生长抑素抑制胰岛素分泌作用的分子机制

为探讨生长抑素抑制胰岛素分泌的分子机制，我们以ＨＩＴ细胞为模型进行体外实验，系统全面地探讨了其对胰岛素分泌、钙离子跨膜电流、细胞内钙离子浓度、细胞内钾离子外流以及ＨＩＴ细胞腺苷酸环化酶和ｃＡＭＰ水平的影响。发现生长抑素能在不影响ＨＩＴ细胞腺苷酸环化作用以及细胞内外钾离子分布的情况下剂量依赖性地抑制细胞胰岛素的分泌，同时伴有钙离子跨膜流动和细胞内钙离子水平的升高。百日咳毒素可拮抗生长抑素的这种抑制作用。这些资料表明，抑制细胞外钙离子通过百日咳毒素敏感性的Ｇ－蛋白调节的电压依赖性钙离子通道进入胰岛素分泌细胞，是生长抑素抑制胰岛素分泌的重要分子机制之一。     

老年胃酸分泌与生长抑素的研究

目的探讨老年胃泌酸功能与生长抑素的调节机制．方法我室应用ＲＩＡ法对２０例老年人和１５例青年人胃液及９只Ｗｉｓｔａｒ老年鼠，２０只青年鼠胃粘膜组织、血浆生长抑素含量进行测定，以及对老年人和青年人进行胃酸分泌试验．结果老年人组比青年组胃液生长抑素呈高水平分泌，空腹胃液ＳＳ为（１３６５±４４３）ｎｇ／Ｌｖｓ（８５９±３４５）ｎｇ／Ｌ，Ｐ＜００１；刺激后ＳＳ为（１９６７±６６４）ｎｇ／Ｌｖｓ（１１４１±１０７３）ｎｇ／Ｌ，Ｐ＜００１．老年人比青年人胃酸分泌量明显减少，ＢＡＯ为（３５±２１）ｍｍｏｌ／ｈｖｓ（６９±４４）ｍｍｏｌ／ｈ，Ｐ＜００１；ＰＡＯ为（１３６±６４）ｍｍｏｌ／ｈｖｓ（２０８±１１２）ｍｍｏｌ／ｈ，Ｐ＜００５．不同年龄Ｗｉｓｔａｒ大鼠胃粘膜组织生长抑素具有不同的生理浓度，在老龄鼠比青年鼠ＳＳ也呈高水平分布，为（４５２５±１８４２）ｎｇ／ｇ蛋白ｖｓ（１５０９±９３８）ｎｇ／ｇ蛋白，Ｐ＜００１．结论老年胃泌酸功能改变与生长抑素调节作用存在重要关系．     

胃酸分泌胃壁细胞信号转导机制研究进展

随着细胞生物学、分子生物学和各种显微研究技术的不断完善，对胃壁细胞泌酸机制的了解也有了长足的进步，文章对胃酸分泌胃壁细胞的细胞信号转导机制研究进展作一综述。     

生长抑素抑制肝癌增殖的研究进展

生长抑素（ｓｏｍａｔｏｓｔａｔｉｎ,ＳＳＴ）对肿瘤细胞的增殖抑制尤其受到关注。研究ＳＳＴ对肝癌细胞的增殖抑制作用,将对肝癌的临床治疗具有重要意义。 一、ＳＳＴ及其受体 １．ＳＳＴ及其结构特性：ＳＳＴ是一种由神经内分泌细胞、炎性细胞、免疫细胞所产生,针对离子、营养素、神经肽、神经递质、甲状腺和类固醇激素、生长因子、细胞因子起作用的调节多肽,其分布主要在中枢和周围神经系统,对多种生物学活动具有广泛的抑制作用［１］。天然ＳＳＴ主要指１４肽的ＳＳＴ－１４和２８肽的ＳＳＴ－２８,其中ＳＳＴ－１４是最主要的生…     

雷贝拉唑抑制大鼠胃壁细胞泌酸功能的机制研究

目的 探讨质子泵抑制剂雷贝拉唑对大鼠胃壁细胞泌酸功能的抑制作用.方法 将72只SD大鼠分成对照组(0.9%氯化钠溶液)、雷贝拉唑低剂量组(10 mg/kg)和雷贝拉唑高剂量组(20 mg/kg),每组24只.分别在1、2、4、6、12和24 h每组各处理4只大鼠.用氢氧化钠滴定法测定大鼠胃内pH值,比色法测定胃壁细胞内H+-K+-ATP酶活性,电镜下观察胃壁细胞超微结构的改变.结果 与对照组(1.97±0.30)相比,雷贝拉唑低剂量组(3.37±0.97)和高剂量组(5.96±0.26)在给药后1 h内胃液pH值显著升高(P<0.01),壁细胞H+-K+-ATP酶活性明显抑制(3.28±0.41比1.47±0.27和0.92±0.07,P<0.05).而且在给药12 h的差异仍有统计学意义(P<0.01).电镜下胃壁细胞超微形态改变与胃液pH值和壁细胞H+-K+-ATP酶活性变化相符.雷贝拉唑低剂量组与高剂量组在抑酸作用和起效时间方面差异有统计学意义(P<0.01).结论 壁细胞超微结构的变化和H+-K+-ATP酶活性能准确反映壁细胞的泌酸情况,雷贝拉唑能迅速强效抑制大鼠壁细胞的泌酸功能,且与剂量有关.     

人大肠癌生长抑素受体的初步研究

大肠癌是常见的消化道恶性肿瘤。许多研究表明，生长抑素（ＳＳ）对大肠癌细胞有明显的抑制作用［１］，但部分研究却未取得一致结果［２］。其原因是多方面的，其中癌组织是否表达生长抑素受体（ＳＳＲ）以及受体的特性是重要原因。因此，我们用受体放射分析法对人大肠癌...     

肝癌生长抑素受体mRNA表达的研究

生长抑素（SST）是一种广泛存在于人体内分泌系统中环状的多肽类激素，近来SST及其类似物对肝癌诊断及治疗方面的作用正日益受到关注，其多种生物活性的发挥是通过靶细胞膜上的特异性受体介导的。本实验应用逆转录聚合酶链反应（RTPCR）检测原发性及转移性肝癌癌组织、癌旁组织、非癌肝组织、人肝癌细胞株HepG2及人肝细胞QSG-7701中生长抑素受体（SSTR）五种亚型mRNA的表达情况。     

生长抑素受体SSTR 3基因对胃癌细胞生长的影响

目的克隆生长抑素受体SSTR3基因,构建其真核表达载体,外进行转染研究,探时SSTR3基因在胃癌细胞中的作用。方法从永生化的胃上皮细胞系GES中提取总RNA,经RT－PCR扩增出SSTR3基因．并构建真核表达载体pcDNA 3．1（＋）－SSTR3,转染胃癌细胞系MKN 45,以MTT法和流式细胞仪观察转染SSTR基因前后使用奥曲肽对胃癌细胞增殖和凋亡的影响。结果克隆的SSTR 3基因测序正确;构建的真核表达载体pcDNA3．1（＋）SSTR3能高表达SSTR3蛋白;转染SSTR3基因的胃癌细胞系MKN 45加用奥曲肽后,出现明显的增殖抑制和凋亡发生。结论SSSTR3基因介导了生长抑素类似物引起的胃癌细胞的增殖抑制和凋亡发生。通过基因转移使原来不表达SSTR3基因的胃癌细胞再表达,为生长抑素和SSTR3基因治疗胃癌提供了又有效途径。     

胰腺癌中生长抑素及其受体的研究现状

胰腺癌早期诊断困难,对化疗、放疗均不敏感。至今尚无理想的治疗措施。近年研究表明,生长抑素具有抗细胞增殖作用,并发现胰腺癌中有许多生长抑素受体亚型表达。生长抑素类似物(somatostatin analogue,SSA)可以抑制胰腺、胃肠激素分泌,阻碍肿瘤细胞生长,并已应用于临床治疗某些肿瘤,如:胰腺癌及其它多种恶性肿瘤,取得了一定的疗效。本文综述生长抑素和受体及其类似物在胰腺癌中的研究进展。     

幽门螺杆菌及其培养上清液粗提蛋白对兔离体胃壁细胞酸分泌的影响

目的 通过研究幽门螺杆菌(Hp)及其培养上清液粗提蛋白(BCF-P)对兔离体胃壁细胞酸分泌的影响,探讨Hp感染引起宿主胃酸分泌状态改变的可能机制.方法 兔胃体黏膜经Ⅰ型胶原酶消化、离心淘洗后获得新鲜分离的壁细胞,并进行短期培养.提取Hp培养上清液粗提蛋白(BCF-P)并进行真空干燥浓缩,HeLa细胞以中性红摄取试验鉴定其细胞空泡活性.兔离体壁细胞与Hp及BCF-P(100μg/ml)分别共孵育2、16 h和1、12 h,应用14C-氨基比林(14C-AP)摄取法测定Hp和BCF-P对组胺(1.0×10-4 mol/L)刺激的壁细胞酸分泌的影响;同时应用RT-PCR方法分析Hp和BCF-P对壁细胞H+-K+ ATP酶α亚基mRNA表达的影响.结果 (1)BCF-P中含有细胞空泡毒素(VacA),对HeLa细胞表现出细胞空泡活性.(2)与Hp共孵育2 h和16 h均能抑制组胺刺激的壁细胞酸分泌(P<0.05),抑制作用随孵育时间延长而增强,2 h抑制率为81%,16 h为94%;BCF-P作用1 h和12 h,均能抑制壁细胞酸分泌(P<0.05),抑制作用也随孵育时间延长而增强,1 h抑制率为24%,12 h为58%.(3)尽管与Hp孵育2 h能上调壁细胞H+-K+ATP酶α亚基mRNA表达(P<0.05),但孵育16 h则表现为下调其表达(P<0.05);BCF-P作用1 h和12 h,均抑制H+-K+ATP酶α亚基mRNA的表达(P<0.05).结论 Hp及其分泌的VacA可能通过下调壁细胞H+-K+ ATP酶表达水平来抑制组胺刺激的壁细胞酸分泌.     

兰索拉唑对离体壁细胞酸分泌的影响

目的应用兔离体壁细胞为模型,研究兰索拉唑体外抑酸效果.方法应用细胞淘洗与连续密度梯度离心相结合的方法分离兔胃黏膜壁细胞,以14C氨基比林摄取为酸分泌指标,观察西咪替丁及兰索拉唑对离体壁细胞组胺诱导的酸分泌的影响.结果壁细胞纯度达80%以上进行实验,兰索拉唑能明显抑制离体壁细胞组胺诱导的酸分泌,对组胺刺激酸分泌的50%抑制量(IC50)为9.59×10-8mol/L,明显高于H2受体拮抗剂(3.70×10-5mol/L).结论兰索拉唑对兔离体壁细胞组胺诱导的酸分泌具明显的抑制作用,效果优于西咪替丁;本研究为国内开展新的抑酸剂基础与临床研究提供了新方法.     

Effect of misoprostol on histamine-stimulated acid secretion and cyclic AMP formation in isolated canine parietal cells

Isolated canine parietal cells were used to study the ability of misoprostol to inhibit acid secretion in the presence of a number of acid secretagogues. Misoprostol inhibited histamine-stimulated acid secretion in a dose-dependent and noncompetitive manner. A concentration of 2–3×10^–9 M misoprostol inhibited maximal histamine-stimulated acid secretion by one half. Misoprostol had little to no effect on acid secretion stimulated by carbachol and dibutyryl cAMP, had no effect on the acid secretion directly stimulated by pentagastrin, and only modestly inhibited acid secretion stimulated by forskolin. Misoprostol noncompetitively inhibited cAMP formation in response to histamine, with an IC₅₀ value similar to that for the inhibition of histamine-stimulated acid secretion. These results indicate that: (1) misoprostol specifically inhibits histamine-stimulated acid secretion in parietal cells, and (2) the antisecretory action of misoprostol is closely related to the reduction of histamine-stimulated cAMP formation with the site of major action most likely in the coupling process between histamine H₂ receptor sites and histamine-sensitive adenylate cyclase.     

Effect of lansoprazole on histamine‐induced acid secretion in isolated rabbit parietal cells

OBJECTIVE: Lansoprazole (Takepron; Takeda) is extensively used in the treatment of acid‐related diseases. There are no prior studies of the effects of antisecretion drugs on parietal cells, but we recently developed a rabbit parietal cell model. This allowed us to compare the antisecretory effects of lansoprazole and cimetidine in vitro in the present study. METHODS: Parietal cells were isolated using cell elutriation and continuous density gradient centrifugation. The effect of cimetidine and lansoprazole on histamine‐induced acid secretion in rabbit parietal cells was investigated by measuring the accumulation of ¹⁴C‐aminopurine. RESULTS: The purity and viability of isolated parietal cells was >80 and 95%, respectively. Lansoprazole and cimetidine both significantly inhibited histamine‐stimulated acid secretion (10^?4 mol/L), but the 50% inhibition concentration (IC₅₀) of the two treatments was quite different. The IC₅₀ of cimetidine was 3.70 × 10^?5 mol/L, and that of lansoprazole was 9.59 × 10^?8 mol/L. CONCLUSIONS: Lansoprazole is much more effective than cimetidine in the in vitro inhibition of histamine‐stimulated acid secretion in rabbit parietal cells. This study developed a model for the study of acid inhibition drugs.     

Nesfatin-1对离体胃黏膜细胞胃酸分泌的影响

目的:研究nesfatin-1对离体培养的大鼠胃黏膜酸分泌的影响,探讨nesfatin-1对H+/K+-ATP酶mRNA及蛋白表达的影响.方法:酶解法分离大鼠胃黏膜细胞,细胞免疫荧光检测法鉴定细胞.用不同浓度的nesfatin-1(10-4-10-1μmol/L)对胃黏膜细胞进行处理0、1、2、3、4h,设立空白对照组,以14C-氨基比林摄取为酸分泌指标,检测nesfatin-1对大鼠离体的胃黏膜细胞酸分泌的影响.用RT-PCR法及Western印迹法检测nesfatin-1对胃黏膜细胞H+/K+-ATP酶alpha(α)亚基和beta(β)亚基mRNA及蛋白表达的影响.结果:Nesfatin-1在10-1μmol/L浓度下,在1、2h能够抑制离体培养的大鼠胃黏膜细胞的酸分泌.Nesfatin-1(10-1μmol/L)在1、2、3h均能够抑制H+/K+-ATP酶α亚基mRNA表达水平;在1、2h能够抑制H+/K+-ATP酶β亚基mRNA表达水平,分别与对照组相比,差异有统计学意义(均P<0.01).Nesfatin-1(10-4-10-1μmol/L)作用胃黏膜细胞2h时,呈剂量依赖性抑制α亚基和β亚基mRNA表达水平,分别与对照组相比,差异有统计学意义(均P<0.01).Nesfatin-1(10-1μmol/L)在1、2、3h能够抑制α亚基蛋白表达水平;在2、3h能够抑制β亚基蛋白表达水平,分别与对照组相比,差异有统计学意义(均P<0.01).Nesfatin-1(10-3-10-1μmol/L)作用胃黏膜细胞2h时,呈剂量依赖性抑制α亚基和β亚基蛋白表达水平,与对照组相比,差异有统计学意义(均P<0.01).结论:Nesfatin-1能抑制离体培养的大鼠胃黏膜细胞的酸分泌,有可能是通过下调H+/K+-ATP酶α亚基和β亚基的mRNA及蛋白表达的水平影响酸分泌.     

Role of potassium in acid secretion

Potassium (K~+) ions are critical for the activation and catalytic cycle of the gastric H~+,K~+-ATPase, resulting in the secretion of hydrochloric acid into the parietal cell canaliculus. As both symptom, severity and esophageal mucosal damage in gastro-esophageal reflux disease (GERD) are related to the degree of acid exposure, K~+ is a logical target for approaches to inhibit acid production. The probable K~+ binding site on the gastric H~+,K~+-ATPase has recently been described and studies are elucidating how K~+ activates the enzyme. K~+ channels in the apical membrane of the parietal cell are implicated in the recycling of K~+ and, to date, three potential K~+ channels (KCNQ1, Kir2.1 and Kir4.1) have been identified. The channels represent theoretical sites for agents to control acid secretion but it will be difficult to develop selective blockers. An alternative strategy is to prevent K~+ from activating gastric H~+,K~+-ATPase; the potassiumcompetitive acid blocker (P-CAB) class inhibits acid secretion by binding at or near the K~+ binding site. Ongoing research is further defining the role of K~+ in the functioning of the gastric H~+,K~+-ATPase, as well as determining the clinical utility of agents directed toward this important cation.     

Histamine 3 receptor activation mediates inhibition of acid secretion during Helicobacter-induced gastritis

AIM: To test the hypothesis that histamine 3 receptor (H3R) activation during Helicobacter infection inhibits gastric acid secretion in vivo and in vitro.METHODS: Helicobacter felis (H. felis) infected and uninfected C57Bl/6 mice were infused with either PBS or the H3 receptor antagonist thioperamide (THIO) for 12 wk. After treatment, mice were analyzed for morphological changes and gastric acid content. Total RNA was prepared from the stomachs of each group and analyzed for changes in somatostatin and gastrin mRNA abundance by real time-polymerase chain reaction (RT-PCR). Location of H3 receptors in the stomach was analyzed by co-localization using antibodies specific for the H3 receptor and parietal cell marker H⁺, K⁺-ATPase β subunit.RESULTS: Inflammation and parietal cell atrophy was observed after 12 wk of H. felis infection. Interestingly, treatment with the H3R antagonist thioperamide (THIO) prior to and during infection prevented H. felis-induced inflammation and atrophy. Compared to the uninfected controls, infected mice also had significantly decreased gastric acid. After eradication of H. felis with THIO treatment, gastric acidity was restored. Compared to the control mice, somatostatin mRNA abundance was decreased while gastrin gene expression was elevated during infection. Despite elevated gastric acid levels, after eradication of H. felis with THIO, somatostatin mRNA was elevated whereas gastrin mRNA was suppressed. Immunofluorescence revealed the presence of H3 receptors on the parietal cells, somatostatin-secreting D-cells as well as the inflammatory cells.CONCLUSION: This study shows that during H. felis infection, gastric acidity is suppressed as a consequence of an inhibitory effect on the parietal cell by H3R activation. The stimulation of gastric mucosal H3Rs increases gastrin expression and release by inhibiting release of somatostatin.