Abilities of wild-type and thymidine kinase-deficient Friend mouse erythroleukemia cells to undergo unscheduled DNA synthesis following mutagen treatment

The abilities of wild-type and thymidine kinase-deficient Friend mouse erythroleukemia cells to perform unscheduled DNA synthesis (UDS), through the incorporation of [³H]deoxycytidine, were measured following damage with methyl methane sulfonate (MMS), ethyl methane sulfonate (EMS), and ultraviolet (UV) irradiation. For each mutagenic treatment, a positive and quantitatively similar response was observed for both wild-type and thymidine kinase-deficient cells. The extent of the response varied greatly, however, depending upon the mutagen used. The results contrast with the unscheduled incorporation of [³H] thymidine in wild-type cells following mutagen treatment, where less variation between the positive UDS responses elicited by MMS, EMS, and UV treatments was observed. Nevertheless, the results clearly indicate that thymidine kinase deficiency does not prevent excision repair (UDS) from occurring.     

DNA-damaging potential of diethylstilbestrol evaluated in the germ cell unscheduled dna synthesis assay

Despite the fact that the nonsteroidal estrogen diethylstilbestrol (DES) exerts its toxic effects primarily on the reproductive system, little is known about the possible interference of this compound with germ cell DNA. The measurement of unscheduled DNA synthesis (UDS) in spermatocytes and early spermatids of mice germ-cells is a valid indicator for the DNA-damaging potential of a compound. UDS occurrence was thus determined after IP administration of 10, 30, 60 or 180 mg/kg DES to male mice. Tritiated thymidine ([³H]dThd) was then injected into the testes, the spermatozoa were serially collected, the sperm heads isolated, and UDS determined by the amount of [³H]dThd incorporation. [³H]dThd measurements in germ cells of mice which were treated with 10 mg/kg DES were comparable to those of the controls. Higher incorporation of [³H]dThd, indicating UDS, was measured in sperm cells which had been spermatocytes at the time of treatment with 30 and 60 mg/kg DES; this increase was statistically significant at 60 mg/kg. Administration of 180 mg/kg DES caused [³H]dThd incorporation which was comparable to that of the controls, suggesting that DES interfered with repair mechanisms or delayed spermatogenic cycles at high dose levels. General toxicity was manifested in a dose-dependent decrease of the sperm cell numbers in the spermatogenic stages investigated. This study provides evidence that DES, or its metabolite(s), reached the germ cells of adult mice in sufficient amounts to produce DNA damage. The levels of radioactivity measured were comparable to those measured after cyclophosphamide treatment, but [³H]dThd incorporation was about 10 times less than in methylmethane sulfonate-treated animals.     

Characterization of vaccinia virus DNA replication in vitro

Concentrated cytoplasmic preparations from vaccinia virus strain WR-infected HeLa S3 cells were shown to replicate viral DNA in vitro. Incorporation of [³H]dTTP was linear for about 40 min and reached a plateau suggesting that no new rounds of viral chromosome replication were initiated. The synthesis of viral DNA was sensitive to ultraviolet irradiation and 10 μM N-ethylmaleimide. The ability of the in vitro system to support maximal DNA replication was dependent on the four deoxyribonucleoside triphosphates, ATP, and an ATP-generating system, and was stimulated by ribonucleoside triphosphates. DNA was synthesized in vitro as short chains which elongated to form high-molecular-weight DNA. At least 60% of the DNA was synthesized semiconservatively as evidenced by density shifting in CsCl after BrdUTP incorporation. DNA hybridization experiments showed that in vitro synthesized DNA consisted of virus-specified sequences. Cytoplasmic, or loosely bound factors were necessary for continued replication, since washed inclusions incorporated lower amounts of [³H]dTTP. Activity could be restored by addition of soluble proteins from the cytoplasm of infected cells.     

Induction of cellular DNA synthesis by a temperature-sensitive mutant of herpes simplex virus type 2.

A temperature-sensitive mutant (ts 4) of herpes simplex virus type 2 (HSV-2), having the ability to transform hamster embryo (HaE) cells at the nonpermissive temperature of 38.5°, has been investigated in several aspects. It is defective in thymidine (TdR) kinase induction at both the permissive (34°) and the nonpermissive temperatures and defective in viral DNA synthesis at the nonpermissive temperature. However, stimulation of chromosomal DNA synthesis was detected at 16–28 hr after infection at the nonpermissive temperature in HaE cells arrested with low serum concentration. DNA synthesis was estimated by the incorporation of [³H]TdR or [³H]CdR (deoxycytidine) into DNA, and differentiation of cellular from viral DNA was performed by buoyant density gradient centrifugation in CsCl or by DNA-DNA hybridization. By autoradiography with [³H]TdR, it was found that the number of cells with grains in the nuclei increased in infected cultures at 16–28 hr after infection. Virus exposed to heat or uv light lost the ability to induce cellular DNA synthesis, indicating that active virus is responsible for stimulation of cellular DNA synthesis.     

Dual pathway of B lymphocyte differentiation in vitro

Direct visualization of the events resulting from LPS stimulation of mouse spleen cells in vitro was achieved by characterizing the cells during four days of culture for morphology, Ig and Θ surface markers and autoradiography after [³H] thymidine uptake. The changes observed were related to biochemical parameters such as incorporation of [³H] thymidine into DNA, Ig biosynthesis and secretion. Two pathways of B lymphocyte differentiation were observed: a) the generation of a large number of small B lymphocytes with high density of surface Ig but no internal pool detectable by immunofluorescence, and b) the maturation of a very small proportion of cells with a large intracellular pool and the ability to secrete Ig. Both cell types arise from dividing blast cells, either physically separated or traced by pulse chase experiments with [³H] thymidine. We discuss whether this duality is caused by the triggering of different B cell subpopulations at different developmental stages, preprogramed to one or the other pathway or whether the final direction of development depends on the microenvironment of individual dividing cells.     

血小板源生长因子对人血管成纤维细胞DNA及胶原蛋白合成的影响

目的:观察血小板源生长因子对培养的人血管成纤维细胞DNA及胶原蛋白合成的影响。方法:采用培养的人血管成纤维细胞,应用 [³H]-TdR和 [³H]-脯氨酸掺入的方法,观察血小板源生长因子-BB对人血管成纤维细胞DNA合成以及胶原蛋白合成的影响。结果:血小板源生长因子-BB可促进静止状态的人血管成纤维细胞DNA及胶原蛋白的合成,在 30μg/L浓度时DNA及胶原蛋白的合成达到高峰,DNA及胶原蛋白分别于 2 4h和 36h合成最为显著。结论:血小板源生长因子-BB可明显促进培养的人血管成纤维细胞DNA及胶原蛋白的合成     

Role of deoxynucleoside triphosphate pools in the cytotoxic and mutagenic effects of DNA alkylating agents

The objective of these studies was to define the role of deoxynucleoside triphosphate pools in the cytotoxic and mutagenic effects of DNA alkylating agents. Survival of Chinese hamster ovary (CHO) cells after treatment with DNA alkylating agents was clearly related to the balance of the dCTP and dTTP pools—high dCTP/dTTP ratios increased the survival of CHO cells 2- to 10-fold compared to treatment in low dCTP/dTTP. Induction of mutations at three genetic loci by one agent, ethyl methane sulfonate (EtMes) was also affected by pool alterations. Although the maximum mutagenesis obtained in high or low dCTP/dTTP was not significantly different, it took considerably lower concentrations of EtMes to obtain this maximum in conditions giving low dCTP/dTTP. These results are consistent with a common mechanism: mispairing of thymine with the O⁶-alkylatedguanine—causing both the cytotoxic and mutagenic effects of EtMes. They also suggest that alterations of dCTP/dTTP ratio may be involved in certain human genetic diseases characterized by increased sensitivity to DNA alkylating agents.     

Stimulation of DNA synthesis in mouse lymphoid cells by polyanions in vitro. I. Target cells and possible mode of action

The effect of dextran sulfate on [³H]dThd incorporation in lymphoid cells was investigated. The polyanion activated DNA synthesis in spleen and bone marrow cells of normal mice. The highest rate of activation was detected in spleen cells of athymic (nude) mice; the ratio of [³H]dThd incorporation was higher in TxBM spleen cells of thymectomized, lethally irradiated and bone marrow protected mice than in spleen cells of normal donors. Thymus cells of normal mice could not be stimulated, but a slight response was obtained in cortisone-resistant thymus cells. A synergetic effect was found in normal thymus cells using a combination of dextran sulfate and phytohemagglutinin (PHA). In contrast, lipopolysaccharide and PHA showed no synergetic effect. The possible mode of action of polyanions as de-repressors of DNA synthesis is discussed.     

牛磺酸减轻β-甘油磷酸诱导的大鼠血管平滑肌细胞钙化氧化应激在反流物所致食管粘膜损伤中的作用

目的：观察牛磺酸对钙化的形成及逆转作用的影响，探讨牛磺酸在血管钙化发生中的作用。方法：利用β-甘油磷酸制备钙化血管平滑肌细胞（VSMCs），测定细胞钙含量、碱性磷酸酶活性、[⁴⁵Ca]沉积及[³H]-胸腺嘧啶。结果：与对照组相比，钙化细胞的钙含量、ALP活性和[⁴⁵Ca]沉积均明显升高（P<0.05），而牛磺酸与β-甘油磷酸同时孵育呈剂量依赖性地抑制钙化发生。在牛磺酸逆转实验中，钙化细胞的钙含量、ALP活性和[⁴⁵Ca]沉积均较换液前明显降低（P<0.01）；且牛磺酸呈剂量依赖性地逆转已钙化细胞。与对照组相比，钙化细胞的细胞数量和[³H]-TdR掺入量增加（P<0.01），牛磺酸早期干预组显著抑制钙化细胞的增殖，但牛磺酸对已钙化的细胞,增殖抑制效应不明显。结论：牛磺酸可抑制细胞钙化形成且能逆转已形成钙化。     

Replication of vaccinia DNA in mouse L cells. II. In vitro DNA synthesis in cytoplasmic extracts.

Cytoplasmic extracts prepared from vaccinia virus-infected L cells catalyzed the incorporation of labeled deoxynucleotide triphosphates into DNA which hybridized with vaccinia virus DNA. The incorporation of [³H]thymidine 5′ triphosphate ([³H]TTP) into DNA was shown to be dependent on the presence of all four deoxynucleoside triphosphates and incorporation was stimulated twofold by the addition of ATP, NAD, and ribonucleoside triphosphates. The incorporation of [³H]TTP in vitro was linear for 10 min and continued at a reduced rate for 30 min at 30°. The viral DNA synthesized in vitro was analyzed by sedimentation in alkaline-sucrose gradients and by isopycnic centrifugation in CsCl gradients. Alkaline-sucrose sedimentation analysis showed that replication of in vitro labeled DNA was discontinuous. Small fragments (～10 S) were synthesized in vitro in 10–30 sec which appeared to elongate so that after 30 min of synthesis the in vitro synthesized molecules cosedimented with in vivo labeled viral DNA species of 10–70 S. No molecules of greater length than mature viral single-stranded DNA (Type 1, 70–72 S) were observed when cell extracts prepared 3 hr postinfection were employed. Replication of viral DNA in vitro was symmetrical. No evidence for circular or superhelical DNA duplex molecules was obtained when in vitro synthesized DNA was analyzed by equilibrium density centrifugation in CsCl containing ethidium bromide.     

Radiosensitivity of T and B lymphocytes. II. Effect of irradiation on response of T cells to alloantigens

The radiosensitivity of T cells was investigated by studying the effect of irradiation in vitro in suppressing the capacity of parental strain thoracic duct lymphocytes (a) to induce splenomegaly in newborn F₁ mice, and (b) to proliferate in adult irradiated F₁ mice as measured by incorporation of tritiated thymidine ([³H]dThd) 4 days after transfer. By these parameters, small T lymphocytes were found to be highly radiosensitive. It was calculated that, of cells with the reactivity to the alloantigens studied, 0.3 % were capable of a proliferative response after exposure to 500 r. Radiosensitivity was considered to be a reflection of lymphocyte death in interphase. The radiosensitivity of H-2-activated T cells (T. TDL) differed from that of small T cells. Thus, [³H]dThd incorporation by T. TDL measured 1 day after transfer to irradiated F₁ hosts was not abolished, although lowered, by exposure to doses as high as 5000 r; [³H]dThd incorporation measured at 2 days, however, was greatly reduced by much smaller doses of irradiation. In view of evidence obtained elsewhere that the response of T. TDL to alloantigens involves DNA synthesis but not cell division, the present studies were interpreted in terms of irradiation causing death of T. TDL in interphase before entry into DNA synthesis. It was concluded that T. TDL were far more resistant to irradiation-induced interphase death than were small T cells. The small numbers of lymphocytes obtained from thoracic duct lymph of mice exposed to whole body irradiation 4 days before consisted almost entirely of T cells; these cells, although viable, were found incapable of mounting a proliferate response when exposed to alloantigens on transfer.     

DNA synthesis in isolated hepatocytes infected with herpesviruses

The ability of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) and human cytomegalovirus (HCMV) to replicate, synthesize virus DNA, and stimulate incorporation of [³H]thymidine into cell DNA in isolated adult rat hepatocytes has been studied. HSV-1 replicated in these cells by 22–30 hr postinfection (p.i.) to yields that exceeded the input amount of virus. In contrast, HSV-2 replicated poorly. Replication of HSV-2 was unaltered whether hepatocyte monolayers were prepared by plating directly on plastic dishes or plating on a collagen gel/nylon mesh substratum. After HCMV infection, no cytopathology was evident and virus was not detectable by plaque titration. HCMV infection stimulated incorporation of [³H]thymidine into hepatocyte DNA but HCMV DNA was not detectable. Significant levels of HSV-1 DNA were synthesized by 23 hr p.i. with HSV-1 but incorporation of the radiolabel into the cell DNA peak was reduced. In contrast, HSV-2 showed not only a significant level of virus DNA, but incorporation of [³H]thymidine into the cell DNA peak, was markedly increased by 23 hr p.i. over that in mock-infected cultures. HSV-2-induced stimulation of radiolabel incorporation into hepatocyte DNA was: (i) eliminated when HSV-2 was heat inactivated for 2 hr at 56°, (ii) dependent on virus multiplicity, and (iii) maximal at 22–25 hr p.i. with 10 PFU of HSV-2 per cell. Autoradiography of HSV-2-infected cultures revealed that at 10–13 hr p.i. 3870 of the cells in the hepatocyte monolayer were labeled. We conclude that nonproliferating differentiated hepatocytes: (i) can support the synthesis of HSV-1 and HSV-2 DNAs, (ii) can support the replication of HSV-1 and HSV-2, and (iii) show increased incorporation of [³H]thymidine into hepatocyte DNA after infection with either HCMV or HSV-2. It is of particular interest that in HSV-2 infection of hepatocytes in which virus DNA is made, incorporation of label into host DNA is not suppressed but is stimulated.     

Partial pronase digestion of rat gastric mucosa isolates cells undergoing replicative DNA synthesis

A pronase digestion procedure for the isolation of gastric mucosal cells was evaluated for its usefulness in measuring unscheduled DNA synthesis (UDS). The method has been claimed to be suited for assessing the genotoxicity potential of compounds. Compounds were given orally to rats. After 13 h [3H]thymidine was injected and after another hour the animals were killed. The dissected stomachs were treated with pronase for 45 min and the incorporation of radioactivity into DNA was determined. Autoradiography was also performed both on the mucosa and on the isolated cell suspension. The cell suspensions were found to include cells undergoing normal replicative (S phase) DNA synthesis. Of all cells isolated, 4.8 +/- 0.6% consisted of S phase cells. The total amount of DNA recovered (corresponding to the number of cells isolated) was variable and ranged from 20 to 671 micrograms DNA, i.e. approximately 30-fold variation. Neither omeprazole (10, 30 and 80 mg/kg) nor ranitidine (215 mg/kg) had any effect on [3H]thymidine incorporation. The known carcinogen 1-methyl-3-nitro-1-nitrosoguanidine (MNNG) increased incorporation. Refeeding of fasted animals increased incorporation of [3H]thymidine almost 4-fold, showing that animal feeding status influences incorporation. Hydroxyurea, the selective inhibitor of S phase DNA synthesis, inhibited [3H]thymidine incorporation in control and omeprazole-treated animals as well as that induced by MNNG by 92-98%. The results clearly show that the pronase digestion procedure used releases cells undergoing normal, replicative DNA synthesis and can therefore neither be used for measurements of UDS nor for the assessment of the genotoxic potential of drugs.     

RNA-nascent DNA complexes in Ehrlich ascites tumor cells in vivo

When mice bearing Ehrlich ascites tumors were given a single intraperitoneal injection of [5-³H]uridine, the ascites cells incroporated radioactivity into DNA for 4 hr, while incorporation into total cellular RNA ceased after 20–30 min. Nascent DNA, isolated by Cs₂SO₄ isopycnic centrifugation 30 min, 4 hr or 50 hr after [5-³H]uridine injection contained RNA fragments. Treatments with hydroxyurea, an inhibiton hibitor of DNA synthesis, reduced the incorporation of [5-³H]uridine into the DNA-RNA complex to 43% of controls. Treatment with actinomycin D, an inhibitor of DNA-dependent RNA synthesis, abolished the incorporation of [5-³H]uridine into the DNA-RNA complex. Finally, when DNA was pulse-labeled with [¹⁴C]deoxythymidine and then denatured by heat-treatment, it banded in a region with a higher density than that of reference DNA. However, if treated with alkali, it banded at the density of reference DNA, again suggesting the presence of RNA fragments in nascent DNA. The length of the RNA chains in this DNA-RNA complex was estimated to be in the order of 70 nucleotides.     

Cytopathogenicity ofEntamoeba histolytica: Trophozoite homogenates modulate DNA synthesis in a mammalian cell line

We examined the effect of total trophozoite homogenates from four axenized strains ofEntamoeba histolytica (HK9, HM1, HM2, and HM3) on the DNA synthesis of subconfluent cultures of Chinese hamster ovary (CHO) cells incubated at low (0.1%) serum concentration. HM1, HM2, and HM3 extracts increased [³H]thymidine incorporation to acidinsoluble material in CHO cells up to a maximum of 2.5, 1.5, and 1.5 times respectively, at doses of amebal protein ranging from 16 to 125 g/ml. HM1 and HM2 extracts at doses higher than those causing maximal stimulation, and HM3 and HK9 extracts above 250 g protein per ml, progressively inhibited [³H]thymidine incorporation by CHO cells at a strain-specific rate. The extracts with both the most potent stimulatory and inhibitory effects were those from HM1 and HM2, also the most virulent strains. This strain-specific ability of amebal products to modulate cell DNA synthesis may play a significant role in amebal virulence.     

Human fetal colon in organ culture

Summary Human fetal colon (14–16 weeks gestation) was cultured as explants for 15 days in serum-free Leibovitz L-15 medium at 37°C. The overall morphology of the colonic explants was well maintained throughout the culture period and all epithelial cell types retained their ultrastructural characteristics. The incorporation of [³H]-leucine continued and even increased, reflecting sustained synthesis of proteins. Even though the incorporation of [³H]-thymidine into the total DNA decreased during culture, the synthesis of DNA continued. The sites of [³H]-thymidine incorporation into the different layers of the colonic wall were studied by radioautography. The incorporation of the radioactive precursor occurs mainly in the epithelium and to lesser degrees in the mesenchyme and the muscular layer. Labeled epithelial nuclei were located in the intervillous areas but not on the villi. The labeling index of the epithelial cells remained constant throughout the culture period indicating the preservation of the proliferative capacity of the epithelium. Brush-border hydrolytic activites, namely those of sucrase, maltase, lactase, trehalase, glucoamylase and alkaline phosphatase, were assayed in the colonic tissue. These enzymic activities generally decreased in the tissue and increased in the medium during the course of culture. These observations clearly demonstrate that fetal colon can be maintained viable for at least 15 days in a serum-free medium. Organ culture now provides the opportunity to study the normal function and metabolism of human colon during its development.     

Induction of DNA damage by urethane in mouse testes: DNA binding and unscheduled DNA synthesis

The extent and persistence of DMA damage and repair were investigated in mouse spermatogenic cells exposed in vivo to urethane (ethyl carbamate, EC). Adult male mice exposed to [³H]EC at 10–1,000 mg/kg were sacrificed 12 hr later. EC/metabolite binding to liver and testicular DNA and to sperm heads from the vasa deferentia was measured. Other male mice were exposed to EC at 50–750 mg/kg, and unscheduled DNA synthesis (UDS) induction was investigated in early spermatid stages. Similar experiments were conducted with vinyl carbamate (VC; putative EC metabolite) at 10–75 mg/kg. [³H]EC bound to liver and testicular DNA and to whole sperm heads. Testicular DNA binding increased linearly with dose, although binding was at least 2 orders of magnitude lower than with liver DNA. Sperm head binding also increased linearly with dose. Dose response studies with the UDS assay showed that EC and VC induced a small but significant increase of the UDS response in early spermatid stages. However, the induced UDS responses were quite variable and did not consistently increase with the administered dose. To determine the time kinetics of UDS induction, [³H]dThd was injected at various times after treatment with 500 mg/kg of EC or 60 mg/kg of VC. A slight but significant UDS increase was observed 4 hr after treatment with EC but not with VC. Overall, these results suggest that EC metabolites bind to testis DNA and cause low-level DNA damage in mouse sper-matogenic cells. This type of DNA damage apparently does not have significant genetic consequences. © 1994 Wiley-Liss, Inc.     

奥曲肽抑制肝星状细胞增殖及细胞外基质合成

目的:探讨奥曲肽对肝星状细胞(HSC)增殖与细胞外基质(ECM)合成的影响。方法:采用胶原酶二步原位灌注法分离、培养大鼠HSC,并分别给予转化生长因子1(TGFβ1)(2.5μg·L^-1)、奥曲肽(Oct)(0.01-10μg·L^-1)或TGFβ1(2.5μg·L^-1)+Oct(0.01-10mg·L^-1)干预,分别用MTT法、[³H]-TdR和[³H]-脯氨酸掺入法及放射免疫法检测各处理组HSC增殖及ECM合成水平。结果:Oct能不同程度抑制HSC[³H]-TdR掺入和增殖;能够显著抑制体外培养HSC[³H]-脯氨酸掺入,降低上清液透明质酸(HA)、层粘连蛋白(LN)和IV型胶原(CIV)水平;TGFβ1能够诱导HSC表达ECM上调,Oct能够阻断TGFβ1对HSC的调控作用。结论:Oct能够有效地抑制HSC增殖及ECM合成与分泌。     

Incorporation of [3H]thymidine into the spleen of intact mice during the immune response to sheep erythrocytes (SRC)

The incorporation of [³H]thymidine, administered shortly before killing, into the spleens of intact mice during the primary immune response to SRC has been studied, using autoradiography with exposure periods of 184 days before development.

A mixture of weakly and heavily labelled nuclei were situated in well-defined areas of the follicles. A marked increase of heavily labelled nuclei coincided with an increased uptake of [³H]thymidine into the spleen DNA during the first 3 days of the immune response. At this time the number of lightly labelled nuclei in the follicles was reduced. The heavily labelled nuclei were first apparent in the periarteriolar zone, then in germinal centres spreading out into the red pulp. After the peak of [³H]thymidine incorporation was over (day 3–4) weakly-labelled nuclei accumulated in the red pulp and persisted until day 9 after the injection of SRC.

It was concluded that many non-dividing cells in mouse spleen were incorporating small amounts of [³H]thymidine into their nuclear DNA. In view of the accumulation of such cells in the red pulp during the course of the immune response to SRC, it was considered that this evidence of DNA synthesis was a manifestation of metabolic turnover of this molecule and relevant to the immune process. From the data presented it was also concluded that only a small proportion of the total spleen population engaged in DNA synthesis and proliferation were actually induced to produce specific antibodies. This preliminary investigation showed the complex nature of the immune process leading to antibody synthesis, which requires much further detailed study.

     

红景天甙对低氧培养的兔肺动脉平滑肌细胞增殖的抑制作用

目的:研究红景天甙(Salidroside,Sal)对低氧(3%)条件下兔肺动脉平滑肌细胞(PASMC)增殖、DNA合成、细胞内钙离子浓度的影响。方法:应用细胞培养、四唑盐比色试验(MTT)、[³H]-胸腺嘧啶核苷([³H]-TdR)掺入试验、Fluo-3和激光扫描共聚焦显微术测定细胞内Ca²⁺浓度等方法。结果:低氧24h可直接刺激PASMC,使MTT的A值增加62%(P＜0.05),[³H][³H]-TdR掺入量增加138%(P＜0.01)。在低氧的PASMC培养液中加入Sal(32×10^-5mol/L)可抑制低氧的这种促增殖作用,与低氧组相比MTT的A值下降29%(P＜0.05),[³H][³H]-TdR掺入量下降37%。在低氧的PASMC培养液中加入钙通道阻滞剂verapamil也可抑制低氧的促增殖作用,与低氧组相比较,MTT的A值下降23%(P＜0.05),[³H][³H]-TdR掺入量下降51%(P＜0.01)。PASMC的低氧培养可使细胞内Ca²⁺浓度明显增加(P＜0.05),Sal可抑制低氧所致的细胞内Ca²⁺浓度的上升。结论:红景天甙可抑制低氧促进PASMC增殖、DNA合成的作用,其机制可能与抑制低氧时细胞内Ca²⁺浓度增加有关。