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1.
The ability of vasopressin to elevate cytosolic Ca2+ in small cell lung cancer (SCLC) cells was investigated. Ten nanomolar vasopressin elevated the cytosolic Ca2+ in 6 of 8 SCLC cell lines that were loaded with Fura-2 AM. Using SCLC cell line NCI-H345, the effect of vasopressin was dose dependent, being maximal at 100 nM, where the cytosolic Ca2+ was elevated from 150 to 210 nM. Because addition of 1 mM EGTA had no effect on the vasopressin response, vasopressin released Ca2+ from intracellular pools. Also, oxytocin weakly elevated the cytosolic Ca2+. The response to vasopressin was strongly blocked by [(β-mercapto-β,β-cyclopentamethylene propionic acid)1,O-MeTyr2,Arg8]vasopressin and weakly blocked by [(β-mercapto-β,β-cyclopentamethylene propionic acid)1,O-MeTyr2,Orn8]vasotocin. These data suggest that V1 vasopressin receptors are present on SCLC cells. 相似文献
2.
Gerold Bepler Uwe Zeymer Samira Mahmoud Gary Fiskum Edmund Palaszynski Martin Rotsch James Willey Aurelia Koros Frank Cuttitta Terry W. Moody 《Peptides》1988,9(6):1367-1372
Human small cell lung cancer (SCLC) produces and secretes BN/GRP (bombesin/gastrin releasing peptide). Because BN stimulates the growth of SCLC cells and these cells have receptors for BN-like peptides, it is important to define agents which disrupt this self-promoting autocrine growth cycle. Here, substance P analogues were evaluated as BN receptor antagonists using SCLC cell lines. (D-Arg1, D-Pro2, D-Trp7,9, Leu11) substance P [(APTTL)SP] was one of the more potent analogues tested in inhibiting BN-like peptide receptor binding with an IC50 value of 1 μM. Micromolar concentrations of (APTTL)SP antagonized BN receptor mediated elevation of cytosolic Ca2+ levels and decreased the colony formation in soft agarose. These data suggest that SP analogues function as SCLC BN receptor antagonists and may be useful in disrupting the autocrine growth function of BN-like peptides. 相似文献
3.
Neurotensin (NT) has been postulated to act as a modulatory agent in the central nervous system. Besides its presence in mammalian brain, NT is produced by small cell carcinoma of the lung (SCLC) and cell lines derived from these tumors. Receptors have also been characterized in some SCLC cell lines leading to the suggestion that NT could regulate the growth of SCLC in an autocrine fashion similar to bombesin/GRP. Previously, we had reported that a 10 nM dose of NT and NT(8-13), but not NT(1-8), elevated cytosolic Ca2+, indicating that SCLC NT receptors may use Ca2+ as a second messenger. Using intact SCLC cells we report that time-course incubations with NT lead to the formation of the amino-terminal fragment NT(1-8) and small amounts of the C-terminal fragment NT(9-13). These fragments are formed by metalloendopeptidase 3.4.24.15 cleaving enzyme at the Arg8-Arg9 bond of NT. Significant levels of soluble 3.4.24.15 (10-17 nmoles/mg Pr-/min) are present in SCLC cell lines. Using the in vitro clonogenic assay we tested the effect of 0.5, 5.0 and 10.0 nM doses of NT, NT(1-8) and NT(8-13) on SCLC clonal growth. NT and the C-terminal fragment NT(8-13) stimulated colony formation whereas the N-terminal fragment did not. In summary, NT may function as a regulatory peptide in SCLC through the formation of peptide fragments. 相似文献
4.
We examined the profile of two bombesin (BN) antagonists, (CH3)2CHCO-His-Trp-Ala-Val-
-Ala-His-Leu-NHCH3] (ICI 216140) and [
-Phe6,des-Met14]BN(6–14)ethylamide (DPDM-BN EA), against neuromedin B-induced Ca2+ mobilization in the small cell lung cancer (SCLC) line NCI-H345. Neuromedin B (NMB), a BN-like peptide sharing sequence homology with ranatensin, elicited a concentration-dependent Ca2+ release (in part) from intracellular stores. Sequential addition of NMB attenuated Ca2+ mobilization. Desensitization occurred between BN and NMB; depletion of intracellular Ca2+ is a likely mechanism because thapsigargin stimulated Ca2+ release after a maximally desensitizing dose of NMB. ICI 216140 and DPDM-BN EA competitively inhibited BN-induced Ca2+ transients. In contrast, these compounds antagonized NMB-stimulated Ca2+ transients in a noncompetitive manner. The pharmacological profiles obtained support receptor heterogeneity for BN-like peptides on this SCLC line, underscoring the need for thorough examination of dose-response relationships when investigating effects of BN analogues on intact cells. 相似文献
5.
Intravenous administration of ovokinin(2–7), a cleavage peptide derived from ovalbumin, dose-dependently (0.1–5 mg/kg) lowered the mean arterial pressure (MAP) that was not accompanied by a significant change in the heart rate (HR) of urethane-anesthetized rats. The hypotensive effects of ovokinin(2–7) were five orders of magnitude lower compared to that of bradykinin and were largely prevented by pretreatment with the bradykinin B2 receptor antagonist HOE140 (81.6±18.4%) and moderately affected by the B1 receptor antagonist [des-Arg10]-HOE140 (26.3±15.5%). Intracellular Ca2+ levels, as measured by Fur 2-AM, were significantly elevated in cultured aorta smooth muscle cells by ovokinin(2–7). The increases were abolished by HOE140 and unaffected by [des-Arg10]-HOE140. The elevation of intracellular Ca2+ by ovokinin(2–7) was dependent on Ca2+ entry from extracellular space as it was reduced in a Ca2+-free solution. Pretreatment of the cells with the phospholipase C inhibitor U73122 (2 μM) eliminated the Ca2+ increase by the peptide. PA phosphohydrolase and phospholipase A2 inhibitors significantly reduced the responses as well. Our results show that ovokinin(2–7) modulates cardiovascular activity by interacting with B2 bradykinin receptors. 相似文献
6.
Bang-Ping Jiann Yih-Chau Lu Hong-Tai Chang Jong-Khing Huang Chung-Ren Jan 《Life sciences》2002,70(26):269-3178
The effect of clomiphene, an ovulation-inducing agent, on cytosolic free Ca2+ levels ([Ca2+]i) in populations of PC3 human prostate cancer cells was explored by using fura-2 as a Ca2+ indicator. Clomiphene at concentrations between 10-50 μM increased [Ca2+]i in a concentration-dependent manner. The [Ca2+]i signal was biphasic with an initial rise and a slow decay. Ca2+ removal inhibited the Ca2+ signal by 41%. Adding 3 mM Ca2+ increased [Ca2+]i in cells pretreated with clomiphene in Ca2+-free medium, confirming that clomiphene induced Ca2+ entry. In Ca2+-free medium, pretreatment with 50 μM brefeldin A (to permeabilize the Golgi complex), 1 μM thapsigargin (to inhibit the endoplasmic reticulum Ca2+ pump), and 2 μM carbonylcyanide m-chlorophenylhydrazone (to uncouple mitochondria) inhibited 25% of 50 μM clomiphene-induced store Ca2+ release. Conversely, pretreatment with 50 μM clomiphene in Ca2+-free medium abolished the [Ca2+]i increase induced by brefeldin A, thapsigargin or carbonylcyanide m-chlorophenylhydrazone. The 50 μM clomiphene-induced Ca2+release was unaltered by inhibiting phospholipase C with 2 μM 1-(6-((17β-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). Trypan blue exclusion assay suggested that incubation with clomiphene (50 μM) for 2-15 min induced time-dependent decrease in cell viability by 10-50%. Collectively, the results suggest that clomiphene induced [Ca2+]i increases in PC3 cells by releasing store Ca2+ from multiple stores in an phospholipase C-independent manner, and by activating Ca2+ influx; and clomiphene was of mild cytotoxicity. 相似文献
7.
Tumour-promoting phorbol esters (phorbol-12-myristate-13-acetate, PMA; phorbol-12,13-dibutyrate, PDBu) but not 4β-phorbol, activate protein kinase C. Using human platelets pre-labelled with quin2 or 32PO4 we examined the effects of these compounds on human platelet cytosolic free Ca2+ ([Ca2+]j) and on [32]phosphatidic acid ([32P]PtdOH). PMA and PDBu, but not 4β-phorbol inhibited thrombin-, PAF- and vasopressin-induced elevation of [Ca2+], and [2+P]PtdOH formation. It is suggested that protein kinase C may act to terminate the transduction processes that link receptor occupancy to cellular activation. 相似文献
8.
Distribution, functional role, and signaling mechanism of adrenomedullin receptors in the rat adrenal gland 总被引:2,自引:0,他引:2
Mazzocchi G Albertin G Andreis PG Neri G Malendowicz LK Champion HC Bahçelioglu M Kadowitz PJ Nussdorfer GG 《Peptides》1999,20(12):1383-1487
Adrenomedullin (ADM) is a hypotensive peptide, highly expressed in the mammalian adrenal medulla, which belongs to a peptide superfamily including calcitonin gene-related peptide (CGRP) and amylin. Quantitative autoradiography demonstrated the presence of abundant [125I]ADM binding sites in both zona glomerulosa (ZG) and adrenal medulla. ADM binding was selectively displaced by ADM(22–52), a putative ADM-receptor antagonist, and CGRP(8–37), a ligand that preferentially antagonizes the CGRP1-receptor subtype. ADM concentration-dependently inhibited K+-induced aldosterone secretion of dispersed rat ZG cells, without affecting basal hormone production. Both ADM(22–52) and CGRP(8–37) reversed the ADM effect in a concentration-dependent manner. ADM counteracted the aldosterone secretagogue action of the voltage-gated Ca2+-channel activator BAYK-8644, and blocked K+- and BAYK-8644-evoked rise in the intracellular Ca2+ concentration of dispersed ZG cells. ADM concentration-dependently raised basal catecholamine (epinephrine and norepinephrine) release by rat adrenomedullary fragments, and again the response was blocked by both ADM(22–52) and CGRP(8–37). ADM increased cyclic-AMP release by adrenal-medulla fragments, but not capsule-ZG preparations, and the catecholamine response to ADM was abolished by the PKA inhibitor H-89. Collectively, the present findings allow us to draw the following conclusions: (1) ADM modulates rat adrenal secretion, acting through ADM(22–52)-sensitive CGRP1 receptors, which are coupled with different signaling mechanisms in the cortex and medulla; (2) ADM selectively inhibits agonist-stimulated aldosterone secretion, through a mechanism probably involving the blockade of the Ca2+ channel-mediated Ca2+ influx; (3) ADM raises catecholamine secretion, through the activation of the adenylate cyclase/PKA signaling pathway. 相似文献
9.
Chao YY Jan CR Ko YC Chen JJ Jiann BP Lu YC Chen WC Su W Chen IS 《Life sciences》2002,70(26):4367-3121
The effect of five lignans isolated from Hernandia nymphaeifolia on estrogenic compounds (17β-estradiol, tamoxifen and clomiphene)-induced Ca2+ mobilization in human neutrophils was investigated. The five lignans were epi-yangambin, epi-magnolin, epi-aschantin, deoxypodophyllotoxin and yatein. In Ca2+–containing medium, the lignans (50–100 μM) inhibited 10 μM 17β-estradiol- and 5 μM tamoxifen-induced increases in intracellular free Ca2+ levels ([Ca2+]i) without changing 25 μM clomiphene-induced [Ca2+]i increase. 17β-estradiol and tamoxifen increased [Ca2+]i by causing Ca2+ influx and Ca2+ release because their responses were partly reduced by removing extracellular Ca2+. In contrast, clomiphene solely induced Ca2+ release. The effect of the lignans on these two Ca2+ movement pathways underlying 17β-estradiol- and tamoxifen-induced [Ca2+]i increases was explored. All the lignans (50–100 μM) inhibited 10 μM 17β-estradiol-and 5 μM tamoxifen-induced Ca2+ release, and 17β-estradiol-induced Ca2+ influx. However, only 100 μM epi-aschantin was able to reduce tamoxifen-induced Ca2+ influx while the other lignans had no effect. Collectively, this study shows that the lignans altered estrogenic compounds-induced Ca2+ signaling in human neutrophils in a multiple manner. 相似文献
10.
钙信号是细胞调节各项生命活动的重要机制。神经元通过胞外钙离子(calcium ion, Ca2+)内流、内质网Ca2+释放以及Ca2+释放介导的Ca2+内流等方式产生具有时空特异性的钙信号,用于调控多种生物学过程,例如动作电位的调节、神经递质的释放、轴突的生长以及突触可塑性等。神经元胞内Ca2+浓度因受到细胞精确调控而处于动态平衡之中。若钙信号失调导致平衡被打破,则会造成神经元功能异常甚至死亡。近年来多项研究表明,钙稳态失衡与神经退行性疾病,例如阿尔茨海默病等的产生和发展密切相关,由此发展出关于阿尔茨海默病的钙假说。该假说认为,神经元钙稳态调节机制的持续性改变是神经元功能失常、大脑产生慢性疾病的重要因素。阿尔茨海默病发生发展过程中,神经元胞浆钙水平异常增高,致使多种钙依赖性酶的活性异常,进而影响基因转录。虽然内质网钙稳态的变化目前仍存在一定的争议,但较为确定的是线粒体中存在着钙超载的现象,导致氧化磷酸化反应下调,活性氧的产量增加,进而引发细胞凋亡。本文主要介绍了神经元钙信号系统及其功能,简要梳理了阿尔茨海默病钙假说的相关研究,并对后续研究进行了展望。 相似文献
11.
Hisayuki Ohata Ken-ichi Tanaka Hiromi Aizawa Yoko Ao Takeru Iijima Kazutaka Momose 《Cellular signalling》1997,9(8):609-616
We investigated the effect of lysophosphatidic acid (LPA), a bioactive phospholipid, on the response in cytosolic free Ca2+ concentration ([Ca2+]i) to mechanical stress in cultured bovine lens epithelial cells. Spritzing of bath solution onto cells as mechanical stress caused marked increase in [Ca2+]i in the presence of LPA and this increase was concentration-dependent (1–10 μM), whereas neither addition of LPA alone nor the mechanical stress in the absence of LPA affected [Ca2+]i. The mechanical stress-induced increase in [Ca2+]i in the presence of LPA was inhibited by removing extracellular Ca2+ or by addition of Gd3+, a blocker of mechanosensitive cation channels, but not by nicardipine, thapsigargin, an inhibitor of endoplasmic reticulum-ATPase pump, or U73122, a phospholipase C inhibitor. These results show that LPA sensitises Ca2+ influx through cation-selective mechanosensitive channels, but does not sensitise Ca2+ release from intracellular stores, triggered by changes in mechanical stress. On the other hand, phosphatidic acid had less of a sensitising effect than LPA, and neither lysophosphatidylcholine nor chlorpromazine had any effect. Also Ca2+ mobilising agonists, ATP, histamine and carbachol, did not sensitise Ca2+ response to the mechanical stress. These results show that LPA sensitises mechanoreceptor-linked response in lens epithelial cells, suggesting that it plays a role in the development of cataracts due to increases in [Ca2+]i induced by mechanical stress. 相似文献
12.
Using a new fluorescence imaging technique, LAMP, we recently reported that Ca2+ influx through store operated Ca2+ channels (SOCs) strongly inhibits cell coupling in primary human fibroblasts (HF) expressing Cx43. To understand the mechanism of inhibition, we studied the involvement of cytosolic pH (pHi) and Ca2+([Ca2+]i) in the process by using fluorescence imaging and ion clamping techniques. During the capacitative Ca2+ influx, there was a modest decline of pHi measured by BCECF. Decreasing pHi below neutral using thioacetate had little effect by itself on cell coupling, and concomitant pHi drop with thioacetate and bulk [Ca2+i rise with ionomycin was much less effective in inhibiting cell coupling than Ca2+ influx. Moreover, clamping pHi with a weak acid and a weak base during Ca2+ influx largely suppressed bulk pHi drop, yet the inhibition of cell coupling was not affected. In contrast, buffering [Ca2+i with BAPTA, but not EGTA, efficiently prevented cell uncoupling by Ca2+ influx. We concluded that local Ca2+ elevation subjacent to the plasma membrane is the primary cause for closing Cx43 channels during capacitative Ca2+ influx. To assess how Ca2+ influx affects junctional coupling mediated by other types of connexins, we applied the LAMP assay to Hela cells expressing Cx26. Capacitative Ca2+ influx also caused a strong reduction of cell coupling, suggesting that the inhibitory effect by Ca2+ influx may be a more general phenomenon. 相似文献
13.
Thomas E. Fisher Charles W. Bourque 《Progress in biophysics and molecular biology》2001,77(3):2022-303
By mediating the Ca2+ influx that triggers exocytotic fusion, Ca2+ channels play a central role in a wide range of secretory processes. Ca2+ channels consist of a complex of protein subunits, including an 1 subunit that constitutes the voltage-dependent Ca2+-selective membrane pore, and a group of auxiliary subunits, including β, γ, and 2–δ subunits, which modulate channel properties such as inactivation and channel targeting. Subtypes of Ca2+ channels are constituted by different combinations of 1 subunits (of which 10 have been identified) and auxiliary subunits, particularly β (of which 4 have been identified). Activity-secretion coupling is determined not only by the biophysical properties of the channels involved, but also by the relationship between channels and the exocytotic apparatus, which may differ between fast and slow types of secretion. Colocalization of Ca2+ channels at sites of fast release may depend on biochemical interactions between channels and exocytotic proteins. The aim of this article is to review recent work on Ca2+ channel structure and function in exocytotic secretion. We discuss Ca2+ channel involvement in selected types of secretion, including central neurotransmission, endocrine and neuroendocrine secretion, and transmission at graded potential synapses. Several different Ca2+ channel subtypes are involved in these types of secretion, and their function is likely to involve a variety of relationships with the exocytotic apparatus. Elucidating the relationship between Ca2+ channel structure and function is central to our understanding of the fundamental process of exocytotic secretion. 相似文献
14.
Kreiling JA Balantac ZL Crawford AR Ren Y Toure J Zchut S Kochilas L Creton R 《Mechanisms of development》2008,125(5-6):396-410
Vertebrate embryos generate striking Ca2+ patterns, which are unique regulators of dynamic developmental events. In the present study, we used zebrafish embryos as a model system to examine the developmental roles of Ca2+ during gastrulation. We found that gastrula stage embryos maintain a distinct pattern of cytosolic Ca2+ along the dorsal–ventral axis, with higher Ca2+ concentrations in the ventral margin and lower Ca2+ concentrations in the dorsal margin and dorsal forerunner cells. Suppression of the endoplasmic reticulum Ca2+ pump with 0.5 μM thapsigargin elevates cytosolic Ca2+ in all embryonic regions and induces a randomization of laterality in the heart and brain. Affected hearts, visualized in living embryos by a subtractive imaging technique, displayed either a reversal or loss of left–right asymmetry. Brain defects include a left–right reversal of pitx2 expression in the dorsal diencephalon and a left–right reversal of the prominent habenular nucleus in the brain. Embryos are sensitive to inhibition of the endoplasmic reticulum Ca2+ pump during early and mid gastrulation and lose their sensitivity during late gastrulation and early segmentation. Suppression of the endoplasmic reticulum Ca2+ pump during gastrulation inhibits expression of no tail (ntl) and left–right dynein related (lrdr) in the dorsal forerunner cells and affects development of Kupffer’s vesicle, a ciliated organ that generates a counter-clockwise flow of fluid. Previous studies have shown that Ca2+ plays a role in Kupffer’s vesicle function, influencing ciliary motility and translating the vesicle’s counter-clockwise flow into asymmetric patterns of gene expression. The present results suggest that Ca2+ plays an additional role in the formation of Kupffer’s vesicle. 相似文献
15.
Jian Wang C. Bruce Verchere Christopher H. S. McIntosh John C. Brown 《Cell communication & adhesion》1994,1(4):343-353
The intracellular free Ca2+ ion concentration ([Ca2+]i) was measured using fura-2 microspec-trofluorimetry in individual rat pancreatic β-cells prepared by enzymatic digestion and fluorescence-activated cell sorting. The mean basal concentration of [Ca2+]i in β-cells in the presence of 4.4 mM glucose and 1.8 mM Ca2+ was 112±1.6 nM (n=207). The action of acetylcholine (ACh) was concentration-dependent, and raising the concentration resulted in [Ca2+]i spikes of increasing amplitude and duration in some, but not all of the β-cells. In addition, the β-cells demonstrated variable sensitivity to ACh. The increases in [Ca2+]i were rapid, transient and were blocked by atropine at 10-6M. A brief exposure to 50 mM K+ resulted in a transient increase in [Ca2+]i similar to that induced by ACh, but resistant to atropine. A high concentration of ACh (100μL 10-4M or 10-3M) induced [Ca2+]i oscillations in 11 out of 57 β-cells in the presence of 4.4 mM glucose. Using calcium channel blockers and Ca2+ free medium, the source of the increase in [Ca2+]i was deduced to be from extracellular spaces. Changing the temperature from 22 to 37°C did not affect the action of ACh on [Ca2+]i. These data strongly suggest that ACh exerted a direct action on [Ca2+]i in normal rat pancreatic β-cells and support a role for Ca2+ as a second messenger in the action of ACh. 相似文献
16.
David G. Witte Alex M. Nadzan Jean Martinez Marc Rodriguez Chun Wel Lin 《Peptides》1992,13(6):1227-1232
The interaction of the novel CCK analogs JMV-180, JMV-320, and JMV-332 with CCK-B/gastrin receptors on small cell lung cancer (SCLC) cells was investigated. JMV-180, JMV-320, and JMV-332 potently inhibited specific binding of 125I-CCK-8 to CCK-B/gastrin receptors expressed on the SCLC cell line NCI-H345 (H345) with IC50 values of 4.9, 1.8, and 7.0 nM, respectively. JMV-320 and JMV-332 stimulated intracellular calcium ([Ca2+]i) release in a dose-dependent manner in cells preloaded with indo-1. JMV-180 did not stimulate [Ca2+]i but inhibited the [Ca2+]i release elicited by 10 nM CCK-8 in a dose-dependent manner. These data indicate that JMV-320 and JMV-332 function as CCK-B/gastrin receptor agonists while JMV-180 functions as a CCK-B/gastrin receptor antagonist in H345 cells. 相似文献
17.
Tang SY Whiteman M Jenner A Peng ZF Halliwell B 《Free radical biology & medicine》2004,36(12):1588-1611
YCT is a semipurified extract from Cratoxylum cochinchinense that has antioxidant properties and contains mostly mangiferin. We show here that YCT is selectively toxic to certain cell types and investigate the mechanisms of this toxicity in Jurkat T cells. By flow cytometric analyses, we show that YCT causes intense oxidative stress and a rise in cytosolic Ca2+. This is followed by a rise in mitochondrial Ca2+, release of cytochrome c, collapse of Δψm, a fall in ATP levels, and eventually cell death. The mechanism(s) of intense oxidative stress may involve a plasma membrane redox system, as cell death is inhibited by potassium ferricyanide. Cell death has some features of apoptosis (propidium iodide staining, externalization of phosphatidylserine, limited caspase-3 and -9 activities), but there was no internucleosomal DNA fragmentation. 相似文献
18.
Naturally occurring neurotoxins, 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinolines (DHTIQs), thought to be the causative agents of Parkinsonism. DHTIQs including norsalsolinol have been found in the mammalian central nervous system. Norsalsolinol can be formed by a non-enzymatic Pictet–Spengler condensation reaction between dopamine and formaldehyde, and has been detected in the urine of Parkinsonian patients. However, the effects of DHTIQs on the secretion of dopamine, as well as other neurotransmitters, are not well understood. This study investigated the effects of norsalsolinol on dopamine secretion from nerve growth factor-differentiated PC12 cells. Norsalsolinol (1–100 μM) pretreatment suppressed both ATP (100 μM)- and K+ (50 mM)-induced dopamine secretion from PC12 cells in a concentration-dependent fashion, but did not affect basal dopamine secretion. In β-escin-permeabilized PC12 cells, norsalsolinol pretreatment suppressed Ca2+ (pCa=4–8)-induced dopamine secretion, but did not inhibit the secretagogue-induced change in intracellular Ca2+ concentration. These results suggest that norsalsolinol causes the inhibition of secretagogue-induced dopamine secretion from PC12 cells without altering intracellular Ca2+ concentration. Inhibition of dopamine secretion by norsalsolinol may also be involved in postural abnormality in Parkinson's disease. 相似文献
19.
Exposure of hepatoma lclc7 cells to 2,3-drniethoxy-1.4-naphthoquinone (DMNQ) resulted in a sustained elevation of cytosolic Ca2+. DNA single strand breaks and cell killing. DNA single strand break formation was prevented when cells were preloaded with either of the intracellular Ca2+ chelators. Quin 2 or BAPTA, to buffer the increase in cytosolic Ca2+ concentration induced by the quinone. DMNQ caused marked NAD+ depletion which was prevented when cells were preincubated with 3-aminobenzamide. an inhibitor of nuclear poly-(ADP-ribose)-synthetase activity. or with either of the two Ca2+ chelators. However. 3-aminobenzamide did not protect the hepatoma cells from loss of viability. Our results indicate that quinone-induced DNA damage. NAD+ depletion and cell killing are mediated by a sustained elevation of cytosolic Ca2+ 相似文献
20.
Electron microscopic and biochemical techniques were used to study the cellular localization of the ATP-dependent, IP3-sensitive, Ca2+ store in the glucose- and phosphatidylinositol(PI) agonist-sensitive hamster insulinoma cell line HIT-T15. Scanning electron microscopy revealed conspicuous shape changes of the microvilli following stimulation of these cells with bombesin or thapsigargin. These changes closely resemble those previously shown to accompany stimulation of hexose transport in adipocytes with insulin [J. Cell. Physiol. 142 (1990) 1-14]. Using a hydrodynamic shearing technique for the isolation of microvilli, two cell surface-derived vesicle fractions were prepared containing 80% of the total cellular Ca2+-storing activity. In contrast, subcellular fractionation using normal homogenization with a glass/teflon homogenizer yielded the well-known distribution of the Ca2+-storing activity which is then predominantly recovered within the microsomal fraction. The surface-derived vesicle fraction was clearly distinguished from the microsomal fraction by its high content of Na+/K+-ATPase and an immunoreactive fragment of the GluT-1 glucose transporter isoform which both are not detectable in the microsomal fraction isolated from homogenates from sheared cells. The Ca2+ uptake properties of the cell surface-derived vesicle fractions including the vanadate, A23187, and thapsigargin sensitivity were found to be identical with those described for the microsomal Ca2+ stores of various cell types. Inositol 1,4,5-trisphosphate (IP3) at 1 μM induced a maximal release of 35–40% of the stored Ca2+ from these vesicles. 相似文献