首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Sato A  Wang PC  Ohgawara H 《Pancreas》2002,25(1):86-93
INTRODUCTION: Transplantation of glucose-responsive insulin-secreting cells has the potential to result in a cure for diabetes. AIM: To report the development of a model of adult porcine pancreatic endocrine cells (PE cells) exhibiting glucose-stimulated insulin secretion during a long-term culture period, in vitro. METHODOLOGY: The PE cells were prepared by non-enzymatic digestion and purified by modifying a technique developed in our laboratory. The cells were first cultured for 7 days in RPMI-1640 medium containing 10% fetal bovine serum and 10 mM nicotinamide. On adhesion to the culture flasks, cells were collected by trypsinization, and then cultured in tissue culture dishes in medium with or without stimulators such as glucagon-like peptide-1 (GLP-1), pituitary adenylate cyclase-activating polypeptide (PACAP), and nicotinamide. The ability of the cells to respond to glucose-stimulated insulin secretion was also observed with and without stimulators. The immunocytochemical studies demonstrated pancreatic islets with well-preserved insulin and glucagon-containing cells. The morphologic integrity of cultured porcine cells was observed for up to 5-6 weeks after the purification. RESULTS: At a concentration of 3.3 mM glucose, PACAP and nicotinamide did not affect glucose-dependent insulin secretion, whereas 10 nM GLP-1 stimulated insulin secretion significantly. However, when glucose concentration was increased to 20 mM, 10 nM GLP-1 had no effect on insulin secretion. We also demonstrated that GLP-1 and PACAP could maintain insulin secretion better than control in the culture up to 5 weeks. Also GLP-1 and PACAP increased the number of insulin-secreting cells in culture. CONCLUSION: These results demonstrate that GLP-1 and PACAP increased the number of pancreatic beta-cells in culture.  相似文献   

2.
《Pancreatology》2003,3(4):342-348
Previously we have demonstrated inhibitory effects of the plant lectin wheat germ agglutinin (WGA) on 125I-CCK-8 binding to pancreatic AR42J cells as well as on CCK-8-stimulated Ca2+ release and α-amylase secretion of rat pancreatic acini or acinar cells. Therefore, it is entirely conceivable that α-amylase having several lectin-like carbohydrate recognition domains can modulate the CCK-8 stimulated lipase secretion. Human α-amylase, purified from pancreatic juice by affinity chroma-tography to homogeneity, and commercial porcine pancreatic α-amylase inhibit CCK-8-stimulated lipase secretion of rat pancreatic acini in a concentration-dependent manner. Acarbose, a specific inhibitor of α-amylase, was without effect on CCK-8-induced cellular lipase secretion. The data presented here provide evidence for a regulatory function of a-amylase in CCK-8-stimulated pancreatic secretion.  相似文献   

3.
Pirenzepine is a newly developed anticholinergic drug that reduces gastric acid secretion and is therefore used in Europe and Japan to treat patients with peptic ulcer. The inhibitory effect of pirenzepine on pancreatic exocrine function and its reversibility were studied in the isolated pancreatic acini and the isolated perfused pancreas of rats. In the isolated acini, pirenzepine caused a concentration-dependent rightward shift in the dose-response curve for carbamylcholine-stimulated amylase secretion without altering the maximal increase. Addition of 10 microM pirenzepine at the beginning as well as after 10 or 20 min of stimulation with 1 microM carbamylcholine rapidly abolished pancreatic secretions in both the isolated acini and isolated perfused pancreas. The inhibitory effect of pirenzepine was fully reversible in the isolated acini, whereas pirenzepine caused a small residual inhibition on pancreatic exocrine secretion in the isolated perfused pancreas. These results suggest the existence of pirenzepine-sensitive receptors in the pancreatic vagal pathway at a site remote from the acinar cell. The present data indicate that pirenzepine may have an influence on pancreatic exocrine function by inhibiting not only acinar cell cholinergic receptor but also endogenous cholinergic activity of the pancreas when a large dose is given.  相似文献   

4.
The existence of negative feedback inhibition of human pancreatic enzyme secretion by proteases is controversially discussed. We have recently demonstrated that jejunal application of porcine pancreatic extracts, in a dose commonly used to treat digestive insufficiency, stimulated rather than inhibited, human pancreatic enzyme secretion. We have now studied the influence of duodenal application of high concentrations of either pure trypsin or porcine pancreatic extracts with trypsin-equivalent activity, on human pancreatic enzyme secretion. Twenty-three male volunteers were intubated with a gastric tube and a two-lumen jejunal tube to collect secretions separately via the first and third tubes and to perfuse either pure trypsin or porcine pancreatic extracts distal to the pylorus via the second tube. PEG-4.000 was continuously perfused via the second tube to correct for losses of volume. Volunteers received PEG alone during the first hour, phenylalanine during the second, PEG alone again during the third, and either phenylalanine together with trypsin or porcine pancreatic extracts during the fourth h. Activities of lipase, amylase, and chymotrypsin were measured in 15-min fractions. In addition, human lipase secretion was measured with an enzyme immunoassay, which does not crossreact with porcine lipase. Plasma cholecystokinin (CCK) was measured using a sensitive bioassay, which utilizes amylase release by isolated rat pancreatic acini. Perfusion of the duodenum with phenylalanine caused a statistically significant stimulation of enzyme secretion. This stimulation could be inhibited by high concentrations of pure trypsin. In contrast, application of porcine pancreatic extracts, which contained the equivalent activity of trypsin, caused further increases of lipase secretion when compared to phenylalanine alone.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
BACKGROUND: Transforming growth factors betas (TGF-betas) are implicated in pancreatic tissue repair but their role in acute pancreatitis is not known. To determine whether endogenous TGF-betas modulate the course of caerulein induced acute pancreatitis, caerulein was administered to wild-type (FVB-/-) and transgenic mice that are heterozygous (FVB+/-) for expression of a dominant negative type II TGF-beta receptor. METHODS: After 7 hourly supramaximal injections of caerulein, the pancreas was evaluated histologically and serum was assayed for amylase and lipase levels. Next, the effects of caerulein on amylase secretion were determined in mouse pancreatic acini, and cholecystokinin (CCK) receptor expression was assessed. RESULTS: The normal mouse pancreas was devoid of inflammatory cells whereas the pancreas from transgenic mice contained lymphocytic infiltrates. Caerulein injection in wild-type mice resulted in 6- and 36-fold increases in serum amylase and lipase levels, respectively, increased serum trypsinogen activation peptide (TAP) levels, gross oedema and a marked inflammatory response in the pancreas that consisted mainly of neutrophils and macrophages. By contrast, FVB+/- mice exhibited minimal alterations in response to caerulein with attenuated neutrophil-macrophage infiltrates. Moreover, acini from FVB+/- mice did not exhibit restricted stimulation at high caerulein concentrations, even though CCK receptor mRNA levels were not decreased. CONCLUSION: Our findings indicate that a functional TGF-beta signalling pathway may be required for caerulein to induce acute pancreatitis and for the CCK receptor to induce acinar cell damage at high ligand concentrations. Our results also support the concept that restricted stimulation at high caerulein concentrations contributes to the ability of caerulein to induce acute pancreatitis.  相似文献   

6.
The pancreatic secretagogue cholecystokinin (CCK) is widely thought to stimulate enzyme secretion by acinar cells indirectly via activation of the vagus nerve. We postulate an alternative pathway for CCK-induced pancreatic secretion. We hypothesize that neurally related pancreatic stellate cells (PSCs; located in close proximity to the basolateral aspect of acinar cells) play a regulatory role in pancreatic secretion by serving as an intermediate target for CCK and secreting the neurotransmitter acetylcholine (ACh), which, in turn, stimulates acinar enzyme secretion. To determine whether PSCs (i) exhibit CCK-dependent ACh secretion and (ii) influence acinar enzyme secretion, primary cultures of human and rat PSCs were used. Immunoblotting and/or immunofluorescence was used to detect choline acetyltransferase (ACh synthesizing enzyme), vesicular ACh transporter (VAChT), synaptophysin, and CCK receptors 1 and 2. Synaptic-like vesicles in PSCs were identified by EM. ACh secretion by PSCs exposed to 20 pM CCK was measured by LC-MS/MS. Amylase secretion by acini [pretreated with and without the muscarinic receptor antagonist atropine (10 μM) and cocultured with PSCs] was measured by colorimetry. PSCs express ACh synthesizing enzyme, VAChT, synaptophysin, and CCK receptors; exhibit CCK-dependent ACh secretion; and stimulate amylase secretion by acini, which is blocked by atropine. In conclusion, PSCs express the essential elements for ACh synthesis and secretion. CCK stimulates ACh secretion by PSCs, which, in turn, induces amylase secretion by acini. Therefore, PSCs may represent a previously unrecognized intrapancreatic pathway regulating CCK-induced pancreatic exocrine secretion.  相似文献   

7.
The acinar cell culture plays a very important role in research of pancreatic pathophysiology. The aim of this study was to establish a long-term culture of human (foetal) pancreatic acinar cells in standardized nutrient media with supplements. Acinar cells were prepared from pancreatic tissues obtained from aborted foetus (> or =35 weeks) with no prior pancreatic complications by collagenase digestion and cultured using different media and supplements. The purity and phenotype of acinar cells was confirmed by various staining techniques and FACS. The acinar cell proliferation was determined at different time intervals by Bromo-deoxyuridine (BrdU) incorporation, and metabolic enzyme activity was analysed. The acini could be cultured and maintained in Ham's F-12 K/M199 media in the presence of 5% BSA, 0.1 mg/ml STI, 10 ng/ml EGF, and 10% FCS with the same morphological appearance as that of freshly prepared for 12 days with maximum viability of 80-85% and formation of monolayer without extracellular matrix. A significant BrdU incorporation of acinar cells in primary culture was observed which was maximum (105%) at day four. Higher amylase and lipase activity was seen in freshly isolated acinar cells which decreased with time of the culture. The established human pancreatic acinar cell culture may act as an excellent model to study exocrine dysfunction or pancreatitis in response to acinar cell injury.  相似文献   

8.
BACKGROUND: Pancreatic production and in vivo effects of nitric oxide (NO) have been shown by several studies. In order to examine the direct actions of the NO donor sodium nitroprusside (SNP), this study used in vitro specimens of the rat pancreas where the distribution of neuronal nitric oxide synthase (NOS) and the secretory effects of SNP and the cyclic GMP (cGMP) analog 8-bromo cyclic GMP (8-Br cGMP) were investigated. METHODS: NO containing pancreatic nerves were visualized by NOS immunohistochemistry. Basal and stimulated amylase output from rat pancreatic segments was measured by an on-line fluorimetric method. Stimulation was achieved by either acetylcholine (ACh) or electrical field stimulation (EFS). Intracellular free calcium concentration ([Ca2+]i) was measured in dispersed pancreatic acinar cells. RESULTS: NOS containing nerves were demonstrated in the vicinity of pancreatic acini and blood vessels. SNP and 8-Br cGMP inhibited both basal and EFS evoked amylase output but failed to inhibit ACh induced amylase output. Basal [Ca2+]i was decreased by both SNP and 8-Br cGMP but neither SNP nor 8-Br cGMP influenced the ACh evoked increase in [Ca2+]i. CONCLUSION: NO is well distributed in the rat exocrine pancreas. Exogenous nitric oxide may have a dual action in the isolated rat pancreas: Inhibition of basal amylase secretion in acinar cells and inhibition of ACh release from intrinsic nerve terminals. Both effects seem to be calcium dependent and possibly mediated by cGMP.  相似文献   

9.
Gap junctional coupling modulates secretion of exocrine pancreas.   总被引:4,自引:0,他引:4       下载免费PDF全文
Dispersed pancreatic acini were studied to assess the function of junctional coupling between adult secretory cells. Nonstimulated control cells were extensively coupled to their neighbors throughout each acinus. Addition of heptanol caused their uncoupling and increased their basal amylase release. Neurotensin, secretin, and vasoactive intestinal peptide (VIP) stimulated amylase secretion without uncoupling acinar cells. Heptanol rapidly and markedly uncoupled the neurotensin-, secretin-, and VIP-stimulated acinar cells and increased their amylase secretion in an additive manner. By contrast, the secretory response to carbamoylcholine (carbachol), a secretagogue that, alone, uncoupled acinar cells, was not affected by heptanol. Basal as well as neurotensin-, secretin-, and VIP-stimulated output returned to the lower control values following removal of heptanol and recovery of normal coupling. The data provide evidence that blockage of gap junctional coupling increases the basal secretion of exocrine pancreas as well as the response of the gland to a variety of secretagogues.  相似文献   

10.
Pancreatic enzyme secretion is inhibited during acute pancreatitis, resulting in an increase in acinar zymogen content. Since the premature activation of zymogens has been assigned a central role in the pathogenesis of acute pancreatitis, minimizing the amount of stored zymogens might lead to less severe acute pancreatitis. Inhibition of enzyme synthesis or stimulation of enzyme secretion would result in reduction of zymogen stores. Opiates have a varying effect on pancreatic secretion, depending on the dosage, site of administration, and presence of pancreatic stimulants. The effect of opiates and acute pancreatitis on individual pancreatic enzyme synthesis is unknown. The following study was undertaken in order to examine the effects of an opiate on pancreatic enzyme secretion and synthesis during experimental acute pancreatitis. Four groups of rats were studied. Group I received cerulein (25 µg/kg); group II received an opiate, buprenorphine (BPN, 0.5 mg/kg); and group III received cerulein and BPN. Drugs were dissolved in gelatin/saline and injected subcutaneously. A control group (group IV) received only gelatin/saline. Rats were sacrificed 4 hr after injection, and pancreatic mass was measured. Pancreatic acini were prepared and assayed for amylase and DNA content. Amylase, trypsinogen, chymotrypsinogen and lipase synthesis, and amylase secretion were measured for 2 hr. Results showed that, compared to controls, acini of rats with AP had increased amylase content, a finding consistent with decreasedin vivo amylase secretion. Total protein and individual enzyme synthesis rates were significantly lower in the acini of the rats with AP than in those of the controls. Negative feedback inhibition of enzyme synthesis due to the increased stores of intracellular enzymes may account for these findings. BPN reduced pancreatic edema in rats with acute pancreatitis (AP). Acinar amylase content of rats with AP treated with BPN was significantly lower than in acini of rats with AP. As amylase secretion was lower in the AP + BPN rats, the reduced acinar amylase content was probably solely due to the reduction in enzyme synthesis observed in the AP + BPN rats. The results suggest that BPN may have a moderating effect on the development of AP.This study was supported by a research grant from the South African Medical Research Council.  相似文献   

11.
This study was designed to determine the distribution of immunoreactive epidermal growth factor (EGF) in the gastrointestinal tract and the action of this peptide on pancreatic secretion in vivo and in vitro. Immunoreactive EGF was found in large amounts in the salivary glands and the pancreas and in the pancreatic juice. EGF infused subcutaneously (50 micrograms/kg-h) in conscious rats with intact or removed salivary glands stimulated pancreatic protein secretion after 4 h of peptide infusion; this effect was completely prevented by the pretreatment with DL-difluoromethyl-ornithine (DFMO) (200 mg/kg), an irreversible inhibitor of activity of ornithine decarboxylase (ODC), a key enzyme in polyamine synthesis. EGF added to the incubation medium in concentrations ranging from 10(-10)-10(-6) M increased, in a concentration-dependent manner both unstimulated and stimulated by caeruelin or urecholine, amylase release from dispersed pancreatic acini obtained from rats pretreated in 3 h with EGF in a dose of 50 micrograms/kg-h. Spermine given at concentrations ranging from 10(-12)-10(-6) M to the freshly prepared rat pancreatic acini also increased amylase release in a concentration-related manner. DFMO injected in a single dose (200 mg/kg), before the infusion of EGF to the rats, completely abolished the stimulatory effect of EGF on amylase release, but failed to affect that of spermine. This study shows that 1. EGF is present in large amounts in pancreatic tissue and pancreatic juice. 2. EGF stimulates pancreatic secretion in vivo and amylase release in vitro from isolated rat pancreatic acini. 3. The activation of ODC and polyamine biosynthesis in acinar cells plays an important role in EGF-induced stimulation of pancreatic secretion.  相似文献   

12.
The effects of proglumide analogue. CR 1392, on pancreatic exocrine secretion were studied in the isolated pancreatic acini and the isolated perfused pancreata of rats. In the isolated acini, CR 1392 caused a parallel rightward shift of the dose-response curve for amylase secretion stimulated by cholecystokinin octapeptide (CCK-8). CR 1392 inhibited maximally stimulated amylase release by CCK-8 (100 pM) in a concentration-dependent manner, with a half maximal inhibition (ID50) at 8.0 +/- 0.6 microM. CR 1409, another proglumide analogue, also caused a concentration-dependent inhibition (ID50: 3.2 +/- 0.4 microM). Although CR 1409 was about 2.5-fold more potent than CR 1392 in inhibiting the stimulated amylase release, 1 mM CR 1409 caused 107.4 +/- 0.9% increase in amylase release, suggesting acinar cell damage. CR 1392 (1 mM) also caused 19.9 +/- 2.3% increase in amylase release, but was less toxic than CR 1409. The antagonism produced by CR 1392 was selective for CCK and had no effect on amylase release stimulated by other receptor secretagogues or by agents bypassing receptors. CR 1392 added 20 min after the CCK-8 stimulation rapidly abolished pancreatic exocrine secretion in both isolated acini and isolated perfused pancreas. Although the inhibitory effect of CR 1392 was fully reversible in the isolated acini, the pancreata perfused with 100 microM CR 1392 for 20 min did not respond to the subsequent stimulation with CCK-8 for more than 20 min. These results indicate that CR 1392 is a potent, competitive, specific and long acting antagonist of CCK in rat pancreas.  相似文献   

13.
BACKGROUND: We recently demonstrated that chronic physical exercise increases pancreatic protein content and basal amylase secretion. It is unknown whether chronic exercise causes hypertrophy or proliferation of pancreatic acinar cells. METHODS: Female F344 rats (age, 6 wk) were divided into control (n = 7) and exercise (n = 6) groups. Food consumption was matched between the 2 groups. Rats in the control group were kept sedentary. Rats in the exercise group were exercised for 60 min, 5 d/wk during the experiment. After 8 wk, the pancreas and hindlimb muscles were rapidly excised and weighed. Protein and DNA content and enzyme activity in pancreatic tissue were measured. Pancreatic tissues from control and exercised rats were also prepared for transmission electron microscopy. RESULTS: Inhibition of growth and hypertrophy of hindlimb muscles were exhibited by the exercise group. In the exercise group, pancreatic wet weight, protein content, and amylase and lipase activities, but not DNA content, were significantly higher than those in the control group. Electron micrographs clearly revealed that acinar cells were hypertrophied and zymogen granules were increased in number in exercised rats. CONCLUSION: Chronic endurance exercise increases pancreatic weight, protein content and enzyme activity through hypertrophy of acinar cells.  相似文献   

14.
Intrapancreatic activation of proteases is believed to play a major role in the pathogenesis of acute necrotizing pancreatitis. Several authors have questioned, however, the central role of trypsin in autodigestion of the pancreas. To clarify the direct effects of pancreatic enzymes and other related factors on acinar cells, we used the model of isolated pancreatic acini. Acini were prepared from male Wistar rats by collagenase digestion. Protein synthesis was measured by incubation of acini with [35S]methionine. Acini were resuspended thereafter in fresh buffer and further incubated for 30-90 min under various conditions [e.g., with pancreatic homogenates, ascites (from rats with pancreatitis induced by sodium taurocholate), pure pancreatic enzymes, and other factors]. The percentage of release of newly synthesized proteins into the culture medium was regarded as a biochemical parameter of cellular integrity. A morphologic score of cellular integrity was obtained via light microscopic evaluation of acini at the end of the various incubations by measuring the degree of cell lysis, loss of cell granules, ballooning, formation of vacuoles, and karyopyknosis. When normal [35S]methionine-labeled pancreatic acini were incubated with various factors, the percentage of release of labeled proteins into the medium was as follows: incubation with HEPES/Ringer's buffer, 1.8%; hemorrhagic pancreatic ascites, 3.8%; pancreatic homogenates, 2.0%; lipase, 1.8%; phospholipase A2, 3.0%; phospholipase A2 + lecithin, 3.2%; trypsin, 2.5%; 5% olive oil, 1.8%; ascites + olive oil, 78.3%; ascites + homogenized epididymal fat, 79.9%; lipase + olive oil, 32.0%; pancreatic homogenates + olive oil, 28.0%; diolein, 2.65%; and oleic acid, 62.9%. The cellular release of radiolabeled proteins showed an inverse correlation with cellular integrity as shown by light microscopy. We postulate that interstitial release of degradation products from triglycerides by lipase causes cellular disruption. Whereas phospholipase A2 and proteases do not seem to be very harmful in the early phases of cellular damage, lipase may play a major role in acute necrotizing pancreatitis.  相似文献   

15.
INTRODUCTION: Numerous studies have been carried out on the agonist-evoked calcium responses of single pancreatic acinar cells; however, several reports have shown that dissociation of the exocrine pancreas into predominantly single cells has an adverse effect on agonist-evoked amylase secretion. AIMS AND METHODOLOGY: To determine whether single acinar cells behave in an anomalous manner compared with cells within an intact acinus, we measured exocytosis in both single acinar cells and acini (2-5 cells) present in the same preparation. Exocytosis of individual zymogen granules was quantified in real-time by using the technique of continuous time-differential analysis of brightfield digital images. RESULTS: Basal rates of exocytosis were low in both single cells and intact acini. Application of 10 microM acetylcholine for 6 minutes stimulated a biphasic secretory response in acinar cells. Additionally, we found that exocytotic events occur repetitively in specific locations within the apical domain; i.e., there are exocytotic "hot spots." There were no statistically significant differences between the exocytotic rates, nor were there any differences in the characteristics of the exocytotic hot spots of single cells compared with those of acini. CONCLUSION: We conclude that time-differential analysis of brightfield images appears to be a useful tool for the investigation of the role of gap junctions in zymogen granule exocytosis and that single acinar cells provide a reasonable model for studies of acinar cell signaling and secretion.  相似文献   

16.
The acute and chronic effects of hydrocortisone on exocrine pancreatic function were examined in the isolated perfused rat pancreas. In the first part of this study, rats were given subcutaneous injections of hydrocortisone at doses of 1.25, 2.5, 5, and 10 mg/kg body wt once daily for 7 days. Trypsin and lipase secretion in response to 100 pM cholecystokinin-octapeptide was significantly increased in rats with the two highest doses of hydrocortisone compared with controls, irrespective of whether calculated as the total amount of stimulated output of enzymes or related to the secretion of enzyme to the pancreas content. On the other hand, the secretory responsiveness of amylase to 100 pM cholecystokinin-octapeptide was maximal at the 5-mg dose, and decreased with higher doses. In the second part, 100 microM hydrocortisone was superimposed for 20 min on 100 pM cholecystokinin-octapeptide stimulation to examine the acute effects of hydrocortisone on exocrine pancreatic function in the isolated perfused rat pancreas. Addition of hydrocortisone caused a significant inhibition of the secretion of pancreatic juice and amylase. The present study has clearly demonstrated the dual effects of glucocorticoids on the pancreas: inhibition and potentiation. There is a possibility that chronic treatment with large doses of glucocorticoid may sensitize the acinar cells an induce hypersecretion of trypsin and lipase, whereas acute treatment inhibits secretory function of exocrine pancreas.  相似文献   

17.
Activity of the insulo-acinar axis in the isolated perfused rat pancreas   总被引:2,自引:0,他引:2  
The object of the present investigation was to determine whether insulin secreted by the endocrine pancreas and carried in the insulo-acinar portal system has a direct effect on pancreatic enzyme secretion. For this purpose, the isolated rat pancreas was perfused in a nonrecirculating system. The perfusate contained 3 mM glucose, and either caerulein or vaso-active intestinal polypeptide was used to stimulate exocrine secretion. The amount of insulin reaching the exocrine pancreas was reduced by two different experimental procedures. In the first, use was made of streptozotocin-diabetic rats treated with insulin in vivo. Treatment was such that the contents of amylase and lipase, vastly altered in the untreated diabetic state, were normalized before the perfusion studies. In the second procedure, insulin reaching the exocrine pancreas was reduced by antiinsulin serum in the perfusate. In these procedures, the reduced insulin bioavailability was associated with a reduction in caerulein- and vasoactive intestinal polypeptide-stimulated enzyme release, which was shown as a reduction of maximum responsiveness to caerulein without alteration of sensitivity. By contrast, in dispersed pancreatic acini where the insulo-acinar axis was completely disrupted, amylase secretion from diabetic and nondiabetic tissue was identical over a wide range of caerulein concentrations, showing that the secretory defect seen in the perfusion studies was not inherent to the exocrine tissue. The results show that basal insulin secretion has a direct effect on pancreatic enzyme output and that the insulo-acinar axis may play an important role in the regulation of acinar cell function.  相似文献   

18.
Although several studies have suggested that insulin-secreting cells can be generated in vitro from cells residing in adult exocrine pancreas, neither the origin of these cells nor their precise insulin secretory properties was obtained. We show here that insulin-secreting cells can be derived from adult mouse pancreatic exocrine cells by suspension culture in the presence of EGF and nicotinamide. The frequency of insulin-positive cells was only 0.01% in the initial preparation and increased to approximately 5% in the culture conditions. Analysis by the Cre/loxP-based direct cell lineage tracing system indicates that these newly made cells originate from amylase/elastase-expressing pancreatic acinar cells. Insulin secretion is stimulated by glucose, sulfonylurea, and carbachol, and potentiation by glucagon-like peptide-1 also occurs. Insulin-containing secretory granules are present in these cells. In addition, we found that the enzymatic dissociation of pancreatic acini itself leads to activation of EGF signaling, and that inhibition of EGF receptor kinase blocks the transdifferentiation. These data demonstrate that pancreatic acinar cells can transdifferentiate into insulin-secreting cells with secretory properties similar to those of native pancreatic beta cells, and that activation of EGF signaling is required in such transdifferentiation.  相似文献   

19.
We examined the inhibitory effect of L-364,718, a nonpeptide cholecystokinin (CCK) antagonist, on CCK stimulation of pancreatic exocrine and endocrine secretion in both the isolated pancreatic acini and the isolated perfused pancreata of rats. In the isolated acini, L-364,718 inhibited CCK octapeptide (CCK-8)-stimulated amylase release and binding of 125I-CCK-8 in a dose-dependent manner without appreciable effects on the basal amylase secretion. L-364,718 also inhibited amylase release in response to caerulein and gastrin I, but had no effect on amylase release stimulated by other secretagogues or by agents bypassing receptors. Similarly, binding of N-methylscopolamine to pancreatic acini was not inhibited by L-364,718. In the isolated perfused pancreata, L-364,718 inhibited CCK-8-stimulated pancreatic exocrine secretion and insulin release. The inhibitory effects of L-364,718 were more potent for insulin release than for exocrine secretion and persisted even after the removal of L-364,718 infusion. These results clearly demonstrate that L-364,718 is a specific, potent, and prolonged antagonist of CCK's stimulatory actions on pancreatic acinar and B cells.  相似文献   

20.
To investigate the role of calmodulin in stimulus-secretion coupling in pancreatic acinar cells, we studied the effects of W-7, a calmodulin inhibitor, and KN-62, a specific inhibitor of Ca2+/calmodulin-dependent protein kinase II (Ca2+/CaM kinase II), on amylase secretion from rat pancreatic acini. Calmodulin inhibitor (W-7, 100 microM) and Ca2+/CaM kinase II inhibitor (KN-62, 10 microM) reduced amylase secretion stimulated by cholecystokinin (CCK) or carbachol. W-7 and KN-62 also inhibited amylase secretion stimulated by both calcium ionophore (A23187) and phorbol ester (12-O-tetradecanoylphorbol-13-acetate, TPA). To clarify the role of calmodulin in the interaction of intracellular mediators, pancreatic acini were permeabilized with streptolysin O. Following permeabilization, amylase secretion was stimulated by submicromolar free Ca2+, and this Ca(2+)-dependent amylase secretion was enhanced by guanosine 5'-[gamma-thio]triphosphate (GTP gamma S), TPA or cyclic adenosine 3',5'-monophosphate (cAMP). W-7 and KN-62 had no effects on amylase secretion stimulated by Ca2+ alone, but inhibited the enhancement in Ca(2+)-dependent amylase secretion by GTP gamma S, TPA or cAMP. These data suggest that calmodulin plays an important role in Ca(2+)-dependent amylase secretion from pancreatic acinar cells and in the interaction between Ca2+ and other intracellular messengers.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号