血管活性肠肽对人胰腺癌细胞生长自分泌调节作用及其机制的研究

采用＾３Ｈ－胸腺嘧啶掺入研究了血管活性肠肽（ＶＩＰ）对我院所建一株人胰腺癌细胞生长的影响，并对该细胞株进行ＶＩＰ受体、受休珀细胞内介质ｃＡＭＰ和多胺产生的研究。发现ＶＩＰ在１０＾－６Ｍ和１０＾－７Ｍ对具有ＶＩＰ受体的人胰腺癌细胞有明显促生长作用，且成浓度依赖关系，这种作用可被其受体拮抗剂（４－Ｃｌ－ＤＰｈｅ＾６，Ｌｅｕ＾１７）ＶＩＰ所阻断；ＶＩＰ能显著促进本株人胰腺癌细胞内ｃＡＭＰ及多胺的产生，表     

血管活性肠肽受体在大鼠肝脏贮脂细胞的表达及其在肝纤维化中的意义

在特异引物引导下，用反转录ＰＣＲ方法扩增出预期长度的大鼠血管活性肠肽受体（ｖａｓｏａｃｔｉｖｅｉｎｔｅｓｔｉｎａｌｐｅｐｔｉｄｅｒｅｃｅｐｔｏｒＶＩＰ－Ｒ）的ｃＤＮＡ片断（７５０ｂｐ），随后该ｃＤＮＡ片段与３２Ｐ－标记的ＶＩＰ－Ｒ探针进行Ｓｏｕｔｈｅｒｎ杂交，结果证实大鼠肝脏贮脂细胞有ＶＩＰ－Ｒ的ｍＲＮＡ表达。放射受体交联试验表明贮脂细胞上存在ＶＩＰ－Ｒ的蛋白，分子量约４０ＫＤ。不同浓度的ＶＩＰ（０．１５ｎｍ－１５０ｎｍ）作用于培养的大鼠贮脂细胞，能显著抑制细胞Ⅰ型胶原的分泌并呈量效关系（ｒ＝－０．９８９，ｎ＝６，Ｐ＜０．００１）。ＶＩＰ受体拮抗剂［Ｄ－Ｐ－ｃｌ－Ｐｈｅ６，Ｌｅｕ１７］－ＶＩＰ能减弱ＶＩＰ这一作用。这些结果表明：大鼠贮脂细胞上存在ＶＩＰ－Ｒ；ＶＩＰ通过ＶＩＰ－Ｒ影响贮脂细胞的胶原分泌并可能在肝纤维化的发病过程中起一定的调节作用。     

血管活性肠肽与消化系肿瘤

血管活性肠肽对消化系肿瘤细胞的增殖、分化有调节作用，在胃癌、结肠癌、胰腺癌细胞膜上存在特异性ＶＩＰ受体，ＶＩＰ对它们的增殖，分化调节有促进或抑制效应，这与ＶＩＰ作用于受体后引起细胞内ｃＡＭＰ水平，ＯＤＣ活性，ｃ－ｍｙｃ基因表达改变有关。     

血管活性肠肽对大鼠贮脂细胞Ⅰ型胶原分泌的影响

我们研究发现在传代培养的大鼠贮脂细胞中，不同浓度的血管活性肠肽（Ｖａｓｏａｃｆｉｖｅｉｎｆｅｓｆｉｎａｌｐｅｐｔｉｄｅ，ＶＩＰ）能显著抑制Ⅰ型胶原分泌并呈量效关系。ＶＩＰ受体拮抗剂能减弱ＶＩＰ这一作用，从而更加肯定ＶＩＰ抑制胶原分泌的作用。本研究提示：大鼠贮脂细胞膜上存在ＶＩＰ受体；ＶＩＰ在肝纤维化和肝硬化时浓度升高可能调节肝脏胶原代谢。     

血管活性肠肽对大鼠贮脂细胞I型胶原分泌的影响

我们研究发现在传代培养的大鼠贮脂细胞中，不同浓度的血管活性肠肽（Ｖａｓｏａｃｆｉｖｅｉｎｆｅｓｆｉｎａｌｐｅｔａｉｄｅ，ＶＩＰ）能显著抑制Ｉ型胶原分泌呈量效关系，ＶＩＰ受体拮抗剂能减弱ＶＩＰ这一作用，从而更加肯定ＶＩＰ抑制胶原分泌的作用，本研究提示，大鼠贮脂细胞膜上存在ＶＩＰ受体，ＶＩＰ在肝纤维化和肝硬化时浓度升高可能调节肝脏胶原代谢。     

血管利钠肽减弱去甲肾上腺素对心肌生长的刺激作用

本实验目的在于研究血管利钠肽（ Ｖ Ｎ Ｐ）对去甲肾上腺素（ Ｎ Ｅ）促心肌生长作用的影响,并对其机制进行探讨。分离、培养乳鼠心肌细胞,完全随机分为三组:对照组、 Ｎ Ｅ组和 Ｖ Ｎ Ｐ＋ Ｎ Ｅ组。以 Ｍ Ｔ Ｔ法和总蛋白含量测定法观察各组细胞的生长情况。进而采用放射免疫方法研究了 Ｖ Ｎ Ｐ对细胞内ｃ Ｇ Ｍ Ｐ,ｃ Ａ Ｍ Ｐ水平的影响。结果发现: Ｎ Ｅ（１０－ ７ ｍ ｏｌ／ Ｌ～１０－ ５ ｍ ｏｌ／ Ｌ）可以使培养的乳鼠心肌细胞 Ｍ Ｔ Ｔ Ｏ Ｄ值显著升高（ Ｐ＜ ０．０５ ｖｓ 对照组）,并且具有剂量依赖性。 Ｖ Ｎ Ｐ（１０－ ７ ｍ ｏｌ／ Ｌ）可以显著降低 Ｎ Ｅ（１０－ ６ ｍ ｏｌ／ Ｌ） 刺激的心肌细胞 Ｍ Ｔ Ｔ Ｏ Ｄ值和细胞内总蛋白含量（ Ｐ＜０．０５ ｖｓ Ｎ Ｅ组）。对照组和 Ｎ Ｅ组细胞内ｃ Ｇ Ｍ Ｐ,ｃ Ａ Ｍ Ｐ水平无显著差异,而 Ｖ Ｎ Ｐ（１０－ ７ ｍ ｏｌ／ Ｌ）能升高细胞内ｃ Ｇ Ｍ Ｐ水平,降低ｃ Ａ Ｍ Ｐ水平（ Ｐ＜ ０．０５ ｖｓ对照组、 Ｎ Ｅ组）。提示 Ｖ Ｎ Ｐ能减弱 Ｎ Ｅ对心肌生长的刺激作用,其机制可能与ｃ Ｇ Ｍ Ｐ,ｃ Ａ Ｍ Ｐ等信号转导分子有关。     

高血糖素样肽－1对血糖水平的调控

高血糖素样肽－１（ＧＬＰ－１）具促胰岛素功能，可特异地与β细胞ＧＬＰ－１受体结合，产生ｃＡＭＰ并激活依赖ｃＡＭＰ的蛋白激酶。ｃＡＭＰ升高介导其促胰岛素作用；经依赖ｃＡＭＰ的蛋白激酶对葡萄糖信号通路上关键成分的磷酸化，ＧＬＰ－１增强葡萄糖诱导的胰岛素分泌。输入药理剂量ＧＬｐ－１能改善ＮＩＤＤＭ患者餐后胰岛素分泌反应。ＧＬＰ－１受体激动剂可能是治疗ＮＩＤＤＭ的一条新途径。     

高血糖素样肽—1对血糖水平的调控

高血糖素样肽－１（ＧＬＰ－１）具促胰岛素功能，可特异地与β细胞ＧＬＰ－１受体结合，产生ｃＡＭＰ并激活依赖ｃＡＭＰ的蛋白激酶。ＣＡＭＰ升导其促胰岛素作用；经依赖ＣＡＭＰ的蛋白激酶对葡萄糖信号通路上关键成分的磷酸化，ＧＬＰ－１增强葡萄糖诱导的胰岛互分泌。输入药理剂量ＬＰ－１改善ＮＩＤＤＭ患者餐后胰岛素分泌反应。ＧＬＰ－１受体激动剂可能是治疗ＮＩＤＤＭ的一条新途径。     

血管利钠肽减弱去甲肾上腺素对心肌生长的刺激作用

本实验目的在于研究血管利钠肽对去甲肾上腺素促心肌生长作用的影响，并对其机制进行探讨。分离，培养乳鼠心肌细胞，完全随机分为三组；对照组，ＮＥ组和ＶＮＰ＋ＮＥ组。以ＭＴＴ法和总蛋白含量测定法观察各组细胞的生长情况。进而采用放射免疫方法研究了ＶＮＰ对细胞内ｃＧＭＰ，ｃＡＭＰ水平的影响。／     

血管活性肠肽对神经细胞脂褐素影响的实验研究

采用小鼠神经母细胞癌细胞无血清培养建立神经细胞老化实验研究模型。以显微荧光分光光度术测定的细胞内脂褐素自发荧光值为神经细胞老化指标，观察血管活性肠肽（ＶＩＰ）对实验性神经细胞内脂褐素荧光值的影响。结果发现：ＶＩＰ作用５ｄ可显著升高细胞内的脂褐素荧光值（Ｐ＜０．０１）．提示ＶＩＰ可加速实验性神经细胞的老化过程。     

Effects of vasoactive intestinal peptide on adenosine 3',5'-monophosphate, ornithine decarboxylase, and cell growth in a human colon cell line.

Vasoactive intestinal peptide (VIP) is a widely distributed neuropeptide that has been considered a potential regulator of cell growth and differentiation in various tissues, including the gut. To examine this idea, we used a human colon carcinoma cell line (LoVo) as a model system and measured ornithine decarboxylase (ODC), because this is the rate-limiting enzyme for the formation of polyamines, which are thought to be key factors in regulating cell growth. LoVo cells, grown to about 80% confluence in F-12 medium containing 10% fetal bovine serum, were preincubated for 5 h in low serum medium (1% fetal bovine serum in F-12), and ODC activity was determined by measuring 14CO2 liberated from 14C-labeled ornithine. VIP caused a dose-related biphasic change in ODC, with activity increased at 10 pM, maximal (5-fold increase) at 10 nM, and decreased toward basal at 100 nM to 1 microM. Incubation of cells for 6 days with VIP in low serum medium showed similar changes in cell numbers, with growth being increased by doses in the 1 pM to 100 nM range and decreased at higher doses (greater than or equal to 100 nM). Exposure of cells to 5 mM alpha-difluoromethylornithine blocked both the VIP-induced increase in cell number and the VIP-induced increase in ODC activity. Increased ODC mRNA was detected after 2 h of exposure to VIP, a time at which ODC activity peaked after treatment, and the increase in ODC mRNA caused by VIP was dose-dependent. In related experiments LoVo cells were found to have high affinity VIP receptors (Kd = 0.4 nM), as assessed by examination of [125I]VIP binding in the presence of varying concentrations of unlabeled VIP. Studies of intracellular cAMP revealed a dose-related increase in cAMP in response to VIP (ED50 = 11 pM), and the adenylate cyclase activator forskolin increased both ODC activity and ODC mRNA. The findings support the idea that LoVo cells have VIP receptors linked to cAMP which can stimulate cell growth at least in part by increasing ODC synthesis and activity, thereby altering the production of polyamines. The decreased growth and ODC activity observed with high doses of VIP may involve a second messenger other than cAMP.     

Phorbol ester potentiates VIP-stimulated amylase release in rat pancreatic acini

Vasoactive intestinal peptide (VIP) or 12-O-tetradecanoylphorbol-13-acetate (TPA) individually stimulated amylase release in dispersed rat pancreatic acini. Pretreatment of acini with TPA (10(-6) M) for 5 min at 37 degrees C potentiated their subsequent response to stimulation by VIP at a dose range of 10(-8)-10(-6) M in that the treated pancreatic acini released more amylase than could be accounted for by the additive effects of VIP or TPA acting individually. This potentiation effect of TPA was still evident when isobutyl methylxanthine was given together with VIP. Further, the maximal' dose-response curve to VIP shifted 2 log units to the left (3 x 10(-9) versus 3 x 10(-7) M). The TPA preincubation was found also to potentiate VIP-stimulated net increases in intracellular cyclic AMP (cAMP) levels. A close correlation existed between the net releases of amylase and the net increases in intracellular cAMP levels (r = 0.97). This suggested that TPA potentiated the response of rat pancreatic acini to VIP by modulating the cAMP system. The TPA as a potent activator of protein kinase C may act as a modulator of the adenylate cylase-cAMP system in rat pancreatic acini.     

Effect of GHRH and peptides from the vasoactive intestinal peptide family on cAMP production of human cancer cell lines in vitro.

Antagonistic analogs of GHRH inhibit growth of various human cancers both in vivo and in vitro. To elucidate the mechanism of direct action of the antagonistic analogs of GHRH on tumor cells, cultured human cancer cells were exposed to GHRH, vasoactive intestinal peptide (VIP), secretin, glucagon, neuropeptide-Y (NPY), pituitary adenylate cyclase-activating peptide (PACAP), and VIP analogs in a superfusion system, and changes in cAMP and IGF-II release from the cells were measured. Various human cancer cell lines, such as mammary (MDAMB-468 and ZR-75-1), prostatic (PC-3), pancreatic (SW-1990 and Capan-2), ovarian (OV-1063), and colorectal (LoVo) responded to pulsatile stimuli with GHRH (0.5-20 nM), VIP (0.02-10 nM), and PACAP-38 (0.05-5 nM) with a rapid, transient increase in cAMP release from the cells. The VIP antagonist, PG-97-269, and the adenylate cyclase inhibitor, MDL-12330A, but not SQ-22536 or pertussis toxin, blocked the cAMP responses to these peptides. Stimulation of the cells with 100 nM secretin, glucagon or NPY did not alter the cAMP release. Our results suggest that GHRH receptors different from the type expressed in the pituitary are involved in mediating these effects. As cAMP is a potent second messenger controlling a wide variety of intracellular functions, including those required for cell growth, our results indicate that GHRH might have a direct stimulatory effect on growth of human cancers. Blockade of the autocrine/paracrine action of GHRH with its antagonistic analogs may provide a new approach to tumor control.     

Vasoactive intestinal peptide: A potent stimulator of adenosine 3′:5′-cyclic monophosphate accumulation in gut carcinoma cell lines in culture

Vasoactive intestinal peptide (VIP) is a potent and efficient stimulator of adenosine 3':5'-cyclic monophosphate (cAMP) accumulation in a human colon carcinoma cell line, HT 29. cAMP accumulation is sensitive to a concentration of VIP as low as 3x10(-12) M. Maximum VIP-induced cAMP levels were observed with 10(-9) M VIP and are about 200 times above the basal levels. Half-maximum cAMP production was obtained at 3x10(-10) M VIP. (125)I-Labeled VIP was found to bind to HT 29 cells; this binding was competitively inhibited by concentrations of unlabeled VIP between 10(-10) and 10(-7) M. Half-maximum inhibition of binding was observed with 2x10(-9) M VIP. Secretin also stimulated cAMP accumulation in HT 29 cells, but its effectiveness was 1/1000 that of VIP. The other peptides tested at 10(-7) M, such as insulin, glucagon, bovine pancreatic polypeptide, somatostatin, octapeptide of cholecystokinin, neurotensin, and substance P, did not stimulate cAMP accumulation. Prostaglandin E(1) and catecholamines stimulated cAMP production but were 1/2.3 and 1/5.5 as efficient as VIP, respectively. Another malignant cell line from the gut, the human rectal tumor cell line HRT 18, is also sensitive to VIP. In HRT 18 cells, VIP stimulated cAMP accumulation with a maximal effect at 10(-8) M; half-maximum stimulation was observed at about 10(-9) M. These results demonstrate the presence of VIP receptors in two malignant human intestinal cell lines (HT 29 and HRT 18) in culture and provide a model for studying the action of VIP on cell proliferation.     

Identification of cells responding to vasoactive intestinal peptide by measuring intracellular cyclic adenosine monophosphate in human colonic mucosa

BACKGROUND: Although there is great deal of evidence suggesting that vasoactive intestinal peptide (VIP) has immunomodulating effects on human colonic lamina propria mononuclear cells (LPMC), it remains unclear which type of cell carries functional VIP receptors. In this study we investigated the presence of functional VIP receptors by measuring intracellular cyclic adenosine monophosphate (cAMP) in isolated epithelial cells, bulk LPMC, T cells, and macrophages in human colonic mucosa. METHODS: Epithelial cells and LPMC were isolated from non-pathologic segment of colonic mucosa of surgical specimens from five patients with colonic cancer. Mucosal T cells and macrophages were further isolated from LPMC. Each cell population was cultured with various concentration of VIP for 60 min at most. Then, intracellular cAMP was extracted and measured by enzyme-linked immunoassay. RESULTS: When isolated epithelial cells were examined, VIP increased intracellular cAMP in a dose-dependent fashion, as observed in HT-29 cells used as a positive control. In contrast, the concentration of cAMP was essentially stable in response to VIP when isolated LPMC were examined. This was the case even when separated T cells and macrophages were individually investigated. To evaluate the possible effects of enzyme digestion for LPMC isolation on the VIP response. HT-29 cells were precultured with collagenase and deoxyribonuclease (DNase 1), resulting in less enhancement of cAMP by VIP. CONCLUSIONS: In this study we failed to show VIP-responsive enhancement of cAMP in mucosal immune cells, suggesting that epithelial cells may be major effector cells of VIP in human colonic mucosa.     

垂体腺苷酸环化酶激活多肽对胰腺癌细胞的生长调控

目的 观察垂体腺苷酸环化酶激活多肽（pituitary adenylate cyclase activating polypeptide,PACAP)对人胰腺癌细胞株的生长调控作用;并确定神经鞘磷脂是否作为第二信使参与受体后信息传导。方法 人胰腺癌细胞株JF305,HS766T,ASPC－1进行细胞培养,传代。分别加入不同浓度的PACAP1－38（10^-6-10^-12mol/L)于三种癌细胞中。应用MTT法观察细胞增程度。薄层层析法测定细胞神经鞘磷脂。放射免疫法测定细胞内cAMP含量。Fura-2/AM测定细胞内游离Ca^2 浓度。结果 PACAP1－38促进JF305,HS766T,ASPC－1细胞的生长;PACAP1－38增加细胞内神经鞘磷脂、cAMP、Ca^2 的生长;生长抑素可明显抑制PACAP1－38诱导的JF305细胞的生长等作用。结论 PACAP1－38促进人胰腺癌细胞株的增殖。PACAP受体后信息传递途径;（1）腺苷 酸环化酶途径;（2）钙－钙调素途径。神经鞘磷脂作为第二信使也参与此过程。     

Identification of Cells Responding to Vasoactive Intestinal Peptide by Measuring Intracellular Cyclic Adenosine Monophosphate in Human Colonic Mucosa

Background: Although there is great deal of evidence suggesting that vasoactive intestinal peptide (VIP) has immunomodulating effects on human colonic lamina propria mononuclear cells (LPMC), it remains unclear which type of cell carries functional VIP receptors. In this study we investigated the presence of functional VIP receptors by measuring intracellular cyclic adenosine monophosphate (cAMP) in isolated epithelial cells, bulk LPMC, T cells, and macrophages in human colonic mucosa. Methods: Epithelial cells and LPMC were isolated from non-pathologic segment of colonic mucosa of surgical specimens from five patients with colonic cancer. Mucosal T cells and macrophages were further isolated from LPMC. Each cell population was cultured with various concentration of VIP for 60 min at most. Then, intracellular cAMP was extracted and measured by enzyme-linked immunoassay. Results: When isolated epithelial cells were examined, VIP increased intracellular cAMP in a dose-dependent fashion, as observed in HT-29 cells used as a positive control. In contrast, the concentration of cAMP was essentially stable in response to VIP when isolated LPMC were examined. This was the case even when separated T cells and macrophages were individually investigated. To evaluate the possible effects of enzyme digestion for LPMC isolation on the VIP response, HT-29 cells were precultured with collagenase and deoxyribonuclease (DNase I), resulting in less enhancement of cAMP by VIP. Conclusions: In this study we failed to show VIP-responsive enhancement of cAMP in mucosal immune cells, suggesting that epithelial cells may be major effecter cells of VIP in human colonic mucosa.     

Somatostatin inhibits vasoactive intestinal peptide-stimulated cyclic adenosine monophosphate accumulation in GH pituitary cells

Somatostatin (SRIF) has previously been shown to inhibit both basal and hormone-stimulated PRL secretion from GH4C1 cells, a clonal strain of rat pituitary tumor cells. In this study we examined the ability of SRIF to modulate cAMP accumulation in GH4C1 cells to determine whether such alterations mediate its biological effects. SRIF did not cause statistically significant changes in basal cAMP accumulation. Of six PRL secretagogues examined, only vasoactive intestinal peptide (VIP) increased cAMP accumulation significantly: TRH, bombesin, epidermal growth factor, insulin, and the tumor promoter, phorbol-12,13-dibutyrate were without effect. When SRIF was added simultaneously with VIP, it inhibited maximal VIP-stimulated cAMP accumulation (55 +/- 3%, mean +/- SE) without changing the ED50 for VIP (3.0 +/- 0.2 nM). Inhibition by SRIF was not due to altered kinetics of VIP stimulation, since the half-time for VIP-stimulated cAMP accumulation was 2 min both in the absence and presence of 100 nM SRIF. SRIF did not inhibit isobutylmethylxanthine-stimulated cAMP accumulation, and the presence of 0-10 mM isobutylmethylxanthine did not alter the inhibitory effect of SRIF on VIP-stimulated cAMP accumulation. Therefore, SRIF must act primarily to modulate VIP activation of adenylate cyclase activity. Inhibition of VIP-stimulated cAMP accumulation occurred at concentrations of SRIF (ID50 = 1.2 +/- 0.1 nM) close to the equilibrium dissociation constant for receptor binding (Kd = 0.6 +/- 0.2 nM). Furthermore, the potencies of a series of SRIF analogs to inhibit VIP-stimulated cAMP accumulation correlated with the apparent Kd of each peptide for binding to the SRIF receptor. In addition, SRIF did not reduce VIP-stimulated cAMP accumulation in GH(1)2C1 cells, which lack SRIF receptors. We conclude that SRIF inhibits VIP-stimulated cAMP accumulation by a receptor-mediated process that may be causally related to the ability of SRIF to inhibit VIP-dependent PRL secretion.     

See-saw signal processing: reciprocal effects of stimulus deprivation on vasoactive intestinal peptide-stimulated adenosine 3',5'-monophosphate and guanosine 3',5'-monophosphate accumulation in rat pinealocytes.

In the present study the effects of stimulus deprivation on vasoactive intestinal peptide (VIP)- and alpha 1-adrenergically mediated amplification of VIP-stimulated cAMP and cGMP accumulation were examined. Dispersed pinealocytes were prepared from either Sprague-Dawley rats maintained for 2 weeks in a normal lighting schedule providing 14 h of light/day (LD cells) or from animals maintained in constant lighting (LL cells). LL treatment enhanced the VIP-stimulated cAMP response up to 2-fold, while reducing the peak VIP-stimulated cGMP by 70%. In LL cells, phenylephrine potentiated the VIP-stimulated cAMP response, but did not potentiate the VIP-stimulated cGMP response. Potentiation of the cAMP response to VIP can be produced in LD cells by treatment with agents that elevate intracellular Ca2+ (depolarizing concentrations of K+ or A23187) or an activator of protein kinase-C [14 beta-phorbol 12-myristate 13-acetate (PMA)]. LL treatment abolished the potentiating effects of K+ or A23187 on cAMP and cGMP responses in VIP-treated cells. In contrast, LL treatment augmented the PMA potentiation of VIP-stimulated cAMP response. The potentiation effects of PMA and K+ on the cGMP response in VIP-treated cells, however, were suppressed by LL treatment. To further investigate the involvement of postreceptor mechanisms, forskolin was used to stimulate pineal cAMP and cGMP accumulation. LL treatment had similar effects on the forskolin-stimulated cyclic nucleotide responses, with one exception. Depolarizing concentrations of K+ potentiated the forskolin-stimulated cAMP response while having no effect on the VIP-stimulated cAMP responses. These findings suggest that LL treatment results in a larger VIP-stimulated cAMP response, while its effect on the cGMP response is inhibitory. LL treatment appears to inhibit a step distal to elevation of intracellular Ca2+ which is of importance to the alpha 1-adrenergic potentiation of VIP-stimulated cAMP and cGMP responses.     

Pituitary adenylate cyclase-activating polypeptide receptors mediating insulin secretion in rodent pancreatic islets are coupled to adenylate cyclase but not to PLC

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a potentiator of glucose-induced insulin secretion. PACAP binds to a PACAP-specific receptor (PAC1) and to VPAC receptors (VPAC1 and VPAC2), which share high affinity for vasoactive intestinal polypeptide (VIP). In the present study, the molecular expression of PACAP receptor isoforms and the signaling pathways involved in the insulin secretory effect of PACAP were investigated in isolated rat and mouse pancreatic islets. mRNA encoding PAC1-short, -hop, and -very short variants, as well as VPAC1 and VPAC2, were expressed in pancreatic islets. PACAP and VIP were equipotent in potentiating glucose-induced insulin release. Both peptides were also equipotent in increasing cAMP production, but PACAP was more efficient than VIP. Unlike carbachol, PACAP and VIP had no effect on inositol phosphate production. In the PAC1-deficient mouse, the insulinotropic effect of PACAP was reduced, and its differential effect on cAMP production was abolished, whereas the effects of VIP remained unchanged. These results clearly show that the insulinotropic effect of PACAP involved both VPAC and PAC1. The PAC1 variants expressed in rat and mouse pancreatic islets seem to be coupled to adenylate cyclase but not to PLC.