Thrombin and histamine stimulate the phosphorylation of elongation factor 2 in human umbilical vein endothelial cells

The effects of thrombin and histamine on protein phosphorylation in intact cultured human umbilical vein endothelial cells (HUVEC) prelabeled with 32PO4 were investigated. Incubation of HUVEC with either thrombin or histamine, agonists known to induce rapid transient increases in intracellular calcium levels in HUVEC, caused a rapid reversible increase in the phosphorylation of a protein with a Mr = 100,000 independent of the presence of extracellular calcium. Immunological and biochemical studies demonstrated that this Mr = 100,000 protein is elongation factor 2 (EF-2), a substrate previously shown to be phosphorylated by calcium/calmodulin-dependent protein kinase III (Nairn, A. C., and Palfrey, H. C. (1987) J. Biol. Chem. 262, 17299-17303). EF-2 is crucial for protein synthesis because it catalyzes the translocation of peptidyl-tRNA on the ribosome. Phosphoamino acid analysis of the EF-2 immunoprecipitated from HUVEC revealed that all of the thrombin-stimulated phosphorylation occurred on threonine. EF-2 was also phosphorylated when HUVEC were treated with the calcium ionophore, ionomycin. Phosphorylation of EF-2 was not increased by treatment with D-Phe-Pro-Arg-chloromethyl ketone thrombin, phorbol dibutyrate, forskolin, or 8-bromo-cGMP. The transient nature of the phosphorylation of EF-2 is consistent with it having a role in mediating some of the transient effects of thrombin and histamine on endothelial cell protein synthesis and functional capabilities.     

Involvement of c‐Jun N‐terminal kinase and extracellular signal‐regulated kinase 1/2 in EGF‐induced angiogenesis

Angiogenesis is a process during which endothelial cells divide and migrate to form new capillaries from the preexisting blood vessels. The present study was designed to investigate whether MAPKs (mitogen‐activated protein kinases) play crucial roles in regulating EGF (epidermal growth factor)‐induced endothelial cell angiogenesis. Our results showed that EGF stimulated HUVEC (human umbilical vein endothelial cells) proliferation in a concentration‐dependent manner, of which the maximum effective concentration of EGF was 10 ng/ml. Western blot analysis showed that EGF at 10 ng/ml significantly induced the phosphorylation of ERK1/2 (extracellular signal‐regulated kinase 1 and 2) and p38 kinase at 5 min, while it induced the phosphorylation of JNK/SAPK (c‐Jun N‐terminal kinase/stress‐activated protein kinase) at 15 min. Further results showed that a JNK/SAPK inhibitor, SP600125, and a specific siRNA JNK/SAPK could both significantly inhibit EGF‐induced tube formation in HUVEC cells, and an ERK1/2 inhibitor PD098059 could also block the tube formation in some content, while a p38 inhibitor SB203580 failed to do so. Furthermore, only SP600125 significantly inhibited EGF‐induced HUVEC cell proliferation under no cytotoxic concentration, so did JNK/SAPK siRNA. In conclusion, JNK/SAPK and ERK1/2 signals therefore play critical roles in EGF‐mediated HUVEC cell angiogenesis.     

Endothelial cell proliferation induced by HARP: implication of N or C terminal peptides

HARP (Heparin Affin Regulatory Peptide) is a 18-kDa secreted protein displaying high affinity for heparin. It has neurite outgrowth-promoting activity, while there are conflicting results regarding its mitogenic activity. In the present work, we studied the effect of human recombinant HARP expressed in bacterial cells as well as two peptides (HARP residues 1-21 and residues 121-139) on the proliferation of three endothelial cell types derived from human umbilical vein (HUVEC), rat adrenal medulla (RAME), and bovine brain capillaries (BBC) either added as a soluble form in the cell culture medium or coated onto the culture plate. HARP added in a soluble form in the culture medium had no effect on the proliferation of BBC, HUVEC, and RAME cells. However, when immobilized onto the cell culture plate, HARP had a concentration-dependent mitogenic effect on both BBC cells and HUVEC. The peptides presented as soluble factor induced a significant concentration-dependent mitogenic effect on BBC cells but only a small effect on HUVEC and RAME cells. When they were immobilized onto the cell culture plate, the mitogenic effect was much greater. The most responsive cells were BBC that expressed and secreted in the culture medium the higher amounts of HARP.     

TNF-alpha employs a protein-tyrosine phosphatase to inhibit activation of hepatocyte growth factor receptor and hepatocyte growth factor-induced endothelial cell proliferation

TNF-alpha impairs endothelial cell growth and angiogenesis. The anti-angiogenic effects of TNF-alpha have mainly been explained by its modulating vascular endothelial growth factor (VEGF)-specific angiogenic pathway. Hepatocyte growth factor (HGF) also promotes the growth of vascular endothelial cells and the development of new blood vessels through interaction with its specific receptor, c-met. However, it is little known whether TNF-alpha interacts with the HGF system or not. In this study, we examined the effect of TNF-alpha on HGF receptor function. In human umbilical venous endothelial cells (HUVEC), TNF-alpha acutely inhibited the phosphorylation and activation of c-met induced by HGF. The ability of TNF-alpha to inhibit HGF-induced c-met activity was impaired by sodium orthovanadate, suggesting that the inhibitory effect of TNF-alpha was mediated by a protein-tyrosine phosphatase. Treatment of HUVEC with TNF-alpha impairs the ability of HGF to activate MAPK and Akt, and this effect was blocked by SOV. HGF-induced c-met responses specifically associated with endothelial cell proliferation and mitogen-activated protein kinase activation were also inhibited by TNF-alpha, and these were reversed by sodium orthovanadate. HGF-induced SHP-1 (a cytoplasmic protein-tyrosine phosphatase) and pretreatment of HUVEC with TNF-alpha prior to HGF treatment resulted in substantial increase in the amount of SHP-1. These data suggest that TNF-alpha employs a protein-tyrosine phosphatase and may exert its anti-angiogenic function in part by modulating the HGF-specific angiogenic pathway in pathological settings.     

The respective 27 kDa and 28 kDa protein kinase C substrates in vascular endothelial and MCF-7 cells are most probably heat shock proteins

The phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulated the phosphorylation of two distinct 27 kDa and 28 kDa proteins, respectively, in bovine vascular endothelial cells and in MCF-7 human breast cancer cells. These protein phosphorylation events were correlated to striking opposite cell growth responses to TPA, i.e., stimulation of vascular endothelial cell proliferation and inhibition of MCF-7 cell growth. Exposure of both vascular endothelial and MCF-7 cells to heat shock induced synthesis of the respective 27 kDa and 28 kDa proteins among a set of common and distinct other proteins as well as an increase in the degree of phosphorylation of the two 27 kDa and 28 kDa proteins. These results suggest that the two protein kinase C substrates very likely belong to the family of low molecular mass stress proteins.     

Effect of phorbol esters on cytosolic protein kinase C content and activity in the human monoblastoid U937 cell

12-O-Tetradecanoylphorbol-13-acetate (TPA) stimulates the human monoblastoid U937 cell to differentiate into a mature monocyte/macrophage-like cell. Since TPA may produce cellular responses by activating protein kinase C, the effects of TPA on kinase activity in the U937 cell were investigated. Brief exposures (less than or equal to 60 min) to TPA dramatically diminished protein kinase C-dependent phosphorylation of histone and endogenous substrates. However, using a peptide substrate corresponding to residues 720-737 of protein kinase C-epsilon, Ca2(+)-, phospholipid-, and diacylglycerol-dependent kinase activity was reduced only modestly after exposure to TPA. This phospholipid-dependent kinase activity coeluted on DEAE chromatography with protein kinase C. Examination of cytosolic protein kinase C content by Western blot analysis demonstrated a moderate decline in kinase content after TPA treatment. The decline was due primarily to loss of an 80-kDa species with preservation of a 76-kDa protein. The immunoreactive 76-kDa protein observed after TPA treatment comigrated on DEAE chromatography with the kinase activity phosphorylating the protein kinase C-epsilon peptide and had an elution profile similar to protein kinase C derived from untreated cells. Using antisera recognizing the catalytic and regulatory domains of the kinase, no evidence for proteolytic degradation of protein kinase C was observed. Although incubation of extracts from vehicle and TPA-treated cells inhibited the activity of partially purified protein kinase C, the degree of inhibition was similar in the two extracts. These findings suggest that TPA markedly diminishes protein kinase C-dependent phosphorylation of histone and endogenous substrates in part by altering kinase substrate specificity. These observations provide evidence for a novel post-translational process that can modulate protein kinase C-dependent phosphorylation.     

Diarsenic and tetraarsenic oxide inhibit cell cycle progression and bFGF- and VEGF-induced proliferation of human endothelial cells

Arsenic trioxide (As2O3, diarsenic oxide) has recently been reported to induce apoptosis and inhibit the proliferation of various human cancer cells derived from solid tumors as well as hematopoietic malignancies. In this study, the in vitro effects of As2O3 and tetraasrsenic oxide (As4O6) on cell cycle regulation and basic fibroblast growth factor (bFGF)- or vascular endothelial growth factor (VEGF)-stimulated cell proliferation of human umbilical vein endothelial cells (HUVEC) were investigated. Significant dose-dependent inhibition of cell proliferation was observed when HUVEC were treated with either arsenical compound for 48 h, and flow cytometric analysis revealed that these two arsenical compounds induced cell cycle arrest at the G1 and G2/M phases--the increases in cell population at the G1 and G2/M phase were dominantly observed in As2O3- and As4O6-treated cells, respectively. In both arsenical compounds-treated cells, the protein levels of cyclin A and CDC25C were significantly reduced in a dose-dependent manner, concomitant to the reduced activities of CDK2- and CDC2-associated kinase. In G1-synchronized HUVEC, the arsenical compounds prevented the cell cycle progression from G1 to S phase, which was stimulated by bFGF or VEGF, through the inhibition of growth factor-dependent signaling. These results suggest that arsenical compounds inhibit the proliferation of HUVEC via G1 and G2/M phase arrest of the cell cycle. In addition, these inhibitory effects on bFGF- or VEGF-stimulated cell proliferation suggest antiangiogenic potential of these arsenical compounds.     

Thrombin and histamine rapidly stimulate the phosphorylation of the myristoylated alanine-rich C-kinase substrate in human umbilical vein endothelial cells: evidence for distinct patterns of protein kinase activation.

Human alpha-thrombin and histamine each stimulates protein phosphorylation in human umbilical vein endothelial cells (HUVEC). We have identified the most prominent of these phosphoproteins by immunoprecipitation as the human homolog of the widely distributed myristoylated alanine-rich C-kinase substrate (MARCKS). Stimulation by 0.1-10 U/ml of alpha-thrombin produces a time-dependent, sustained (plateau 3-5 min) level of MARCKS phosphorylation. MARCKS phosphorylation requires thrombin catalytic activity but not receptor binding and is also seen in response to stimulation by a peptide, TR (42-55), that duplicates a portion of the thrombin receptor tethered ligand created by thrombin proteolytic activity. One micromolar histamine, like alpha-thrombin, produces sustained phosphorylation of MARCKS (plateau 3-5 min). In contrast, 100 microM histamine results in rapid but transient MARCKS phosphorylation (peak 1-3 min). HUVEC treated with 100 microM histamine for 5 min can be restimulated by alpha-thrombin but not fresh histamine, suggesting that the histamine receptor was desensitized. MARCKS phosphorylation can also be induced by several exogenous protein kinase C (PKC) activators and both alpha-thrombin- and histamine-induced MARCKS phosphorylation are inhibited by the PKC antagonist staurosporine. However, while prolonged PMA pretreatment ablates histamine-induced MARCKS phosphorylation, the ability of thrombin to induce MARCKS phosphorylation is retained. These findings provide evidence for agonist-specific pathways of protein kinase activation in response to thrombin and histamine in HUVEC.     

Failure of 1-oleoyl-2-acetylglycerol to mimic the cell-differentiating action of 12-O-tetradecanoylphorbol 13-acetate in HL-60 cells

Treatment of human promyelocytic leukemia cells (HL-60 cells) with 12-O-tetradecanoylphorbol 13-acetate (TPA) results in terminal differentiation of the cells to macrophage-like cells. Treatment of the cells with TPA induced marked enhancement of the phosphorylation of 28- and 67-kDa proteins and a decrease in that of a 75-kDa protein. When the cells were treated with diacylglycerol, i.e. 50 micrograms/ml 1-oleoyl-2-acetylglycerol (OAG), similar changes in the phosphorylation of 28-, 67-, and 75-kDa proteins were likewise observed, indicating that OAG actually stimulates protein kinase C in intact HL-60 cells. OAG (1-100 micrograms/ml), which we used, activated partially purified mouse brain protein kinase C in a concentration-dependent manner. Treatment of HL-60 cells with 10 nM TPA for 48 h caused an increase by about 8-fold in cellular acid phosphatase activity. Although a significant increase in acid phosphatase activity was induced by OAG, the effect was scant compared to that of TPA (less than 7% that of TPA). After 48-h exposure to 10 nM TPA, about 95% of the HL-60 cells adhered to culture dishes. On the contrary, treatment of the cells either with OAG (2-100 micrograms/ml) or phospholipase C failed to induce HL-60 cell adhesion. Ca2+ ionophore A23187 failed to act synergistically with OAG. In addition, hourly or bi-hourly cumulative addition of OAG for 24 h also proved ineffective to induce HL-60 cell adhesion. Our present results do not imply that protein kinase C activation is nonessential for TPA-induced HL-60 cell differentiation, but do demonstrate that protein kinase C activation is not the sole event sufficient to induce HL-60 cell differentiation by means of this agent.     

Thrombin-induced vimentin phosphorylation in cultured human umbilical vein endothelial cells

Cultured human umbilical vein endothelial cells were stimulated with thrombin (1 unit/ml) for 15-30 s and then lysed with a solution of Triton X-100 containing [gamma-32P]adenosine triphosphate. Thrombin-stimulated human umbilical vein endothelial cells showed an enhanced incorporation of 32P into at least 12 different proteins as compared to control cells treated similarly. The observed enhanced phosphorylation required the active site of thrombin because diisopropylphosphoryl-thrombin had no effect on the level of phosphorylation. The molecular weight of one of the phosphoproteins was similar to that of the intermediate filament protein vimentin (55-60 kDa), a major protein in endothelial cells. This 59-kDa protein was Triton X-100-insoluble and reacted on a Western blot with antibody raised in guinea pig against Chinese hamster ovary cell vimentin. Addition of the anti-vimentin antibody to the thrombin-stimulated, phosphorylated lysate immuno-precipitated a single 32P-labeled protein (59 kDa). These results demonstrate that thrombin rapidly stimulates the phosphorylation of vimentin in cultured endothelial cells and links thrombin stimulation to the phosphorylation of a cytoskeletal protein.     

Utilization of distinct signaling pathways by receptors for vascular endothelial cell growth factor and other mitogens in the induction of endothelial cell proliferation

This study was initiated to identify signaling proteins used by the receptors for vascular endothelial cell growth factor KDR/Flk1, and Flt1. Two-hybrid cloning and immunoprecipitation from human umbilical vein endothelial cells (HUVEC) showed that KDR binds to and promotes the tyrosine phosphorylation of phospholipase Cgamma (PLCgamma). Neither placental growth factor, which activates Flt1, epidermal growth factor (EGF), or fibroblast growth factor (FGF) induced tyrosine phosphorylation of PLCgamma, indicating that KDR is uniquely important to PLCgamma activation in HUVEC. By signaling through KDR, VEGF promoted the tyrosine phosphorylation of focal adhesion kinase, induced activation of Akt, protein kinase Cepsilon (PKCepsilon), mitogen-activated protein kinase (MAPK), and promoted thymidine incorporation into DNA. VEGF activates PLCgamma, PKCepsilon, and phosphatidylinositol 3-kinase independently of one another. MEK, PLCgamma, and to a lesser extent PKC, are in the pathway through which KDR activates MAPK. PLCgamma or PKC inhibitors did not affect FGF- or EGF-mediated MAPK activation. MAPK/ERK kinase inhibition diminished VEGF-, FGF-, and EGF-promoted thymidine incorporation into DNA. However, blockade of PKC diminished thymidine incorporation into DNA induced by VEGF but not FGF or EGF. Signaling through KDR/Flk1 activates signaling pathways not utilized by other mitogens to induce proliferation of HUVEC.     

MAP kinases, phosphatidylinositol 3-kinase, and p70 S6 kinase mediate the mitogenic response of human endothelial cells to vascular endothelial growth factor

Although the significance of vascular endothelial growth factor (VEGF) and its receptors in angiogenesis is well established, the signal transduction cascades activated by VEGF and their involvement in mediating the mitogenic response of endothelial cells to VEGF are incompletely characterized. Here we demonstrate that VEGF activates mitogen-activated protein (MAP) kinases, including the extracellular signal-regulated protein kinase (ERK) and p38 MAP kinase, phosphatidylinositol 3-kinase (PI 3-kinase), and p70 S6 kinase in human umbilical vein endothelial cells (HUVEC). The activation of these enzymes was assayed by kinase phosphorylation and by kinase activity towards substrates. Studies with PI 3-kinase inhibitors revealed that activation of p70 S6 kinase was mediated by PI 3-kinase. Selective inhibition of ERK, PI 3-kinase, and p70 S6 kinase with the inhibitors PD098059, LY294002, and rapamycin, respectively, inhibited VEGF-stimulated HUVEC proliferation. In marked contrast, the p38 MAP kinase inhibitor SB203580 not only failed to inhibit but actually enhanced HUVEC proliferation; this effect was associated with the phosphorylation of Rb protein. Rb phosphorylation resulted from a decrease in the level of the cdk inhibitor p27KiP1. These results indicate that the activities of ERK, PI 3-kinase, and p70 S6 kinase are essential for VEGF-induced HUVEC proliferation. p38 MAP kinase suppresses endothelial cell proliferation by regulating cell-cycle progression.     

Desensitization of inositol phosphate production after agonist stimulation of endothelial cells is not mediated by protein kinase C

To investigate the possible role of protein kinase C activation in the desensitization of inositol phosphate production in endothelial cells we compared desensitization induced by agonists to that induced by the phorbol ester TPA. While histamine or thrombin induced desensitization of inositol phosphate production is homologous TPA induced desensitization is heterologous. The protein kinase C inhibitor H-7 reduced TPA desensitization but had no effect on the agonist induced desensitization. While downregulation of protein kinase C by long term (24 hr) treatment of the cells with TPA reduced the desensitization mediated by short term TPA-treatment it did not affect the agonist induced desensitization. These results suggest that desensitization of inositol phosphate production after agonist stimulation of endothelial cells is not mediated by protein kinase C.     

Erbin plays a critical role in human umbilical vein endothelial cell migration and tubular structure formation via the Smad1/5 pathway

Angiogenesis is an important process in atherosclerosis. ErbB2 was proved to have an important role in vascular development, but it is still unclear whether Erbin expresses in vessels as well as its location and function in the vessels. In the current study, we investigated the location and function of Erbin in human umbilical veins. The human umbilical veins were prepared, and immunofluorescent analysis was performed to determine the expression of Erbin. Human umbilical vein endothelial cells (HUVECs) were cultured and the lentivirus (LV) containing Erbin RNAi was also prepared. After transfection with the lentivirus, CCK-8 assay and Annexin V-PI assay were used for cell proliferation and apoptosis, respectively. Cell migration was studied using the scratch wound healing assay and the transwell assay. The capillary-like tube formation assay was performed to illustrate the effect of Erbin on HUVEC tube formation. Expression of signaling pathway molecules was assessed with Western blot. The immunofluorescent analysis suggested that Erbin expressed in human umbilical veins and the majority of the Erbin is strongly colocalized in endothelial cells. Although knockdown of Erbin did not affect HUVEC proliferation and apoptosis, it significantly suppressed HUVEC migration and tubular structure formation. Erbin knockdown showed no effect on the ERK1/2 and Smad2/3 signaling pathways but significantly promoted Smad1/5 phosphorylation and nuclear translocation. Ablation of the Smad1/5 pathway decreased the effects of Erbin on endothelial cells. Erbin is mainly localized in endothelial cells in human umbilical veins and plays a critical role in endothelial cell migration and tubular formation via the Smad1/5 pathway.     

Synthesis of protein C in human umbilical vein endothelial cells.

By monitoring the activation of protein C and the regulation of factor Xa-catalyzed thrombin formation by the activated protein C (APC) on the surface of human umbilical vein endothelial cells (HUVEC), we found that functional protein C was synthesized in cultured HUVEC and expressed thereon in the presence of vitamin K. Furthermore, without exogenously added protein S, time-dependent and saturable accumulation of APC (20 fmol APC/10(5) cells) on the surface of HUVEC was observed. During prothrombin activation by the complex of membrane-bound factor Xa and endogenous factor Va formed on the surface of HUVEC, APC was generated, and the rate of thrombin formation decreased. Treatment of HUVEC with an antibody that inhibits the APC-catalyzed inactivation of endogenous factor Va clearly quenched the activity of surface-associated APC. Immunostaining of HUVEC with a horseradish peroxidase (HRP)-conjugated antibody that solely recognizes human protein C confirmed the presence of protein C on the surface of HUVEC. Northern blot analysis revealed that an about 1.8 kb mRNA species derived from HUVEC was hybridized with 32P-labeled protein C cDNA, as in the case of those from HepG2, which are known to synthesize normal protein C. The increase in the amount of protein C mRNA in HUVEC in parallel with cell growth provided supporting evidence for the synthesis of protein C during the culture of HUVEC. These results indicate that blood coagulation is regulated by endogenously generated and activated protein C, together with or without protein S, through inactivation of factor Va on the surface of endothelial cells.     

Possible role of protein phosphorylation in the mitogenic effect of high density lipoproteins on cultured vascular endothelial cells

The implication of protein phosphorylation in the mitogenic action of high density lipoproteins (HDL) on bovine vascular endothelial cells was investigated by incubating endothelial cell cultures in the presence of 32P-labeled phosphoric acid. The incorporation of 32P into proteins was measured after fractionation by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and autoradiography of the gel. In endothelial cells seeded at low density and made quiescent by serum starvation, HDL markedly and consistently enhanced the degree of phosphorylation of a Mr 27,000 protein in a time- and dose-dependent manner. Using 500 micrograms/ml HDL, 32P labeling of the 27-kDa protein was already measurable after 10 min of incubation and reached a maximum at 20-30 min. Minimal effective dose of HDL during a 30-min incubation period was in the range of 5-10 micrograms/ml. While the apolipoprotein moiety of HDL was able to mimic the effect of total HDL, the lipid part of HDL was not. Furthermore, fibroblast growth factor appeared to potentiate the effect of HDL on 27-kDa protein phosphorylation, in agreement with the synergism observed between fibroblast growth factor and HDL on endothelial cell proliferation. Two activators of protein kinase C, 12-O-tetradecanoylphorbol 13-acetate and 1-oleoyl-2-acetylglycerol also induced the phosphorylation of the 27-kDa protein. These results suggest that the 27-kDa protein may be a physiological substrate for protein kinase C and that HDL could exert their mitogenic effect on endothelial cells through activation of protein kinase C and subsequent protein phosphorylation.     

Expression and secretion of gro/MGSA by stimulated human endothelial cells.

Melanoma growth stimulatory activity factor (MGSA) is a polypeptide which was initially isolated from Hs294 human melanoma cells. Its sequence is identical to the deduced amino acid sequence of the human gro cDNA, isolated from a human tumor cell line. MGSA stimulates the proliferation of malignant melanoma cells, but its function for normal cells has not been defined. Here we report that human umbilical vein endothelial cells are capable of synthesizing and secreting MGSA. The expression and secretion of MGSA are strongly induced by factors often involved in inflammation such as IL-1, TNF, LPS and thrombin. The induction of MGSA mRNA is dose and time dependent and is independent of new protein synthesis. This stimulation could be mimicked by TPA, suggesting that the action could be mediated through activation of protein kinase C. Furthermore, addition of MGSA to the endothelial cell cultures induces gro/MGSA gene expression, implying that an autocrine mechanism exists. Our data suggest that the protein encoded by gro/MGSA mRNA may play a role in inflammation and exert its effects on endothelial cells in an autocrine fashion.     

人脐静脉内皮细胞的生物学特性及细胞内信号转导机制

本实验对人脐静脉内皮细胞（ＨＵＶＥＣ）合成与释放篾这活性多肽（ＶＰｓ）及其作用机制进行了研究。结果表明：（１）无神经支配的人脐血管内皮细胞（ＶＥＣ）所含ＶＰｓ较有神经支配的肠系膜血管ＶＥＣ多;（２）这些ＶＰＳ是ＶＥＣ自身合成且能释放到胞外;（３）血管活性肠肽（ＶＩＰ）和Ｐ物质（ＳＰ）使ＨＵＶＥＣ膜上Ｃａ＾２＋通道开放概率明显增加,生长抑制（ＳＯＭ）使其明显降低,但它们均使胞浆内「Ｃａ＾２＋」和ＣＡ