Biomedical subjects

X F Zhang

Publications and source records attributed to X F Zhang.

At least 19 recordsLinked to original sources

PubMed2006

Novel magnetic rings for rapid vascular reconstruction in canine liver transplantation model.

OBJECTIVE: Magnetic rings were used for rapid vascular reconstruction in a canine liver transplantation model. MATERIALS AND METHODS: Thirty-two adult mongrel dogs weighing 13 to 16 kg were randomly selected as donors or recipients of transplantations. The recipients were randomly divided into two groups: group A (n = 10) had magnetic rings used for vascular reconstruction without venovenous bypass; group B (n = 6) had vascular reconstruction performed by continuous suturing with splenojugular venovenous bypass. RESULTS: In group A, the entire operative period was 3.24 +/- 0.49 hours, the durations of clamping the portal vein and the infrahepatic vena cava of the recipient were 5.89 +/- 2.27 minutes and 3.89 +/- 0.73 minutes, respectively. In group B, the entire operative period was 4.12 +/- 0.51 hours with the duration of clamping portal vein and infrahepatic vena cava, 28.33 +/- 6.04 minutes and 12.16 +/- 3.72 minutes (P < .01 vs group A). In group A, mean arterial pressure dropped during the anhepatic phase but recovered quickly after reperfusion. The fluid infusion was about 730.56 +/- 50.56 mL in the group A and a pressor agent was unnecessary. In group B, blood pressure dropped during the anhepatic phase and slowly recovered. The fluid infusion was about 2241.67 +/- 390.78 mL and a pressor agent was used to maintain the blood pressure of the recipient. No twist or thrombus was discovered in the anastomoses group A and the endothelium at the site of anastomosis was entire. In group B, errhysis was common in the anastomotic stomas. Nine of 10 dogs in group A survived more than 3 days, the longest being 8 days, whereas four of the six dogs in group B survived less than 3 days. CONCLUSION: The results showed that the anhepatic time was significantly shortened (about 5.89 +/- 2.27 minutes) in group A compared with group B and venovenous bypass was unnecessary. Magnetic rings could be used for rapid vascular reconstruction in canine liver transplantation model. The long-term results of this procedure should be clarified before it is applied in clinical practice in the future.

Animals↗

PubMed2005

Traditional Chinese medicine Bao Gan Ning increase phosphorylation of CREB in liver fibrosis in vivo and in vitro.

Previous studies have demonstrated that traditional Chinese medicine Bao Gan Ning, which contains six different drugs: Trionyx sinensis Wiegmann shell, Prunus persica (L.) Batsch seed, Salvia miltiorrhiza Bge. root, Mallotus opelta (Lour.) Muell-Arg root, Astragalus membranaceus (Fisch.) Bge. var. mongho-licus (Bge.) Hsiao root and Scutellaria baicalensis Georgi root, was able to protect liver against fibrosis in CCL4 models. In an effort to elucidate molecular mechanisms by which Bao Gan Ning exerts its anti-fibrosis activity, effects of Bao Gan Ning on liver fibrosis and cAMP response element binding protein (CREB), an important transcription factor involved in liver fibrosis, were evaluated in animal and cell models in this work. Results showed that Bao Gan Ning (2.16 or 4.32 g/kg/day) significantly decreased alanine aminotransferase (ALT) and hyaluronidase levels and reversed liver fibrosis in rat liver fibrosis models. The proliferation of HSC-T6, a hepatic stellate cell line, was also significantly inhibited by incubation with serums that were prepared from rats fed with Bao Gan Ning. Most interestingly, results from Western blot, immunohistochemistry and electrophoretic mobility shift assay (EMSA) showed that Bao Gan Ning up-regulated CREB phosphorylation both in rat liver fibrosis models and in HSC-T6 cells, but did not affect protein level of CREB and the DNA binding activity of CREB. These results suggested that up-regulation of CREB phosphorylation may be involved in anti-fibrosis activity of Chinese medicine Bao Gan Ning.

Animals↗

PubMed2002

Properties and biocompatibility of chitosan films modified by blending with PEG.

Chitosan (beta-1,4-D-glucosamine), a polysaccharide with excellent biological properties, has been widely used in biomedical fields, but many barriers still exist to its broader usage due to its chemical and physical limitations. Further work is needed to improve these properties, but changes of the chemical and physical properties will influence its biocompatibility, so the biological attribute of modified chitosan must be evaluated. In this study, the biocompatibility of chitosan modified by several methods was carefully evaluated at the cellular and protein levels using different physical and biological methods. The results provide a theoretical basis for screening biomaterials. We studied the properties of five kinds of materials made by blending chitosan with different types of polyethylene glycol (PEG). The properties included physical and chemical properties, such as mechanical strength, static contact angle, spectroscopy, thermodynamic attributes and so on. The mechanical properties were slightly improved with the proper amount of PEG, but the improvement was not obvious and was destroyed by the wrong proportion of PEG. Cultures of the cells and amounts and structures of the adsorbed proteins on different materials showed that the PEG effectively improved the biocompatibility of the materials. The PEG enhanced the protein adsorption, cell adhesion, growth and proliferation, but the effects were impaired by excessive PEG. The experiments also demonstrated that the optimum PEG concentration helped to maintain the natural structure of the protein adsorbed on the materials and that maintaining the natural structure benefited cell growth. Analysis of the results based on the intramolecular and intermolecular interaction forces leads to a basic theory for the modification of biomaterials.

3T3 Cells↗

PubMed2002

Energy dispersive spectroscopy analysis of aluminium segregation in silicon carbide grain boundaries.

The aluminium distribution in polycrystalline SiC hot-pressed with aluminium, boron and carbon additives was studied using X-ray energy-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The Al excess in homophase SiC grain boundary films was determined, taking into account dissolved Al in the SiC lattice. In the spot-EDS analysis, an electron beam probe with a calibrated diameter was formed, and the total beam-specimen interaction volume was defined, taking the beam spreading through crystalline TEM foil into consideration. EDS spectra were collected from regions containing intergranular films and adjacent matrix grains, respectively. A theoretical treatment was presented and experimental errors were estimated, with a further discussion about the effects of foil thickness. Experimental examples are given, followed by statistical EDS analyses for grain boundary films in SiC samples hot-pressed with increased amounts of Al additions. The results demonstrated a substantial Al segregation in the nanometer-wide intergranular films in all samples. Al additions higher than 3 wt% saturated the Al concentrations in SiC grains and in grain boundary films. The effect of foil thickness, and the parameters for determining the optimum incident beam diameter in the EDS analysis are discussed.

Journal Article↗

PubMed2001

Epibatidine, a nicotinic acetylcholine receptor agonist, inhibits the capsaicin response in dorsal root ganglion neurons.

In patch-clamp recordings from small-medium diameter dorsal root ganglion neurons in culture, (+/-)-epibatidine (1 microM) was able to inhibit the capsaicin response (IC(50)=0.32 microM) in neurons where there was no detectable direct nicotinic response. Thus, (+/-)-epibatidine may inhibit the vanilloid receptor in a manner that is not dependent upon nicotinic current activation, representing another mechanism by which such ligands could modulate vanilloid receptor signaling.

Animals↗

PubMed2001

Stimulation of beta 1 integrin induces tyrosine phosphorylation of vascular endothelial growth factor receptor-3 and modulates cell migration.

Interactions between integrins and tyrosine kinase receptors can modulate a variety of cell functions. We observed a cooperative interaction between the beta(1) integrin and vascular endothelial growth factor receptor-3 (VEGFR-3 or Flt4) that appeared to be required for cell migration. By using VEGFR-3-transfected 293 cells (293/VEGFR-3) or primary dermal microvascular endothelial cells (DMEC), we found that stimulation with either soluble or immobilized extracellular matrix (ECM) proteins, collagen or fibronectin (FN), resulted in the increased tyrosine phosphorylation of VEGFR-3 in the absence of a cognate ligand. This increased tyrosine phosphorylation of VEGFR-3 was diminished by pretreatment with a blocking antibody against the beta(1) integrin. Cross-linking with anti-beta(1) integrin antibody induced a similar degree of tyrosine phosphorylation of VEGFR-3. Stimulation with collagen or FN induced an association between beta(1) integrin and VEGFR-3 in both 293/VEGFR-3 and primary DMEC cells. Collagen or FN-induced tyrosine phosphorylation of VEGFR-3 was inhibited by treatment with cytochalasin D, an inhibitor of actin polymerization. Collagen or FN was able to induce the migration of 293/VEGFR-3 or DMEC cells to a limited extent. However, migration was dramatically enhanced when a gradient of the cognate ligand, VEGF-D, was added. VEGF-D failed to induce cell migration in the absence of ECM proteins. Introducing a mutation at the kinase domain of VEGFR-3 or treatment with blocking antibody against either VEGFR-3 or beta(1) integrin inhibited cell migration induced by ECM and VEGF-D, indicating that signals from both beta(1) integrin and VEGFR-3 are required for this cell function.

Cell Movement↗

PubMed2001

Quenching quorum-sensing-dependent bacterial infection by an N-acyl homoserine lactonase.

Bacterial cells sense their population density through a sophisticated cell-cell communication system and trigger expression of particular genes when the density reaches a threshold. This type of gene regulation, which controls diverse biological functions including virulence, is known as quorum sensing. Quorum-sensing signals, such as acyl-homoserine lactones (AHLs), are the essential components of the communication system. AHLs regulate virulence gene expression in a range of plant and animal (including human) bacterial pathogens. AHL-producing tobacco restored the pathogenicity of an AHL-negative mutant of Erwinia carotovora. Different bacterial species may produce different AHLs, which vary in the length and substitution of the acyl chain but contain the same homoserine lactone moiety. Here we show that the acyl-homoserine lactonase (AHL-lactonase), a new enzyme from Bacillus sp., inactivates AHL activity by hydrolysing the lactone bond of AHLs. Plants expressing AHL-lactonase quenched pathogen quorum-sensing signalling and showed significantly enhanced resistance to E. carotovora infection. Our results highlight a promising potential to use quorum-sensing signals as molecular targets for disease control, thereby broadening current approaches for prevention of bacterial infections.

4-Butyrolactone↗

PubMed2001

Janus kinase 2 is involved in stromal cell-derived factor-1alpha-induced tyrosine phosphorylation of focal adhesion proteins and migration of hematopoietic progenitor cells.

Stromal cell-derived factor-1 (SDF-1), the ligand for the CXCR4 receptor, is a highly efficacious chemoattractant for CD34(+) hematopoietic progenitor cells. However, the SDF-1/CXCR4 signaling pathways that regulate hematopoiesis are still not well defined. This study reports that SDF-1alpha can stimulate the tyrosine phosphorylation of Janus kinase 2 (JAK2) and other members of the JAK/signal transduction and activation of transcription (STAT) family, including JAK1, tyrosine kinase 2, STAT2, and STAT4 in the human progenitor cell line, CTS. SDF-1alpha stimulation of these cells also enhanced the association of JAK2 with phosphatidylinositol 3 (PI3)-kinase. This enhanced association was abolished by pretreatment of cells with AG490, a specific JAK2 inhibitor. Furthermore, pretreatment of CTS cells with AG490 significantly inhibited SDF-1alpha-induced PI3-kinase activity, and inhibition of JAK2 with AG490 ablated the SDF-1alpha-induced tyrosine phosphorylation of multiple focal adhesion proteins (including focal adhesion kinase, related adhesion focal tyrosine kinase, paxillin, CrkII, CrkL, and p130Cas). Chemotaxis assays showed that inhibition of JAK2 diminished SDF-1alpha-induced migration in both CTS cells and CD34(+) human bone marrow progenitor cells. Hence, these results suggest that JAK2 is required for CXCR4 receptor-mediated signaling that regulates cytoskeletal proteins and cell migration through PI3-kinase pathways in hematopoietic progenitor cells. (Blood. 2001;97:3342-3348)

Adaptor Proteins, Signal Transducing↗

PubMed2001

Immunization of metastatic breast cancer patients with a fully synthetic globo H conjugate: a phase I trial.

The carbohydrate antigen globo H commonly found on breast cancer cells is a potential target for vaccine therapy. The objectives of this trial were to determine the toxicity and immunogenicity of three synthetic globo H-keyhole limpet hemocyanin conjugates plus the immunologic adjuvant QS-21. Twenty-seven metastatic breast cancer patients received five vaccinations each. The vaccine was well tolerated, and no definite differences were observed among the three formulations. Serologic analyses demonstrated the generation of IgM antibody titers in most patients, with minimal IgG antibody stimulation. There was significant binding of IgM antibodies to MCF-7 tumor cells in 16 patients, whereas IgG antibody reactivity was observed in a few patients. There was evidence of complement-dependent cytotoxicity in several patients. Affinity column purification supported the specificity of IgM antibodies for globo H. On the basis of these data, globo H will constitute one component of a polyvalent vaccine for evaluation in high-risk breast cancer patients.

Adult↗

PubMed2001

Failure of endothelin-1 to activate store-operated Ca2+ channels by lack of mobilization from intracellular Ca2+ stores in cultured bovine adrenal chromaffin cells.

We have recently shown that in addition to L-type voltage-operated Ca2+ channel (VOC), endothelin-1 (ET-1) stimulation opens two types of Ca2+-permeable nonselective cation channels [designated nonselective cation channel-1 (NSCC-1) and NSCC-2]. However, in this Ca2+ entry, the involvement of store-operated Ca2+ channel (SOCC), which is suggested to exist in chromaffin cells, was unclear. Those NSCCs as well as SOCC can be pharmacologically discriminated using Ca2+ channel blockers such as SK&F 96365 and LOE 908. To clarify whether SOCC should actually exist and play a role in Ca2+ entry in chromaffin cells stimulated with ET-1, we examined the effects of removal of extracellular Ca2+, thapsigargin (TG, an inhibitor of endoplasmic reticulum Ca2+-ATPase), LOE 908 and SK&F 96365 on cytosolic free Ca2+ concentrations ([Ca2+]i) in cultured bovine adrenal chromaffin cells. After the cells were exposed to Ca2+-free medium followed by exposure to TG to deplete Ca2+ from the intracellular Ca2+ store, restoration of extracellular Ca2+ caused a gradual increase in [Ca2+]i (to about 200% of control). The increase was unaffected by LOE 908, but completely abolished by SK&F 96365. In the Ca2+-free medium, no increase in [Ca2+]i by ET-1 was observed, but the subsequent restoration of extracellular Ca2+ induced a rapid increase in [Ca2+]i (to the same level of [Ca2+]i as that evoked by ET-1 in the normal medium (1.0 mM Ca2+)). Since SK&F 96365 is also a blocker of SOCC, these results indicate that in bovine adrenal chromaffin cells, Ca2+ entry through SOCC (Ca2+ influx through the capacitative Ca2+ entry system) occurs but is comparably weak, and that it virtually does not work on the stimulation of ET-1.

Acetamides↗

PubMed2001

Phylogenetic relationships of Anaplasma marginale and 'Ehrlichia platys' to other Ehrlichia species determined by GroEL amino acid sequences.

The heat-shock protein (GroEL) genes of Anaplasma marginale, Ehrlichia muris and 'Ehrlichia platys' were sequenced and compared with the GroEL of other species of Ehrlichia. The GroEL amino acid sequences of A. marginale and 'E. platys' were most similar to the GroEL sequence of Ehrlichia phagocytophila, with which they formed one group with 6-10% divergence. The E. muris GroEL was most closely related to the GroEL of two unclassified strains (HF-565 and Anan), then to Ehrlichia chaffeensis, Ehrlichia canis, Ehrlichia ewingii and Cowdria ruminantium, forming a second distinct group (0.3-8.6% divergence). The GroELs of Ehrlichia risticii and Ehrlichia sennetsu were very similar to one another (only 2% divergence), forming the third group. The first two groups were relatively closely related (17-20% divergence), while the third group was only distantly related to the first two groups (62-73% divergence).

Amino Acid Sequence↗

PubMed2001

Ras activation of the Raf kinase: tyrosine kinase recruitment of the MAP kinase cascade.

A continuing focus of our work has been an effort to understand the signal transduction pathways through which insulin achieves its cellular actions. In the mid-1970s, we and others observed that insulin promoted an increase in Ser/Thr phosphorylation of a subset of cellular proteins. This finding was unanticipated, inasmuch as nearly all of the actions of insulin then known appeared to result from protein dephosphorylation. In fact, nearly 15 years elapsed before any physiologic response to insulin attributable to stimulated (Ser/Thr) phosphorylation was established. Nevertheless, based on the hypothesis that insulin-stimulated Ser/Thr phosphorylation reflected the activation of protein (Ser/Thr) kinases downstream of the insulin receptor, we sought to detect and purify these putative, insulin-responsive protein (Ser/Thr) kinases. Our effort was based on the presumption that an understanding of the mechanism for their activation would provide an entry into the biochemical reactions through which the insulin receptor activated its downstream effectors. To a degree that, in retrospect, is surprising, this goal was accomplished, much in the way originally envisioned. It is now well known that receptor tyrosine kinases (RTKs) recruit a large network of protein (Ser/Thr) kinases to execute their cellular programs. The first of these insulin-activated protein kinase networks to be fully elucidated was the Ras-Raf-mitogen-activated protein kinase (MAPK) cascade. This pathway is a central effector of cellular differentiation in development; moreover, its inappropriate and continuous activation provides a potent promitogenic force and is a very common occurrence in human cancers. Conversely, this pathway contributes minimally, if at all, to insulin's program of metabolic regulation. Nevertheless, the importance of the Ras-MAPK pathway in metazoan biology and human malignancies has impelled us to an ongoing analysis of the functions and regulation of Ras and Raf. This chapter will summarize briefly the way in which work from this and other laboratories on insulin signaling led to the discovery of the mammalian MAP kinase cascade and, in turn, to the identification of unique role of the Raf kinases in RTK activation of this protein (Ser/Thr) kinase cascade. We will then review in more detail current understanding of the biochemical mechanism through which the Ras proto-oncogene, in collaboration with the 14-3-3 protein and other protein kinases, initiates activation of the Raf kinase.

14-3-3 Proteins↗

PubMed2001

[Fudenine, relative to blood glucose-control, is a novel membrane protein].

OBJECTIVE: To determine whether Fudenine is a novel membrane protein. METHODS: Green fluorescence protein(GFP) was used to localize Fudenine in vivo. GFP, as a control, was targeted to cytoplasm. Epithelial cell, CBRH7919, and non-epithelial cell, L-6TG, were cultured and transiently transfected by using the lipofectamine reagent. After 48 h, intact cells were examined with fluorescence microscope for Fudenine. RESULTS: Reporter plasmid pEGFP-N1, as a control, was expressed and localized to cytoplasm. But Fudenine, driven by the cytomegalovirus promoterenhancer contained in the pEGFP-N1 vector, was overexpressed and targeted to cellular membrane. CONCLUSIONS: Fudenine is a novel membrane protein. It may play the similar role with its homologues AC133 antigen and prominin in human and mouse, respectively. It might be involved in signaling transduction and regulate blood glucose metabolism in vivo.

AC133 Antigen↗

PubMed2000

A second generation synthesis of the MBr1 (globo-H) breast tumor antigen: new application of the n-pentenyl glycoside method for achieving complex carbohydrate protein linkages.

A new synthesis of the hexasaccharide MBr1 antigen (globo-H) is reported. A revised construction with improved efficiency was necessary because an anti-cancer vaccine containing this antigen is entering phase II and phase III clinical trials for prostate cancer. The key feature of this second generation synthesis is the preparation of globo-H as its n-pentenyl glycoside. This group serves as an anomeric protecting group and as a linker for bioconjugation to carrier protein. The resultant synthesis allows for the production of suitable quantities of globo-H for clinical trials.

Antigens, Neoplasm↗

PubMed2000

Polyclonal antibodies from patients immunized with a globo H-keyhole limpet hemocyanin vaccine: isolation, quantification, and characterization of immune responses by using totally synthetic immobilized tumor antigens.

We have previously reported on a carbohydrate-based vaccine program for immunotherapy in cancer patients. One such vaccine, based on the globo H antigen conjugated to the protein keyhole limpet hemocyanin (KLH), has been in clinical evaluation. Although this and other carbohydrate vaccines have been shown to induce antibody responses, there are currently no quantitative data on the antibody levels achieved in immunized patients by these or other anti-cancer vaccines. We report herein an efficient route to complex synthetic oligosaccharides attached to an affinity matrix for identifying and isolating antibodies elicited against such a carbohydrate-based vaccine in humans. Pre- and postvaccination profiles from serum samples of patients immunized with globo H-KLH were compared. All anti-globo H antibody activity was efficiently separated from other serum constituents. The isolated antibodies were readily quantified, and their specificities were analyzed. Since no comparable data were available on antibodies resulting from the vaccination of other cancer patients, we compared the observed levels with those quoted in studies with bacterial polysaccharide vaccines that had been quantified. Remarkably, cancer patients immunized with globo H-KLH produce anti-globo H antibody levels often exceeding those formed by immunization with bacterial polysaccharides. In addition, substantial quantities of both IgG and IgM antibodies were elicited, clearly indicating a class switch to IgG. Taken together, these analyses serve to clarify several aspects of the immune response to the vaccine and give several new insights to the carbohydrate-based vaccination strategy. Furthermore, antibodies so isolated could well have applications in clinical therapy.

Antibodies↗

PubMed2000

Adherence of human monocytes and NK cells to human TNF-alpha-stimulated porcine endothelial cells.

Discordant xenograft models undergoing delayed rejection response are characterized by xenograft infiltration with host monocytes and NK cells, associated with the release of large quantities of pro-inflammatory cytokines, such as TNF-alpha. In the present study, human monocytes (PBMo)/NK cells (PBNK) isolated from peripheral blood and cultured porcine aortic endothelial cells (PAEC) treated with recombinant human TNF-alpha (rhTNF-alpha) were used to investigate their adhesive interactions and mAbs against porcine E-selectin, human CD11a and CD49d were used to test their relative contributions to such intercellular adhesions. The PBMo exhibited significantly greater adherence to resting (unstimulated) PAEC than PBNK. The rhTNF-alpha upregulated E-selectin and vascular cell adhesion molecule-1 (VCAM-1) expression on PAEC and augmented the adhesiveness of PAEC for PBMo and PBNK in a time- and dose-dependent manner. In mAb blocking assays, anti-E-selectin, anti-CD11a and anti-CD49d mAbs did not inhibit PBMo adherence to rhTNF-alpha-stimulated PAEC when used singly, but resulted in a maximal inhibitory effect when used in combination. Regarding PBNK, anti-E-selectin mAb had no marked influence on PBNK adherence. The combined use of anti-CD11a and anti-CD49d mAbs produced additive reduction in the PBNK binding to rhTNF-alpha-stimulated PAEC, even to far below baseline (unstimulated) levels. Therefore, it is concluded that human TNF-alpha promotes the adhesiveness of PAEC for human monocytes and NK cells and that the mechanism underlying the increased adherence differs for PBMo and PBNK.

Animals↗

PubMed2000

Endothelin-1-induced contraction of rat thoracic aorta depends on calcium entry through three types of calcium channel.

We have recently shown that endothelin-1 (ET-1) activates two types of Ca2+-permeable nonselective cation channels (designated NSCC-1 and NSCC-2) and store-operated Ca2+ channel (SOCC). These channels can be pharmacologically discriminated using 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1-H-imidazoe l hydrochloride (SK&F 96365) (a blocker of NSCC-2 and SOCC) and (RS)-(3,4-dihydro-6,7-dimethoxyisoquinoline-1-gamma l)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxyphenyl)ethyl]acetamide (LOE 908) (a blocker of NSCC-1 and NSCC-2). For our study we characterized Ca2+ channels involved in ET-1-induced contractions and increases in the intracellular free Ca2+ concentration ([Ca2+]i) using these blockers. Our results show that the response to lower concentrations of ET-1 involves only one Ca2+ channel which is sensitive to SK&F 96365 and LOE 908 (NSCC-2). In contrast, the response to higher concentrations of ET-1 involves two types of Ca2+ channel in addition to NSCC-2: one is sensitive to SK&F 96365 but resistant to LOE 908 (SOCC), and the other is resistant to SK&F 96365 but sensitive to LOE 908 (NSCC-1). Furthermore, the percentage contribution of Ca2+ entry through NSCC-1, NSCC-2 and SOCC is calculated to be 10%, 50-60% and 30-40%, respectively.

Acetamides↗

PubMed2000

Pharmacological properties of calcium entry channels in A7r5 cells activated by endothelin-1.

Using whole-cell recordings of patch-clamp and monitoring of the intracellular free calcium (Ca2+) concentration ([Ca2+]i), we characterized Ca2+ entry channels in A7r5 cells activated by endothelin-1 (ET-1). ET-1 activates three types of voltage-independent Ca2+ entry channels: two types of Ca2+-permeable nonselective cation channels (designated NSCC-1 and NSCC-2) and store-operated Ca2+ channel (SOCC). Furthermore, it was found that these channels can be discriminated pharmacologically using Ca2+ channel blockers such as 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl)-1-H-imidazoe l hydrochloride (SK&F 96365) and (RS)-(3,4-dihydro-6,7-dimethoxyisoquinoline-1-gamma l)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxyphenyl)ethoxyl]acetamide (LOE 908). NSCC-1 is resistant to SK&F 96365 but sensitive to LOE 908, whereas NSCC-2 is sensitive to both drugs: SOCC is sensitive to SK&F 96365 but resistant to LOE 908. Using these channel blockers, we analyzed the Ca2+ entry channels involved in the ET-1-induced increase in [Ca2+]i of the cells. The increase induced by lower concentrations of ET-1 (< or = 0.1 nM) was unaffected by SK&F 96365 but it was abolished by LOE 908. In contrast, the increase caused by higher concentrations of ET-1 (> or = 1 nM) was suppressed by SK&F 96365 or LOE 908 to about 35% of controls, and abolished by combined treatment with SK&F 96365 and LOE 908. These results show that the increase in [Ca2+]i resulting from lower concentrations of ET-1 (< or = 0.1 nM) involves Ca2+ entry through only NSCC-1, whereas that resulting from higher concentrations of ET-1 involves Ca2+ entry through NSCC-1, NSCC-2 and SOCC, contributing 35%, 30% and 30%, respectively, to total Ca2+ entry.

Acetamides↗