are observed by the chemiluminescent assay after 1 h exposure of trypsinized cells to toxic compounds. Therefore, the chemiluminescent assay is expected to be more useful for the rapid detection of cytotoxic compounds than NR inclusion and MTT reduction assays.     

In-vitro cytotoxic and genotoxic effects of arsenic trioxide on human leukemia (HL-60) cells using the MTT and alkaline single cell gel electrophoresis (Comet) assays

Although arsenic trioxide (ATO) has been the subject of toxicological research, in vitro cytotoxicity and genotoxicity studies using relevant cell models and uniform methodology are not well elucidated. Hence, the aim of the present study was to evaluate the cytotoxicity and genotoxicity induced by ATO in a human leukemia (HL-60) cell line using the MTT [3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and alkaline single cell gel electrophoresis (Comet) assays, respectively. HL-60 cells were treated with different doses of ATO for 24 h prior to cytogenetic assessment. Data obtained from the MTT assay indicated that ATO significantly (P < 0.05) reduced the viability of HL-60 cells in a dose-dependent manner, showing a LD₅₀ value of 6.4 ± 0.6 μg/mL. Data generated from the comet assay also indicated a significant dose-dependent increase in DNA damage in HL-60 cells associated with ATO exposure. We observed a significant increase (P < 0.05) in comet tail-length, tail arm and tail moment, as well as in percentages of DNA cleavage at all doses tested, showing an evidence of ATO-induced genotoxic damage in HL-60 cells. This study confirms that the comet assay is a sensitive and effective method to detect DNA damage caused by heavy metals like arsenic. Taken together, our findings suggest that ATO exposure significantly (P < 0.05) reduces cellular viability and induces DNA damage in HL-60 cells as assessed by MTT and alkaline single cell gel electrophoresis assays, respectively.     

Tetrazolium [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] reduction by mycoplasmas.

We investigated 22 mycoplasma and acholeplasma species for their ability to reduce tetrazolium salts by using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. The test results were evaluated visually, as well as spectrophotometrically, by using an enzyme-linked immunosorbent assay reader. Our results were very similar to the results obtained when the tetrazolium salt reduction assay described by Aluotto et al. was used. However, the MTT reduction assay appeared to be better because it is faster, more objective and sensitive, easier to evaluate, and less expensive; in addition, it allows quantitative determinations. By using regression analysis a linear correlation between formazan production and the number of colony-forming units was demonstrated for all of the species investigated, indicating that the MTT assay can also be used for growth, toxicity, or chemosensitivity tests for the mycoplasma species that are capable of reducing tetrazolium salts.     

Localization of MTT formazan in lipid droplets. An alternative hypothesis about the nature of formazan granules and aggregates

MTT (3-(4, 5-dimethyl-2-thiazolyl)-2, 5-dihphenyltetrazolium bromide) assay is a widely used method to assess cell viability and proliferation. MTT is readily taken up by cells and enzymatically reduced to formazan, a dark compound which accumulates in cytoplasmic granules. Formazan is later eliminated by the cell by a mechanisms often indicated as exocytosis, that produces characteristic needle-like aggregates on the cell surface. The shape of formazan aggregates and the rate of exocytosis change in the presence of bioactive amyloid beta peptides (Abeta) and cholesterol. Though the cellular mechanisms involved in MTT reduction have been extensively investigated, the exact nature of formazan granules and the process of exocytosis are still obscure. Using Nile Red, which stains differentially neutral and polar lipids, and a fluorescent analog of cholesterol (NBD-cholesterol), we found that formazan localized in lipid droplets, consistent with the lipophilic nature of formazan. However, formazan granules and aggregates were also found to form after killing cells with paraformaldehyde fixation. Moreover, formazan aggregates were also obtained in cell-free media, using ascorbic acid to reduce MTT. The density and shape of formazan aggregates obtained in cell-free media was sensitive to cholesterol and Abeta. In cells, electron microscopy failed to detect the presence of secretory vesicles, but revealed unusual fibers of 50 nm of diameter extending throughout the cytoplasm. Taken together, these findings suggest that formazan efflux is driven by physico-chemical interactions at molecular level without involving higher cytological mechanisms.     

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) causes Akt phosphorylation and morphological changes in intracellular organellae in cultured rat astrocytes

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) is widely used for cell viability and cytotoxicity assays, but cell biological effects of MTT itself have not been investigated. In this paper we show that MTT induces a morphological change in an intracellular membranous compartment labeled with anti-Rab5 antibody, dissociation of early endosomal auto-antigen (EEA1) from the membrane fraction, and phosphorylation of Akt probably through a phosphatidylinositol-3-OH kinase [PI(3)K] pathway in cultured rat astrocytes. These findings suggest that MTT affects cellular functions and conditions to some extent, and such effects of MTT may cause some discrepancies of measurement of cell viability using MTT assay and other assays. That is, the effects of MTT on cells could influence the results of cell viability assay. Moreover, MTT or other tetrazolium salts could be used as interesting activators of Akt to investigate the mechanism by which Akt or PI(3)K is activated.     

一种新的以影像为基础的细胞增殖和细胞毒性检测方法

3-(4,5-二甲基-2-噻唑)-2,5-二苯基溴化四唑盐)（MTT）比色法是传统上检测细胞增殖和细胞毒性的常用方法.
CloneSelectTM成像系统是一种以影像为基础的用于分析细胞生长的可视检测系统.本研究采用人结直肠癌HCT116细胞系,运用CloneSelect成像系统和MTT方法分别检测药物阿的平的细胞毒性,并采用Bland Altman作图法比较两种实验方法获得的pEC50值,分析两种研究方法获得的结果的一致性. 结果表明,CloneSelectTM成像系统和MTT法获得的pEC50值具有较好的一致性.与MTT方法相比,基于影像的CloneSelectTM成像分析技术检测快速、无损伤且结果更准确,获取资料不损伤细胞,允许后续其它时间点或动力学检测. 研究提示,这种新的以影像为基础的检测技术可以替代MTT方法,用于分析不同药物的抗细胞增殖活性.     

Platinum complex cytotoxicity tested by the electrical resistance breakdown assay.

The electrical resistance breakdown assay provides a novel approach for the quantification of cytotoxic activity of platinum based anticancer drugs. It is a functional assay system for cancer cell invasion that detects nanoscale alterations of an epithelial test barrier prior to microscopic morphometric changes. We measured changes in transepithelial electrical resistance (TEER) of a tight epithelial MDCK-C7 monolayer in response to highly invasive amelanotic melanoma cells (A7-clone) in combination with different platinum complexes (cis-, oxali- and carboplatin). The efficiency of the electrical resistance breakdown assay was compared a standard method for measurement of cytostatic activity, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The MTT-assay utilizes mitochondrial enzymatic activity to draw conclusions from a functional cell metabolism to the number of living cells in a sample. When human melanoma cells were seeded on top of an electrically tight MDCK-C7 monolayer, electrical leakage occurred within 48 h of co-culture. Electrical resistance breakdown was effectively prevented by cisplatin and its analogs (no significant difference between 100 microM cisplatin and corresponding controls with non-invasive cells). The results of the electrical resistance breakdown and MTT-assay were linearly dependent. Significance of both tests was equivalent, but the electrical resistance breakdown assay gave additional functional information. Compared to oxali- and carboplatin, cisplatin was more effective in preventing TEER-breakdown than reducing the number of tumor cells, giving rise to the assumption that cisplatin can reduce tumor cell number as well as invasiveness. In conclusion the electrical resistance breakdown assay provides a sensitive, continuous and cell-based assay system for the quantification of cancer cell invasiveness and evaluation of chemotherapeutics under physiological conditions.     

Effects of high glucose concentration on survival and respiration of human endothelial cells.

To determine whether or not endothelial cell survival was decreased after incubation with high glucose concentrations in culture media, we studied the influence of D-glucose or L-glucose (a non-metabolizable stereoisomer of D-glucose) on cell survival using the trypan-blue exclusion test. Simultaneously, the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide) assay was used to measure both the mitochondrial respiratory chain activity and cell viability. Respiratory chain activity per cell increased when D-glucose concentrations rose but at the same time trypan-blue excluded cells were decreased. Comparison with data in the literature showed that the MTT assay was not reliable for studies involving endothelial cell survival when glucose reduction was affected on these cells. It seems important to check MTT assay reliability carefully when it is used for drugs affecting glucose metabolism, or with other cell types.     

Abeta mediated diminution of MTT reduction--an artefact of single cell culture?

The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) reduction assay is a frequently used and easily reproducible method to measure beta-amyloid (Abeta) toxicity in different types of single cell culture. To our knowledge, the influence of Abeta on MTT reduction has never been tested in more complex tissue. Initially, we reproduced the disturbed MTT reduction in neuron and astroglia primary cell cultures from rats as well as in the BV2 microglia cell line, utilizing four different Abeta species, namely freshly dissolved Abeta (25-35), fibrillar Abeta (1-40), oligomeric Abeta (1-42) and oligomeric Abeta (1-40). In contrast to the findings in single cell cultures, none of these Abeta species altered MTT reduction in rat organotypic hippocampal slice cultures (OHC). Moreover, application of Abeta to acutely isolated hippocampal slices from adult rats and in vivo intracerebroventricular injection of Abeta also did not influence the MTT reduction in the respective tissue. Failure of Abeta penetration into the tissue cannot explain the differences between single cells and the more complex brain tissue. Thus electrophysiological investigations disclosed an impairment of long-term potentiation (LTP) in the CA1 region of hippocampal slices from rat by application of oligomeric Abeta (1-40), but not by freshly dissolved Abeta (25-35) or fibrillar Abeta (1-40). In conclusion, the experiments revealed a glaring discrepancy between single cell cultures and complex brain tissue regarding the effect of different Abeta species on MTT reduction. Particularly, the differential effect of oligomeric versus other Abeta forms on LTP was not reflected in the MTT reduction assay. This may indicate that the Abeta oligomer effect on synaptic function reflected by LTP impairment precedes changes in formazane formation rate or that cells embedded in a more natural environment in the tissue are less susceptible to damage by Abeta, raising cautions against the consideration of single cell MTT reduction activity as a reliable assay in Alzheimer's drug discovery studies.     

Cell-based quantitative evaluation of the MTT assay

OBJECTIVE: To analyze the bioreduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) on a per cell basis and evaluate its modulation as a function of different stages of cell metabolism. STUDY DESIGN: Following MTT bioreduction, total optical density (TOD), cell area and specific activity (TOD/area) of V79 cells and cultured macrophages were recorded for individual cells by means of digital image analysis. The effect of different serum (0-10% vol/vol) or genistein (0-100 microM) concentrations was used to modulate the MTT-specific activity response. RESULTS: As cells in culture are heterogeneous in cell size, the contribution of each cell to the total amount of formazan formed per dish is variable. The production of formazan per cell as a result of MTT bioreduction was found to be proportional to cell size. CONCLUSION: Specific MTT-reducing activity was analyzed in phagocytes and nonphagocyte cells, revealing the utility of this variable in evaluating the MTT assay at the single-cell level.     

测定昆虫细胞存活或死亡的MTT方法的改进

MTT方法具有灵敏、简便、稳定可靠、不需同位素等特点。为了摸索测定昆虫细胞存活（或死亡）的MTT方法的各种最适条件,本文以中国棉铃虫细胞系为对象,确定了一些基本参数、并比较了三种MTT测定方法。结果表明：改进的方法所选用的溶剂——pH为4.5的3％SDS异丙醇效果最好,溶解甲所需时间短、OD值高。测定昆虫细胞范围为每孔500～60000细胞,测试波长为560nm,参考波长为690nm.     

MTT法用于药物对L2细胞毒性的实验研究

目的：评价噻唑蓝（MTT）法检测药物对细胞的毒性作用的可靠性。方法：大鼠肺泡上皮L2细胞以叔丁基对苯二酚（TBHQ）10．100μM,BsO以1-10mM分别处理,用MTT法检测细胞活性、JC-1（5,5’,6,6’-四氯．1,1’,3,3’-四乙基苯并咪唑羰花青碘化物）荧光染料法检测细胞线粒体电位改变、台盼蓝排斥实验检测细胞死亡率,分析各指标的情况。结果：在处理剂量范围,MTT法检测到的光密度（OD）值未能达到一般判断的半数抑制浓度（ic50）水平,最高抑制率仅达到30％左右;台盼蓝排斥试验检测数据表明TBHQ的LC50值为50μM,丁硫氨酸亚砜胺（BSO）为5mM;利用JC-1荧光染料判断的半数凋亡剂量分别为50μM和7mM。结论：MTT法作为最常采用的细胞生长抑制检测手段,但在某些特定实验中可能不能客观地反映细胞的活性,建议多种方法结合进行评价。