Comparative effects of ASTA Z 7557 (INN mafosfamide) and cyclophosphamide on hematopoiesis in mice

Summary Acute effects of ASTA Z 7557 and Cyclophosphamide (Cy) on pluripotential (CFU-S), granulocytic (CFU-C), early erythroid (BFU-E) and late erythroid (CFU-E) progenitor cells in the bone marrow, as well as on RBC and WBC, were compared in F₁ (CBA × C 57 BL) female mice. Dose-survival curves of both agents for CFU-S and CFU-C were found to be exponential, indicating that the effects of the drugs have no cell cycle dependency. At equimolar doses, marrow CFU-S and CFU-C contents appeared to decrease more rapidly with increasing doses of ASTA Z 7557 than with those of Cy. After a single dose of 200 mg/kg of each drug (= 50% LD₁₀), there was greater initial suppression of CFU-S, CFU-C, BFU-E and CFU-E in the Cy-treated animals than in ASTA Z 7557-treated mice. In both groups, however, the WBC had their nadir on Day 3 after treatment, followed by a return to normal by Day 8. In ASTA Z 7557-treated animals, the recovery of CFU-S, CFU-C and BFU-E was also completed by Day 8 after treatment. In Cy-treated mice, however, complete recovery of these cells was achieved on Day 15. Results indicate quantitative rather than qualitative differences between the marrow toxicities of ASTA Z 7557 and Cy in mice. Quantitative differences could be due to different pharmacokinetic properties of the agents, since Cy is excreted in partially unmetabolized form, and it might be that this inactive part of the agent grew with increasing drug doses.     

A comparative study of therapeutic activity,myelotoxicity and DNA damage in the bone marrow of mice after cyclophosphamide and ASTA Z 7557 (INN mafosfamide)

Summary This study compares the two oxazaphosphorine compounds ASTA Z 7557 (AZ) and cyclophosphamide (CP) in their therapeutic activity as well as in their myelotoxicity and DNA damage being induced after a single intraperitoneal injection. Therapeutic activity was determined towards methylnitrosourea-induced rat mammary carcinomas in vivo and in vitro, resulting in comparable efficacy of both compounds at their optimal doses, respectively, with the sensitivity of individual tumors being reflected by the degree of inhibition of ³H-thymidine uptake of these cells in vitro.Myelotoxicity was measured as inhibition of pluripotent (CFU-S) and macrophage-granulocyte committed (CFU-C) stem cells together with the extent of single strand breaks and DNA-DNA interstrand crosslinks in murine bone marrow. At equimolar base AZ was found to induce a higher level of DNA damage than CP in the bone marrow of mice 16 hours after a single intraperitoneal injection. Both compounds depressed the pluripotent stem cell compartment of the bone marrow to a similar extent, whereas AZ was significantly less toxic to the granulocyte cell lineage.Abbreviations AZ ASTA Z 7557; 2-[N,N,bis-(2-chloroethyl)-amino]-4-(2-sulphonato-ethylthio)-tetrahydro-2H-1,3,2, oxazaphosphorine-2-oxide - CP Cyclophosphamide; 2-[N,N,bis-(2-chloroethyl)-amino]-1,3,2-oxazaphosporine-2-oxide - CFU-C Granulocyte-committed stem cells - CFU-S Pluripotent stem cells - BCNU 1,3-bis(2-chloroethyl)-1-nitrosourea - MNU N-methyl-N-nitrosourea - Mesna 2-mercaptoethanesulphonate     

Effects of diallyl trisulfide on induction of apoptotic death in murine leukemia WEHI‐3 cells in vitro and alterations of the immune responses in normal and leukemic mice in vivo

Diallyl trisulfide (DATS), a chemopreventive dietary constituent and extracted from garlic, has been shown to against cultured many types of human cancer cell liens but the fate of apoptosis in murine leukemia cells in vitro and immune responses in leukemic mice remain elusive. Herein, we clarified the actions of DATS on growth inhibition of murine leukemia WEHI‐3 cells in vitro and used WEHI‐3 cells to generate leukemic mice in vivo, following to investigate the effects of DATS in animal model. In in vitro study, DATS induced apoptosis of WEHI‐3 cells through the G0/G1 phase arrest and induction of caspase‐3 activation. In in vivo study DATS decreased the weight of spleen of leukemia mice but did not affect the spleen weight of normal mice. DATS promoted the immune responses such as promotions of the macrophage phagocytosis and NK cell activities in WEHI‐3 leukemic and normal mice. However, DATS only promotes NK cell activities in normal mice. DATS increases the surface markers of CD11b and Mac‐3 in leukemia mice but only promoted CD3 in normal mice. In conclusion, the present study indicates that DATS induces cell death through induction of apoptosis in mice leukemia WHEI‐3 cells. DATS also promotes immune responses in leukemia and normal mice in vivo. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 1343–1353, 2015.     

A novel compound N,N-(Z)-N-(E)-tri-p-coumaroylspermidine isolated from Carthamus tinctorius L. and acting by serotonin transporter inhibition

Safflower, the dry flower of Carthamus tinctorius L., has long been applied for empirically treating cerebral ischemia and depression in traditional Chinese medicine. Pathogenesis of major depression involves monoaminergic transmission. The present study assessed whether safflower or its isolate would be effective in functionally regulating monoamine transporter using in vitro screening cell lines. We discovered that safflower insoluble fraction significantly inhibited serotonin uptake in Chinese hamster ovary cells stably expressing serotonin transporter (i.e. S6 cells). This fraction went through an activity-guided isolation and an active ingredient was obtained, which was subsequently elucidated as a novel coumaroylspermidine analog N¹,N⁵-(Z)-N¹⁰-(E)-tri-p-coumaroylspermidine using NMR techniques. Pharmacologically, this compound potently and selectively inhibited serotonin uptake in S6 cells or in synaptosomes, with IC₅₀ of 0.74 ± 0.15 µM for S6 cells or 1.07 ± 0.23 µM for synaptosomes and with a reversible competitive property for the 5HT-uptake inhibition. The potency of it for 5HT uptake was weaker than that of fluoxetine whereas efficacy generally similar for both. Animals treated with this testing compound showed a significant decrease in synaptosomal 5HT uptake capacity. Thus, N¹,N⁵-(Z)-N¹⁰-(E)-tri-p-coumaroylspermidine is a novel serotonin transporter inhibitor, which could improve neuropsychological disorders through regulating serotoninergic transmission.     

Analysis of heterogeneity in daunorubicin uptake by human leukemia cells using laser flow cytometry

Summary Heterogeneity in daunorubicin uptake by leukemic blast cells obtained from the bone marrow of 16 patients with acute leukemia (10 acute nonlymphocytic leukemia and 6 acute lymphocytic leukemia) was determined by laser flow cytometry following drug treatment in vitro for 1 hr. Fluorescence profiles of cellular anthracycline levels in the various samples indicated a marked heterogeneity in daunorubicin uptake and the range of detectable drug fluorescent cells was 34% – 99%. A retrospective analysis of disease outcome in these patients who were treated with a daunorubicin or doxorubicin containing induction regimen indicated the following: (a) 8 of 11 patients who entered complete remission had > 80% of leukemic blast cells accumulating detectable amounts of daunorubicin; and (b) 3 of 4 patients who did not respond to chemotherapy had < 40% of the leukemic blast cells accumulating detectable amounts of daunorubicin. These results suggest that laser flow cytometry may be useful in determining qualitative and quantitative differences in daunorubicin levels in heterogeneous tumor cell populations.     

5-Hydroxytryptamine 5-HT1D receptors mediating inhibition of cyclic AMP accumulation in Madin-Darby canine kidney (MDCK) cells

5-Hydroxytryptamine 5-HT_1B/5-HT_1D receptors are members of the same receptor subfamily, but display a different pharmacology (Hartig et al. (1992) Trends Pharmacol Set 13:152–159). Whereas several cell lines have been reported to contain 5-HT_1B receptors, none has been described, however, that endogenously expresses well-characterized 5-HT_1D receptors. The present study deals with the identification of 5-HT_1D receptors inhibiting cyclic AMP accumulation in Madin-Darby canine kidney (MDCK) cells. 5-HT (1 nM– 10 M) induced a concentration-dependent inhibition of the cyclic AMP accumulation stimulated by prostaglandin E₁ (1 M) in MDCK cells. The maximal effect of 5-HT averaged 50% inhibition and was abolished after a pre-treatment of the cells with pertussis toxin. Other agonists mimicked the effects of 5-HT, with the following rank order of potency (pEC₅₀ ± SEM, n 3): 5-carboxamidotryptamine (8.36 ± 0.48) > PAPP (p-aminophenylethyl-m-trifluoromethylphenyl piperazine, 7.89 ± 0.23) > 5-HT (7.35 ± 0.05) > sumatriptan (6.65 ± 0.27). PAPP behaved as a partial agonist. 8-OH-DPAT (8-hydroxy-2(di-n-propylamino)tetralin) was less potent, its maximal effect being not reached at 0.1 mM. Methiothepin, GR127935, (–)propranolol, rauwolscine and ketanserin were all devoid of intrinsic activity (up to 10 M or 0.1 mM). Methiothepin (10 nM, 0.1 M and 1 M) antagonized 5-HT effect (pA₂ 8.57 ± 0.44, Schild slope 1.17 ± 0.21, n = 3). GR127935 (1 nM, 10 nM and 0.1 M) shifted the curve of 5-HT to the right, but the antagonism was not fully surmountable (apparent pK_B value, 9.80 ± 0.16, n = 9). From the shifts obtained with rauwolscine (1 M) and (–)propranolol (10 M), respective pK_B values were estimated 6.68 ± 0.30 and 5.4 (n = 3 each). PAPP, when tested as an antagonist at 1 M, also shifted the curve of 5-HT to the right, with a pK_B of 8.27 ± 0.16 (n = 3). Finally, ketanserin (10 M) also antagonized the effects of 5-HT, the pK_B being 6.54 ± 0.16 (n = 9). The rank orders of agonist and antagonist potencies strongly suggest 5-HT receptors mediating inhibition of cyclic AMP accumulation in MDCK cells to be 5-HT_1D receptors. This is the first report of a cell line expressing endogenous, well-characterized, 5-HT_1D receptors. With regard to the 5-HT_1D receptor subtype involved, the relatively high potency of ketanserin would suggest it to be a 5-HT_1D subtype or a mixture of 5-HT_1D/5-HT_1D\ subtypes. However, caution must be exercised here, owing to the poor knowledge of canine 5-HT_1D receptor subtypes.     

In Vitro Permeability Across Caco-2 Cells (Colonic) Can Predict In Vivo (Small Intestinal) Absorption in Man—Fact or Myth

Purpose. To evaluate and optimize the use of Caco-2 cell monolayers to predict thein vivo absorption of a broad range of compounds in man. Methods. Caco-2 cells are derived from human adenocarcinoma colon cells and spontaneously differentiate when grown on porous polyethylene terephthalate membranes (PETP) in a 12 well format to form monolayers of polarized cells possessing function similar to intestinal enterocytes. Transport experiments were conducted using 21 day cultured cells in a shaking water bath at 37°C. Radiolabeled mannitol was used to determine monolayer integrity. Apparent permeability coefficient (P_app) was calculated from the appearance of drug in the receiver side. Results. A strong correlation was observed between in vivo human absorption and in vitro P_app for a variety of compounds (R = 0.95, N = 35). For compounds that are substrates of p-glycoprotein (Pgp), use of a Pgp inhibitor resulted in a better estimate of absorption in humans. The results of this study suggest that the overall ranking of compounds with P_app < 1 × 10^–6 cm/sec, between 1–10 × 10^–6 cm/ sec, and > 10 × 10^–6 cm/sec can be classified as poorly (0–20%), moderately (20–70%) and well (70–100%) absorbed compounds, respectively. Conclusions. These data suggest that Caco-2 cells developed under the culturing and transport conditions defined herein can be used to predict in vivo human absorption of compounds regardless of transport mechanism, viz., transcellular, paracellular and carrier-mediated.     

Transport and Metabolism of the Tea Flavonoid (–)-Epicatechin by the Human Intestinal Cell Line Caco-2

Purpose: Tea flavonoids, including (–)-epicatechin (EC), have been suggested to have chemopreventive properties in cancer. However, there is limited knowledge of the oral bioavailability of these dietary compounds. The purpose of this study was to gain a better understanding of the absorption of EC. Methods: The intestinal epithelial membrane transport of EC was examined using the monolayer of the human Caco-2 cell line grown in Transwells, a common model of intestinal absorption. EC and its metabolites were measured by high performance liquid chromatography with diode array detection. Results: EC showed no apical to basolateral absorption at concentrations ranging from 5 to 50 M. In contrast, EC demonstrated basolateral to apical efflux with a P _app value of 0.67 ± 0.05 × 10^–6 cm/sec, i.e., slightly higher than for mannitol, 0.50 ± 0.30 × 10^–6 cm/sec, a paracellular transport marker. There was a 50% reduction in the efflux of EC in the presence of 50 M MK-571, a competitive inhibitor of the MRP2 transporter expressed in the apical membrane of Caco-2 cells. Most important, the presence of 50 M MK-571 resulted in clearly measurable apical to basolateral absorption of EC with a P _app of 0.31 ± 0.06 × 10^–6 cm/sec. Two polar metabolites, M1 and M2, were formed from EC, both of which appeared exclusively on the apical side. MK-571 (50 M) dramatically inhibited the transport for both of these metabolites. Incubations with inorganic ³⁵SO₄ ^2– and hydrolysis by aryl sulfatase strongly suggested that these metabolites were sulfate conjugates. Conclusions: These results suggest an important role for the multispecific organic anion transporter MRP2 in the bioavailability of EC and possibly other tea flavonoids.     

Successful chemoimmunotherapy of murine L1210 lymphatic leukemia with cyclophosphamide and mafosfamide-treated leukemia cells

Summary Balb/c × DBA/2 F₁ mice (CD2F₁ mice) bearing L1210 lymphatic leukemia (10 L1210 cells i.p. injected on day 0) were subjected to chemoimmunotherapy. They received 100 mg/kg of cyclophosphamide i.p. on day + 8 and 10⁶ or 10⁷ immunogenic L1210 cells treated in vitro with mafosfamide — ASTA Z7654 (L1210-Maf cells) i.p. or i.p. + s.c. on days 0, + 3, + 6, + 9, + 12 after the leukemia implantation.About 30% of leukemia-bearing mice receiving cyclophosphamide and L1210-Maf cells after L1210 inoculation were able to reject the leukemia (as compared with 0% after injection of L1210-Maf cells only or 5% after cyclophosphamide administration). Better results (54% of cured mice) were obtained if 10⁷ L1210-Maf cells were injected i.p. + s.c. beside cyclophosphamide. Biological response modifiers (BRM's): levamisole, BCG, bestatin did not improve these results in the doses used in the experiment.Augmentation of anti-L1210 therapeutic response is dependent on the administration of cyclophosphamide and L1210-Maf cels. Cyclophosphamide not only reduces the tumor burden but probably can potentiate the L1210-Maf dependent antitumor immunity as well.     

Transport of HIV-protease inhibitors across 1 alpha,25di-hydroxy vitamin D3-treated Calu-3 cell monolayers: modulation of P-glycoprotein activity

Purpose. The presence of P-glycoprotein (P-gp) within the lipid bilayers of the absorptive cells greatly influences drug entry into the HIV-infected sanctuary sites. The objective of this study was to access the potential role of pulmonary cells expressing high levels of P-gp in the efflux of potent anti-HIV drugs such as protease inhibitors. Methods. Human airway epithelium-derived Calu-3 cells grown in the presence of 0.025 mM 1,25di-hydroxy Vitamin D₃ (di-OH vit D₃) were used as a model to evaluate the effects of p-glycoprotein efflux of HIV protease inhibitors. Cells used as controls were not treated with di-OH vit D₃. The anti-HIV agents ³H Ritonavir and Saquinavir (50 M) were used as model compounds for influx and efflux studies. Results. Di-OH vit D₃ treatment enhanced the differentiation of Calu-3 cells indicated by more cilia and mucus secretion. It also caused elevated P-gp expression as demonstrated by Western Blot analysis and enhanced basal to apical transport of cyclosporine as compared with untreated cells. The amount of Saquinavir transported, after 3 h, across untreated Calu-3 cells (A-B) was 3-fold higher (1.62 g; Papp = 2.4 (± 0.79) × 10^–6 cm/s) than di-OH vit D₃-treated cells (0.57 g with the Papp = 5.02 (± 0.62) × 10^–7 cm/s). Similar transport profiles were obtained for ³H ritonavir and a significant increase (p < 0.05) in the A-B transport (2.5-fold) of ³H ritonavir was observed when the cell monolayers were preincubated with testosterone prior to transport studies. However, transport of AZT remained unaltered in di-OH vit D₃ treated monolayers. Conclusion. Modulation of P-gp activity may be necessary to increase the therapeutic efficacy of protease inhibitors against HIV-1 reservoirs across alveolar lining cells and fluids.     

Activation of recombinant h 5-HT1B and h 5-HT1D receptors stably expressed in C6 glioma cells produces increases in Ca2+-dependent K+ current

The putative coupling between stably expressed recombinant h 5-HT_1B or h 5-HT_1D receptors and K⁺ channels which regulate excitability was investigated in C6 glioma cells. Outward K⁺ currents (I _K) were examined in non-transfected C6 glioma cells and in cells expressing cloned h 5-HT_1B or h 5-HT_1D receptors using the patch-clamp technique in the whole-cell configuration. I _K was elicited by a depolarizing step from a holding potential of –60 mV. In C6 glioma cells expressing either recombinant h 5-HT_1B or h 5-HT_1D receptors, sumatriptan similarly increased I _K in a concentration-dependent manner (maximum increase 19.4±7.2%, n=8, P<0.05 and 25.1±3.9%, n=6, P<0.001, respectively) with EC₅₀ values (geometric mean with 95% confidence intervals in parentheses) of 56.3 nM (7.9–140 nM) and 68.7 nM (16–120 nM), respectively. Sumatriptan failed to elicit increases in I _K in non-transfected cells, confirming a specific involvement of the respective membrane h 5-HT_1B and h 5-HT_1D receptors in transfected C6 cells. In the presence of the mixed 5-HT_1B/D receptor antagonist GR 127935 (0.1 μM), sumatriptan (1 μM) failed to significantly increase I _K in C6 cells expressing h 5-HT_1B receptors (–7.5±3.5%, P=NS, n=6), although a higher concentration of GR 127935 (1 μM) was required to significantly inhibit sumatriptan-evoked increases in I _K in C6 cells expressing h 5-HT_1D receptors (–1.8±3.5%, P=NS, n=6), confirming that sumatriptan-evoked responses were indeed mediated by h 5-HT_1B and h 5-HT_1D receptors, respectively. In C6 cells expressing either cloned h 5-HT_1B or h 5-HT_1D receptors, sumatriptan-induced increases in I _K were prevented by the calcium chelator EGTA (5 mM) when included in the patch pipette (maximum increase 0.57±0.6%, n=3, P=NS and –2.8±1.6%, n=5, P=NS, respectively). In C6 cells expressing cloned h 5-HT_1B receptors, sumatriptan (1 μM) similarly failed to significantly increase I _K in the presence of dibutyryl cAMP (10 μM) or when a nominally Ca²⁺-free medium was included in the patch pipette (–19.4±5.1%, n=5 and –5.2±4.3%, n=5, respectively, P=NS in each case). In addition, the Ca²⁺-dependent K⁺ channel blockers iberiotoxin (0.1 μM) and tetraethylammonium (TEA, 1 mM) abolished sumatriptan-induced increases in I _K (–0.5±1.0%, n=4 and –3.9±3.1%, n=4, respectively, P=NS in each case) in C6 cells expressing h 5-HT_1B receptors, confirming the involvement of Ca²⁺-dependent K⁺ channels. In C6 cells expressing cloned h 5-HT_1B receptors, sumatriptan (1 μM) similarly failed to significantly increase I _k after 30-min incubation with thapsigargin (1 μM) or when heparin (2 mg/ml) was included in the patch pipette (1.1±0.4%, n=5 and 1.2±2.4%, n=5, respectively, P=NS). In conclusion, evidence is provided that both recombinant h 5-HT_1B and h 5-HT_1D receptors stably transfected in C6 glioma cells are positively coupled to Ca²⁺-dependent K⁺ channels, and the outward hyperpolarizing current mediated by these channels is dependent upon IP₃ receptor-mediated intracellular Ca²⁺ release. Received: 15 April 1998 / Accepted: 9 September 1998     

Regulation of 1‐α, 25‐Dihydroxyvitamin D3 on Interleukin‐6 and Interleukin‐8 Induced by Sulfur Mustard (HD) on Human Skin Cells*

Abstract: The regulatory effects of the active form of vitamin D, 1‐α, 25‐dihydroxyvitamin D₃ (1‐α, 25 (OH)₂D₃) were assessed on the cytokine and chemokine secretion induced by sulfur mustard on human skin fibroblasts and human epidermal keratinocytes. Stimulation of human skin fibroblasts with sulfur mustard (10^?4 M for 24 hr at 37°) resulted in approximately a 5 times increase in the secretion of interleukin‐6 and over a 10 times increase for interleukin‐8, which was inhibited by 1‐α, 25 (OH)₂D₃, at ≤10^?9 M. 1‐α, 25 (OH)₂D₃ also suppressed interleukin‐8 secretion by 5 times and interleukin‐6 by 4 times on sulfur mustard‐stimulated human epidermal keratinocytes at concentrations ≤ 10^?9 M. The effect of 1‐α, 25 (OH)₂D₃ was dose‐dependent for the suppression of interleukin‐6 and interleukin‐8 induced by sulfur mustard on human skin fibroblasts/human epidermal keratinocytes, apparent at nanomolar concentrations. Our results indicate that the suppression of these inflammatory mediators by 1‐α, 25 (OH)₂D₃ is dependent on the source of the primary cultures, cell densities, and kinetics of pretreatments. In contrast to the inhibition of cytokine/chemokine production, cell proliferation was enhanced by almost 1.7 times on treated human epidermal keratinocytes with 1‐α, 25 (OH)₂D₃ (1×10^?9 M) after sulfur mustard‐stimulation (10^?4 M for 24 hr at 37°C). The observed enhancement diversified based on cell density, and kinetics of pretreatment with a maximal synergism (s) observed at 1×10^?9 M. Photomicrographs show typical signs of cellular degeneration caused by sulfur mustard such as chromatin condensation. The observed cellular degeneration was lessened when human epidermal keratinocytes were treated with 1‐α, 25 (OH)₂D₃ (2×10^?9 M). 1‐α, 25(OH)₂D₃ could be an alternative treatment for cutaneous inflammation disorders caused by sulfur mustard because we have demonstrated its ability to suppress inflammatory mediators and enhanced cell proliferation in human skin cells stimulated with sulfur mustard.     

组胺H2受体激动剂和拮抗剂及抗癌药对正常人造血祖细胞和HL-60白血病细胞生长的作用

采用体外微量克隆培养体系研究了组胺H2受体激动剂4-甲基组胺(4-MH)和拮抗剂雷尼替叮(ranitidine)及抗癌药阿糖胞苷分别对正常人外周血粒-巨噬系祖细胞(PBCFU-GM)和HL-60白血病细胞生长的作用。当4-MH的浓度为10^-9～10^-6mol·L^-1时,可促进PBCFU-GM的增殖,4-MH的浓度增加至10^-4mol·L^-1时则表现为抑制PBCFU-GM的增殖。Ranitidine的浓度为10^-9～10^-5mol·L^-1时,表现出对PBCFU-GM增殖的抑制作用,但在10-6mol·L^-1剂量时对PBCFU-GM的抑制率低于50%,而在该剂量时对HL-60白血病细胞的抑制率已达100%,具有一定的选择性。抗癌药阿糖胞苷(Ara-C)对HL-60白血病细胞的抑制作用比对PBCFU-GM的抑制作用较强,但两者的IC₅₀值处于同一个数量级。在强化化疗剂量10^-5mol·L^-1时,Ara-C对HL-60白血病细胞和PBCFU-GM正常造血祖细胞的抑制率均达100%。     

小鼠造血干细胞和P388白血病干细胞对5种抗癌药的敏感性比较

用脾集落形成法比较了5种抗癌药对小鼠造血干细胞(NCFU-S)和P₃₈₈白血病干细胞(LCFU-S)的作用。三尖杉酯碱、半合成三尖杉酯碱、高三尖杉酯碱和环磷酰胺对两类干细胞作用的剂量—反应曲线呈指数形,效能比依次为5.15,6.01,7.96和9.98。阿糖胞苷对NCFU-S无明显作用,但对LCFU-S杀伤作用强,大剂量时剂量—反应曲线趋于水平。当三尖杉酯碱、高三尖杉酯碱和半合成三尖杉酯碱的剂量分别低于0.30,0.28和0.75mg/kg时,对LCFU-S无明显作用,剂量—反应曲线上出现“肩形”,提示LCFU-S在小剂量三尖杉酯类生物碱作用下,有一受亚致死性损伤后修复过程。     

Acute and chronic dose/response effects of inhaled benzene on multipotential hematopoietic stem (CFU-S) and granulocyte/macrophage progenitor (GM-CFU-C) cells in CD-1 mice

Many blood dyscrasias are associated with hematopoietic stem cell anomalies. In order to investigate the interaction of inhaled benzene with hematopoietic stem cells, marrow and spleen cells from male CD-1 mice were assayed for CFU-S by the spleen colony method, and for GM-CFU-C by an in vitro agar technique following benzene exposure using a number of regimes. Specifically, these consisted of a 6 hr/day × 5 days exposure to either 1.1, 9.9, 103, 306, 603, 1276, 2416, or 4862 ppm (Experiment 1); a 6 hr/day × 5 days/week × 50 days exposure to 9.6 ppm (Experiment 2); and a 6 hr/day × 5 days/week × 26 weeks exposure to 302 ppm (Experiment 3). In Experiment 1 femoral and splenic cellularites were significantly reduced at concentrations ≥ 103 ppm. Marrow concentration of GM-CFU-C was equivalent to or greater than control values at all levels, however, splenic GM-CFU-C concentration was decreased at 103 ppm and above. Femoral and splenic CFU-S and GM-CFU-C per organ were depressed at 103 ppm and above. No change in colony/cluster ratio was observed. Since changes in stem cell number were detected at 100 ppm, Experiment 2 was designed to compare the effects of a 10-ppm exposure delivered over 50 days with the 100-ppm exposure delivered over 5 days. In Experiment 2, no detectable changes were observed in bone marrow, but splenic cellularity and the number and concentration of splenic CFU-S were elevated vs matched control. Experiment 3 repeated a regime that produced two cases of myeloid leukemia in CD-1 mice and a marked depression was observed in marrow and spleen cellularity. The concentration and number of marrow and spleen CFU-S and marrow GM-CFU-C were also depressed. The number of splenic GM-CFU-C were also reduced, however, splenic GM-CFU-C concentration was increased relative to control. Splenic colony/cluster ratio was also significantly reduced in this experiment. These data demonstrate that 5-day inhalation exposure to benzene concentrations 10 times the current TLV depresses marrow and splenic CFU-S and GM-CFU-C with splenic cells showing greater sensitivity. Stem cell depletion seems, therefore, to be involved in the pathogenesis of benzene-induced hematotoxicity.     

Organic Cation Transport in Rabbit Alveolar Epithelial Cell Monolayers

Purpose. To characterize organic cation (OC) transport in primary cultured rabbit alveolar epithelial cell monolayers, using [^l4C]-guanidine as a model substrate. Methods. Type II alveolar epithelial cells from the rabbit lung were isolated by elastase digestion and cultured on permeable filters pre-coated with fibronectin and collagen. Uptake and transport studies of [¹⁴C]-guanidine were conducted in cell monolayers of 5 to 6 days in culture. Results. The cultured alveolar epithelial cell monolayers exhibited the characteristics of a tight barrier. [¹⁴C]-Guanidine uptake was temperature dependent, saturable, and inhibited by OC compounds such as amiloride, cimetidine, clonidine, procainamide, propranolol, tetraethyl-ammonium, and verapamil. Apical guanidine uptake (K_m = 129 ± 41 M, V_max = 718 ± 72 pmol/mg protein/5 min) was kinetically different from basolateral uptake (K_m = 580 ± 125 (M, V_max = 1,600 ± 160 pmol/mg protein/5 min). [¹⁴C]-Guanidine transport across the alveolar epithelial cell monolayer in the apical to basolateral direction revealed a permeability coefficient (P_app) of (7.3 ± 0.4) × 10^-7 cm/sec, about seven times higher than that for the paracellular marker [¹⁴C]-mannitol. Conclusions. Our findings are consistent with the existence of carrier-mediated OC transport in cultured rabbit alveolar epithelial cells.     

Analysis of Nonlinear Hepatic Clearance of a Cyclopentapeptide,BQ-123, with the Multiple Indicator Dilution Method Using the Dispersion Model

Purpose. To bridge in vitro, in situ and in vivo kinetic analyses of the hepatic clearance of a cyclopentapeptide, BQ-123, by using dispersion models that assume nonlinear pharmacokinetics. Methods. Rat livers were perfused by the multiple indicator dilution method with doses of BQ-123 ranging from 1-1000 g. The outflow dilution curves were fitted to a two-compartment dispersion model that was solved numerically by the finite difference method. Further, in vivo plasma concentrations of BQ-123 after bolus injection were analyzed with a hybrid physiological model that incorporates the hepatic dispersion model. Results. The calculated Michaelis-Menten constants (K_m = 12.0 M, V_max = 321 pmol/min/10⁶ cells, P_dif = 1.2 l/min/10⁶ cells) were comparable to those obtained previously from the in vitro isolated hepatocyte experiment (K_m = 9.5 M, V_max = 517 pmol/min/10⁶ cells, P_dif =1.1 l/min/10⁶ cells). The plasma concentrations of BQ-123 at doses of 1-25 mg/kg were explained well by the hybrid physiological model. Conclusions. These results suggest that carrier-mediated transport on the sinusoidal membrane was responsible for the in vivo hepatic elimination of BQ-123.     

Dynamics of Bromodeoxyuridine Incorporation into DNA of Squamous Carcinoma Cells During Mid and Late Logarithmic Growth

Head and neck squamous carcinoma cell lines, UM-SCC 1, 5, 9, 11B, and 14B, were exposed in vitro to bromodeoxyuridine (BUdR) during logarithmic growth to determine the effects of drug concentration (0.01 to 10 µM) and duration of exposure (3, 7, and 10 days) on cell growth and on incorporation of BUdR into DNA. Concentrations of less than 1.0 µM were not growth inhibitory except with UM-SCC-11B. After 10 days of exposure to 5 µM BUdR, survival fractions for all lines ranged from 2 to 65% of controls. Replacement of thymidine by BUdR in DNA was assessed by gas chromatography/mass spectroscopy. Percentage replacement (% R) was described by the equation % R = 100 (C/t)^s/[(C/t)₅₀ ^s + (C/t)^s], where C is the concentration of BUdR (µM), t is the time in days, s is a constant, and (C/t)₅₀ is a constant corresponding to % R = 50%. BUdR incorporation reached a time-and concentration-dependent maximum that, after 3 to 7 days of culture in 10 µM BUdR, ranged from 30 to 60% R. Subsequently, % R declined with time even though the cells were fed daily with fresh BUdR-containing medium.     

α2-Adrenoceptor mediated inhibition of forskolin-stimulated cyclic AMP accumulation in isolated porcine palmar lateral veins

The aim of this study was to use a ³H-adenine pre-labelling technique to characterise the effect of ₂-adrenoceptor activation on forskolin-stimulated cyclic AMP accumulation in the isolated porcine palmar lateral vein. Forskolin (10^–7–10^–4 M) stimulated ³H-cyclic AMP accumulation in the isolated porcine palmar lateral vein in a biphasic and concentration-dependent manner. In the absence of the cyclic AMP-selective phosphodiesterase inhibitor rolipram, forskolin stimulated ³H-cyclic AMP accumulation approximately 7–8 fold. The response reached a peak after 5 min. In the presence of rolipram (10^–5 M), basal ³H-cyclic AMP levels were approximately 70% higher than in its absence (basal: 1823 ± 57 dpm; rolipram: 3088 ± 229, n \2 = 3) and forskolin (3 × 10^–5 M) stimulated ³H-cyclic AMP accumulation approximately 8 fold. The latter response reached a plateau 10 min after the addition of forskolin. In all subsequent studies, the tissues were incubated with forskolin (3 × 10^–5 M) for 5 min in the absence of rolipram. Noradrenaline (NA; 10^–9–10^–4 M) and UK14304 (10^–9–10^–4 M) inhibited forskolin-stimulated ³H-cyclic AMP accumulation in a concentration-dependent manner with mean pIC₅₀ values of 7.61 ± 0.37 (n \s = 4) and 7.76 ± 0.23 (n \s = 5), respectively. With either NA or UK14304, the maximal inhibition of the forskolin response obtained was approximately 75%. Neither NA (10^–4 M) nor UK14304 (10^–4 M) altered basal ³H-cyclic AMP levels. Phenylephrine (10^–4 M) had no effect on basal ³H-cyclic AMP levels and produced a 25.4 ± 7.1% inhibition of the forskolin-stimulated response, an effect that was reversed by 10^–6 M rauwolscine. Rauwolscine (10^–9–10^–6 M) produced a concentration-dependent reversal of the inhibitory effect of UK14304 10^–6 M on forskolin-stimulated ³H-cyclic AMP accumulation with a mean pK _i of 8.35 ± 0.39 (n = 3), but had no effect on basal or on forskolin-stimulated ³H-cyclic AMP levels. Similarly, prazosin (3 × 10^–8–3 × 10^–5 M) or imiloxan (3 × 10^–8––3 × 10^–5 M) produced a concentration-dependent reversal of the UK14304 (10^–7 M)-induced inhibition of forskolin-stimulated ³H-cyclic AMP accumulation, with mean pK _i values of 6.32 ± 0.22 (n = 4) and 6.01 ± 0.30 (n = 3), respectively; neither drug had any effect on basal or on forskolin-stimulated ³H-cyclic AMP levels. This suggests that the receptor is of the _2A-adrenoceptor subtype. It can be seen from these studies that it is possible to measure changes in cyclic AMP accumulation in porcine vascular smooth muscle using a pre-labelling technique, and it has been possible to demonstrate the presence of functional ₂-adrenoceptors, stimulation of which results in inhibition of forskolin-stimulated cyclic AMP formation.