Monoclonal antibody HISL-19 as an immunocytochemical probe for neuroendocrine differentiation. Its application in diagnostic pathology.

The monoclonal islet cell antibody HISL-19 was generated after immunization of BALB/c mice with human islet cell preparations. Besides reactivity with all cells of the human pancreatic islet, MAb HISL-19 also reacted with other cells of the diffuse neuroendocrine system, including anterior pituitary cells, C cells of the thyroid, endocrine cells of the gut and bronchus, the adrenal medulla, and central and peripheral neurons. In this study the authors screened a series of 53 neuroendocrine and 71 nonneuroendocrine tumors for their reactivity with MAb HISL-19 using an indirect immunoperoxidase technique on formalin-fixed and Paraplast-embedded sections. MAb HISL-19 reacted strongly with all insulomas (10), carcinoids (8), C-cell carcinomas of the thyroid (8), pituitary adenomas (6), neuroendocrine carcinomas of the skin (4), paragangliomas of the carotid body (3), and pheochromocytomas (2) tested. Neuroblastomas (3), oat-cell carcinomas of the lung (2), and melanomas (4) exhibited only very few immunoreactive cells scattered throughout the tumor or remained unstained with MAb HISL-19. With the exception of one lobular carcinoma of the breast (1/3), one adenocarcinoma of the endometrium (1/4), and one adenocarcinoma of the stomach (1/6), nonneuroendocrine tumors were negative with MAb HISL-19. Biochemical findings obtained by SDS-PAGE, "Western" immunoblotting, immunoaffinity chromatography, and absorption experiments indicate that the MAb HISL-19-defined antigen is not related to neuron specific enolase. Because the epitope recognized by MAb HISL-19 is well preserved in formalin-fixed and routinely processed tissues, this monoclonal antibody finds potential applications in diagnostic pathology as an indicator for neuroendocrine cells and their neoplasms.     

Identification of monoclonal antibodies to pancreatic islet cells by immunoperoxidase staining

Immunoperoxidase staining and enzyme-linked immunosorbent assay (ELISA) were used to identify monoclonal antibodies that reacted with pancreatic islet cells. All monoclonal antibodies produced against isolated human or rat pancreatic islets including one mouse autoantibody reacted with pancreatic islets in formalin-fixed pancreas sections, but not with rat kidney or thyroid. Reactivity was also found with suspensions of normal rat islet cells and rat insulinoma cells using a 3-stage immunoperoxidase procedure and an ELISA technique. Differences were observed in staining intensity between the various antigenic substrates tested suggesting variable cross-reactivity and/or number of epitopes. The sensitivity of the immunoperoxidase technique proved to be favourable for identification of monoclonal antibodies that recognize cellular constituents such as islet cell antigens present in low concentrations.     

Histogenesis and ultrastructure of pancreatic islet graft microvasculature. Evidence for graft revascularization by endothelial cells of host origin.

In previous studies we have demonstrated that syngeneic and xenogeneic pancreatic islet grafts are revascularized within a 10 to 14-day period after transplantation. With the combined use of intravital and electron microscopy, as well as immunohistochemistry using a set of species-specific or -crossreacting antibodies to endothelial cell antigens, we investigated 1) the origin of the endothelium of the newly formed capillaries in free pancreatic islet isografts (hamster-->hamster) and xenografts (rat-->hamster), and 2) the ultrastructural characteristics of these microvessels. Intravital microscopy demonstrated that newly formed microvessels grow from the vascular bed of the host muscle tissue into the islet grafts. Immunohistochemical analysis of host tissue and transplanted islets with antibodies against factor VIII (recognizing both hamster and rat factor VIII), bovine PECAM-1 (CD31; endoCAM, crossreacting with hamster but not rat PECAM-1), and rat ICAM-1 (CD54, non-crossreacting with hamster ICAM-1) showed that the transplanted rat islets were revascularized by endothelium of hamster (host) origin. At an ultrastructural level, the endothelial lining of the newly formed microvessels showed diaphragmatic fenestration, a characteristic feature of endothelial cells of pancreatic islets in situ. On the basis of these findings we suggest that pancreatic islet transplantation may take a unique position in the field of organ transplantation, since the generally proposed mechanisms of endothelial cell-dependent antigen recognition as a trigger of graft rejection may not be transferred to islet grafts, containing microvessels lined by endothelial cells of host origin.     

The fate of intraportally transplanted islets in diabetic rats. A morphologic and immunohistochemical study.

Streptozotocin-induced diabetes in the rat can be reversed by the transplantation of isogenic islets of Langerhans from neonatal donors. We studied the morphology of intraportally transplanted islets with the aid of the immunoperoxidase staining technique to identify insulin-, glucagon-, somatostatin-, and pancreatic polypeptide-containing cells at 24 hours, 48 hours, 1 week, 2 weeks, 4 weeks, 39 weeks, and 65 weeks after transplant. Embolized pancreatic tissue, composed of approximately 80% acini and 20% islets, is initially distributed throughout the liver mainly to terminal branches of the portal system. Endothelialization and organization occur rapidly with the smaller fragments and within the first 4 weeks for larger thrombi. Exocrine pancreatic elements largely disappear as islet cells move into the hepatic lobules from the portal spaces. At 65 weeks after transplant, all islet cell types can be identified within large complex islet structures. The results of this study establish the survival and continued function of all known rat pancreatic islet cell types long after transplantation and support the theory that islet transplantation may represent the most physiologic replacement of hormonal deficiencies in the diabetic recipient.     

胎鼠胰腺干细胞与胰岛联合移植保护胰岛

背景：胰腺干细胞可在体外维持胰岛的结构,减少胰岛细胞坏死及凋亡,延长胰岛的体外存活时间,保护胰岛的活性。 目的：探索胎鼠胰腺干细胞与胰岛共移植体内保护移植胰岛,提高胰岛移植疗效的可行性。 方法：将成年大鼠35只随机等分为联合移植组、单独胰岛移植组、单纯胰腺干细胞移植组、模型组及对照组,前4组均腹腔注射链脲佐菌素-柠檬酸盐缓冲液建立糖尿病模型。联合移植组、单独胰岛移植组、单纯胰腺干细胞大鼠分别在左侧肾包膜下移植分离纯化孕16 d SD大鼠胎鼠胰腺干细胞和/或成年SD大鼠胰岛。 结果与结论：联合移植组大鼠移植后5 d内血糖可降至正常,血浆胰岛素达到正常水平,胰岛存活时间(18.2±2.4) d;单独移植组大鼠血糖可于移植后1周内降至正常,胰岛存活时间(14.4±2.1) d;两组胰岛存活时间比较差异有显著性意义(P < 0.05)。而其他组糖尿病大鼠血糖均未能降至正常范围。说明胎鼠胰腺干细胞与胰岛共移植可延长胰岛体内存活时间,保护胰岛功能,提高移植疗效。中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程全文链接：     

Oxidation of [1,12-14C]dodecanedioic acid by rat pancreatic islets

Several aliphatic dioic acids were recently reported to stimulate insulin release in isolated rat pancreatic islets incubated at close-to-physiological D-glucose concentrations. In order to gain insight into the mode of action of these acids in pancreatic islet B-cells, the oxidation of [1,12-14C]dodecanedioic acid (5.0 mM) was now measured in rat islets. Expressed as pmol of [1, 12-14C]dodecanedioic acid equivalent, the production of 14CO2 was close to 1.0 pmol/islet per 120 min, representing about 8% of that attributable to the oxidation of D-[U-14C]-glucose (8.3 mM). The dioic acid and the hexose failed to exert any significant reciprocal effect upon their respective oxidation rate. These findings support the view that the insulinotropic action of dodecanedioic acid, and presumably other aliphatic dioic acids, is causally linked to their capacity to act as nutrients in pancreatic islet cells.     

Functional integrity of dispersed islet cells attached to a two-dimensional microsupport

Dispersed rat pancreatic islet cells were cultured overnight in the presence of polystyrene two-dimensional microsupports. About 1.7-1.9x10(6) cells attached to the microsupports (832 cm2) were found to display both an insulin content and secretory response to D-glucose and/or theophylline comparable to those otherwise found in cultured free islet cells. It is proposed that advantage could be taken of this approach to study the function of islet cells attached in a standardized number to such two-dimensional microsupports.     

短期持续高糖输注诱导胰岛β细胞增殖的大鼠模型建立

目的：建立高糖输注诱导胰岛β细胞增殖的大鼠模型,为研究胰岛β细胞增殖的机制提供研究平台。方法：SD大鼠颈静脉插管后用输液泵连续输注72h的50%葡萄糖和0.45%的NaCl,用BrdU掺入和标记增殖蛋白ki67检测大鼠胰岛β细胞增殖情况,并检测增殖相关基因的表达。结果：输注50%葡萄糖组的大鼠与NaCl组比较胰岛β细胞BrdU和ki67阳性细胞明显增多,增殖相关基因ccnd2,c-myc表达增高,P27降低。结论：通过持续的高糖输注72h可建立胰岛β细胞增殖的大鼠模型。     

Major histocompatibility complex protein expression on pancreas and pancreatic islet endocrine cell subsets

To determine which cells in the human and rat pancreas and islets express class I and II histocompatibility complex proteins, double indirect immunofluorescence and the Staphylococcus aureus rosette method were used. Islet preparations used permitted positive endocrine and class I or II protein identification. Class I and II proteins were expressed in pancreatic vascular endothelium and passenger cells of the mononuclear cell type. Antibodies directed to class I or beta 2 microglobulin reacted with dispersed islet B, A, and D cells, whereas class II protein antibodies were associated with only islet B and A cells. Islet B-cell class II proteins decreased after 20 days of in vitro culture. These results suggest that 1) a variety of pancreas and islet nonendocrine cells can express class I and II proteins, 2) normal pancreatic islet endocrine cells not only express class I proteins but also class II proteins, and 3) in vitro islet culture results in reduced expression of class II proteins by islet B cells.     

Effects of interleukin-15 on suppression of rat pancreatic islets in vitro induced by proinflammatory cytokines

The cytokine IL-15 might contribute to inflammatory processes, but also act as an inhibitor of apoptosis in different cell lines. Furthermore, it has been reported that islet cells express IL-15 after exposure to proinflammatory cytokines, which could indicate a defence reaction. We aimed in this study to investigate if IL-15 could influence cell death and/or functional impairment of rat pancreatic islets induced by in vitro exposure to a combination of cytokines (25 U/ml IL-1beta+1000 U/ml IFN-gamma+1000 U/ml TNF-alpha). The effect of IL-15 itself on the function of rat pancreatic islets was also studied. Isolated rat islets were exposed for 24 h to IL-15 at different concentrations in the presence or absence of the cytokine mixture. The cytokines caused a strong inhibition of glucose-stimulated insulin release and the glucose oxidation rates. IL-15 (0.1-10 ng/ml) could not prevent the functional suppression caused by these effects. The cytokine combination caused a decline in whole islet DNA content and a marked increase in non-viable cells analysed by propidium iodide (PI) and annexin V staining. However, there was no significant decrease in whole islet DNA content when IL-15 (0.1 or 1.0 ng/ml) was present together with the cytokine mixture. On the other hand, IL-15 failed to influence the increase in cell death after PI and annexin V staining. If anything, IL-15 alone had a slight stimulatory effect (glucose oxidation rate) on islet cells. In conclusion, we can not exclude that IL-15 might antagonize some cytokine mediated cell death in islet cells, however, IL-15 fails to counteract functional suppression induced by cytokines.     

Morphological changes of isolated rat pancreatic islets: a structural, ultrastructural and morphometric study

Improved techniques for pancreatic islet extraction can yield a reasonable number of transplantable cells. However, the isolation and purification process may damage the islets and impair their physiological functions. The aim of this study was to determine the effect of the isolation procedure on the structure of isolated islets and to correlate this with their functionality. Islets were isolated from rat pancreata and purified by Eurocollins-Ficoll discontinuous density gradient processing, and then processed for light microscopy, and scanning and transmission electron microscopy. Morphometric analysis was also performed. Islet functionality was determined by reversal of streptozotocin-induced diabetes and the intraperitoneal glucose tolerance test in a syngeneic rat model of pancreatic islet transplantation. Fragments of variable size and shape comprised a relatively large proportion (26%) of the isolated endocrine tissue. Isolated islets showed slight alterations of cell ultrastructure. Major damage (including breakage of the plasma membrane) and loss of cells were observed in the peripheral cells of the isolated islets. An equal mass of islet equivalent (IEq, islets with an average diameter of 150 microm), but with a different islet equivalent/islet number ratio, was transplanted in diabetic animals. When larger and more complete islets were transplanted (higher ratio), better function of the graft was observed by reversal of hyperglycaemia and response to the glucose tolerance test as compared with the functionality and response of smaller (fragmented) islets transplanted (lower ratio). Digestion, trauma and hypoxia during isolation are responsible for qualitative and quantitative changes of isolated islets. Alterations in normal secretory function after the transplant were related to lower islet equivalent/islet number ratio. The incomplete integrity of the islets may explain the failure of the fine glycaemic metabolic regulation.     

Degranulation effect of ferric nitrilotriacetate (Fe3+-NTA) on the pancreatic islet beta-cells: its acute toxic effect on glucose metabolism

A single injection of ferric nitrilotriacetate (Fe3+-NTA) caused a transitory increase in plasma immunoreactive insulin (IRI) and plasma immunoreactive glucagon (IRG) in rats. They reached maximum levels at 2 days after injection and returned to the normal range at 10 days. At 2 days after Fe3+-NTA injection, blood glucose level was normal but the glucose tolerance test (GTT) was impaired. There was a further increase in plasma IRI level and IRG level was suppressed after glucose loading. At 10 days after Fe3+-NTA injection, glucose tolerance was normal and IRI also returned to the normal range. No degenerative changes were found on H.E.-stained rat pancreatic tissue sections after Fe3+-NTA injection. Histochemical staining, however, showed a reduction in beta-granules and heavy metals (Timm's granules) from islet cells in the central area of the rat pancreatic islet 1 to 3 days after injection of Fe3+-NTA. The fading remained in some islets even at 10 days after injection, but by then the beta-granule distribution was restored in most islet cells. The results indicate a single Fe3+-NTA injection induced transitory instability of the pancreatic islet beta-cell granules and the glucose intolerance with a hyperresponse of IRI.     

Glycogen accumulation in cultured tumoral or normal pancreatic islet and acinar cells.

Tumoral pancreatic islet cells of either the RINm5F or INS-1 cell lines, when cultured in the presence of 30.0 mM D-glucose, accumulate about 50 times more glycogen than tumoral pancreatic acinar cells of the AR42J line cultured under the same experimental conditions. Expressed per nl of intracellular water, the glycogen content of the RINm5F or INS-1 cells is even higher than that found in rat pancreatic islets also cultured under the same experimental conditions. Moreover, at variance with normal islet cells, tumoral islet cells do not require to be exposed to a high concentration of D-glucose to accumulate large amounts of glycogen. Based on these findings, it is proposed that the labelling of the glycogen pool, e.g. by 11C-labelled D-glucose or 2-deoxy-2-[18F]fluoro-D-glucose, may allow identification and localization of insulinomas in the pancreatic gland by a non-invasive imaging procedure.     

Monoclonal Antibodies against Pancreatic Islet-Cell-Surface Antigens Selected by Flow Cytofluorometry

BALB/c mice were immunized with human islets of Langerhans, and spleen cells from two mice, found to develop cell-surface antibodies against insulin-producing rat islet tumour RIN-5F cells, were fused with mouse myeloma cells. Antibody-producing hybrids were cloned on the basis of their production of surface antibodies reactive with paraformaldehyde-fixed RIN-5F cells by indirect immunofluorescence analysis in the fluorescence-activated cell sorter. Among 236 primary clones, eight stable cell lines producing islet-cell-surface antibodies were eventually cloned. Antibody 2G3 (IgM) reacted with viable normal rat islet cells and high insulin-producing rat islet tumour RIN5-A2 cells, while 3G3 (IgM) only reacted with RIN5-A2 cells. Antibody beta B1 (IgG1) reacted with all islet cells tested and detected an Mr21k component in immunoblotting experiments with RIN-5AH cell plasma membrane proteins electrophoretically transferred to nitrocellulose filters. Antibody 7F6 (IgM) reacted with all islet and non-islet cells tested and detected bands of Mr 66k and 27k by immunoblotting. Antibodies gamma B3, gamma B6, gamma C2, and 6B1 (all IgM) showed varying degrees of binding to different islet cells, but reacted only weakly with non-islet human cells. It is concluded that monoclonal antibodies against pancreatic islet cells may define specific endocrine islet-cell-surface determinants.     

胰岛细胞移植磁共振扫描活体示踪的序列优化

背景：细胞移植领域仍缺乏有效的方法活体示踪观察细胞移植后体内的转归,随着分子影像学的发展使磁共振移植细胞活体示踪技术成为可能。 目的：对胰岛细胞移植磁共振成像活体示踪的扫描序列和参数进行优化,提高胰岛细胞移植磁共振扫描活体示踪结果的可靠性。 方法：通过SD大鼠门静脉输注超顺磁氧化铁纳米颗粒菲立磁标记的胰岛细胞,固定于7 cm小动物专用线圈,在临床1.5T MR上分别采用SE T1W、FSE T2W、FGRE、SPGR对移植前后大鼠肝脏进行扫描,观察输注胰岛细胞前后研究部位的信号变化,并比较不同序列SPIO标记胰岛细胞与周围肝脏组织的对比度噪声比。 结果与结论：FGRE和SPGR都可以较好地克服腹部呼吸运动伪影,敏感地显示超顺磁氧化铁纳米颗粒菲立磁标记的胰岛细胞。标记胰岛细胞在SD大鼠肝脏MRI图像上表现为斑点状的信号减低区,广泛分布于肝脏各部位。结果显示磁共振扫描可以对肝内胰岛移植物进行有效示踪,序列的选择至关重要。     

Uptake of D-mannoheptulose by normal and tumoral pancreatic islet cells

D-mannoheptulose was recently proposed as a possible tool to label preferentially insulin-producing cells in the pancreatic gland. In the present study, D-[3H]-mannoheptulose uptake by rat pancreatic islets or dispersed islet cells was found to represent a time-related and temperature-sensitive process inhibited by cytochalasin B. This mould metabolite also inhibited the efflux of D-[3H]-mannoheptulose from prelabelled islets. After 60 min incubation at 37 degrees C, the apparent intracellular distribution space of the tritiated heptose was close to or somewhat higher than that of D-[5-3H]glucose and close to 50% of the intracellular 3HOH space. It was further enhanced by D-glucose and a high concentration of 10 mM of D-mannoheptulose. The uptake of D-[3H]mannoheptulose was much lower however than that of D-[3H]mannoheptulose hexaacetate. As judged from the fate of D-mannoheptulose hexa[2-14C]acetate, the latter ester was efficiently hydrolyzed in the islet cells. The internalization of D-[3H]mannoheptulose (or its ester) coincided with the generation of tritiated acidic metabolites, reflecting phosphorylation of the heptose. The situation found in normal islet cells sharply differed from that found in tumoral islet cells of either the RINm5F or INS-1 line, in which the apparent distribution space of D-[3H]mannoheptulose represented only about 3 and 9%, respectively, of the intracellular 3HOH space. These results indicate that the entry of D-mannoheptulose into islet cells represents a carrier-mediated process, possibly mediated at the intervention of GLUT2 and, hence, provide further support to the possible use of a suitable D-mannoheptulose analog as a tool for the preferential labelling of insulin-producing cells in the pancreatic gland.     

结扎大鼠胸导管诱发胰组织结构的形态学变化

目的 观察胰淋巴淤滞动物模型胰组织结构变化和胰淀肽沉积情况,探讨淋巴淤滞对胰组织细微和超微结构的影响. 方法 10月龄大鼠20只,采用腹部结扎大鼠胸导管,建立胰淋巴淤滞动物模型,造模后6个月取材,部分胰组织经石蜡包埋切片,行HE和刚果红染色;部分经冷冻切片,行免疫组织化学染色和光镜观察;部分标本进行透射电镜样品制备和观察. 结果 HE和刚果红染色切片光镜观察显示,胰腺小叶间隙增宽,呈明显的结缔组织增生、脂肪堆积;胰岛淡染或着朱红色,组织间隙明显增宽.免疫组织化学染色切片光镜观察显示,在胰岛及其周围,呈现胰淀肽强阳性棕褐色着色反应.超薄切片透射电镜观察显示,胰腺小叶间隙增宽,可见血管和扩大的淋巴管;胰岛细胞间隙增宽,细胞间隙内可见大量脂滴样物质和胶原原纤维样结构.结论 胸导管结扎可导致胰淋巴引流障碍,引起胰淋巴管扩张,结缔组织间隙增宽,脂肪堆积,胰岛细胞间隙扩大,胰淀肽沉积等,这些结构变化可能影响胰岛的功能.     

RAGE ligands induce apoptotic cell death of pancreatic β-cells via oxidative stress

Activation of the receptor for advanced glycation endproducts (RAGE) by its ligands leads to cellular damage contributing to diabetic complications. It is not clearly known whether RAGE ligands influence pancreatic β-cells. In this study, we investigated the expression of RAGE in islet cells and the effect of RAGE ligands, S100b and HMG-1, on islet cells. RAGE was expressed in INS-1 cells and isolated rat and human islets at mRNA and protein levels. RAGE and its ligand, S100b, were detected on islet cells in 28-week-old diabetic OLETF rats. Both S100b and HMG-1 induced apoptotic cell death of INS-1 and islet cells. This INS-1 cell apoptosis was accompanied by increased intracellular oxidative stress and inhibited by antioxidants or a NADPH oxidase inhibitor. Our results showing S100b/RAGE expression on islets of diabetic rat model and RAGE ligands-induced islet cell apoptosis via NADPH oxidase-mediated ROS generation suggest that RAGE ligands-RAGE interaction may contribute not only to the development of diabetic complications but also to the progressive β-cell loss in type 2 diabetes by inducing oxidative stress.     

Exendin-4对不同热缺血时间心死亡供体大鼠胰岛功能的影响

背景：心死亡供体大鼠供胰的利用不可避免地经过热缺血损伤,因此热缺血时间的长短对获得的胰岛数量及功能有重要影响。 目的：观察Exendin-4对不同热缺血时间心死亡供体大鼠胰岛功能的影响。 方法：大鼠胰岛细胞体外培养,根据实验条件随机分为3大组：热缺血0,30和45 min组,每组又分为2亚组,其中对照组为胰岛细胞培养24 h;实验组为10 nmol/L Exendin-4与胰岛细胞培养24 h。应用双硫踪染色来计算分离胰岛数目并判断所提胰岛的纯度;丫啶橙/溴乙啶染色检测胰岛存活,胰岛素释放实验检测胰岛功能。 结果与结论：随着热缺血时间的延长各组获得胰岛细胞的数量、纯度、存活率及功能逐渐降低。热缺血0 min组、30 min组、45 min组加入10 nmol/L Exendin-4培养24 h后分离、纯化的胰岛数量及纯度、活性均比未加入Exendin-4培养的对照组有所提高,热缺血30 min及热缺血45 min组中的实验组与对照组相比差异均有显著性意义(P < 0.05)。提示Exendin-4对不同热缺血时间心死亡供体大鼠胰岛细胞具有保护作用,能减少胰岛细胞凋亡,改善胰岛的存活与功能;Exendin-4的使用可能成为胰岛移植早期缺血的边缘供体预处理的有效方法。 中国组织工程研究杂志出版内容重点：肾移植;肝移植;移植;心脏移植;组织移植;皮肤移植;皮瓣移植;血管移植;器官移植;组织工程全文链接：     

Immunocytochemical Localization of Glucose Transporter-2 (GLUT-2) in Pancreatic Islets and Islet Cell Tumors

Glucose is a major metabolic fuel in mammals and is transported into organs and cells by a facilitated diffusion which involves binding of glucose to glucose transporters (GLUTs). Among several GLUTs so far indentified, GLUT-2 is specifically localized immunocytochemically in beta-islet cells. Using immunocytochemical staining, normal pancreases and 27 cases of islet cell tumors, including insulinomas, gastrinomas, glucagonomas, pancreatic polypeptide-omas (PPomas), and a nonfunctioning islet cells tumor, were systematically stained for four different pancreatic hormones, gastrin, and GLUT-2. GLUT-2 staining in beta-islet cells was more diffuse than that of insulin immunostaining, and corresponded with the positive staining in the lateral segments of beta-cell plasma membrane, that faced adjacent beta-cells. Glucagon, somatostatin (SRIF) and PP cells stained weakly for GLUT-2, weaker than that of beta-cells. Some nonbeta cells, especially extra-islet PP cells were not stained for GLUT-2. Among islet cell tumors, insulinomas stained less strongly for GLUT-2 than normal beta-cells from the adjacent normal pancreas. Gastrinomas, glucagonomas, and PPomas stained weaker than insulinomas. Even nonfunctioning islet cell tumors were weakly stained for GLUT-2. The positive staining for GLUT-2 observed for islets cells and all islet tumors is consistent with the notion that all pancreatic islet cells and islet cell tumors utilize glucose as a major fuel, requiring transporter-facilitated diffusion of glucose into the cells of normal organ and their tumors.