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All cells in the body are exposed to physical force in the form of tension, compression, gravity, shear stress, or pressure. Cells convert these mechanical cues into intracellular biochemical signals; this process is an inherent property of all cells and is essential for numerous cellular functions. A cell's ability to respond to force largely depends on the array of mechanical ion channels expressed on the cell surface. Altered mechanosensing impairs conscious senses, such as touch and hearing, and unconscious senses, like blood pressure regulation and gastrointestinal (GI) activity. The GI tract's ability to sense pressure changes and mechanical force is essential for regulating motility, but it also underlies pain originating in the GI tract. Recent identification of the mechanically activated ion channels Piezo1 and Piezo2 in the gut and the effects of abnormal ion channel regulation on cellular function indicate that these channels may play a pathogenic role in disease. Here, we discuss our current understanding of mechanically activated Piezo channels in the pathogenesis of pancreatic and GI diseases, including pancreatitis, diabetes mellitus, irritable bowel syndrome, GI tumors, and inflammatory bowel disease. We also describe how Piezo channels could be important targets for treating GI diseases., Introduction Mechanotransduction is essential for sensing touch, hearing, and autonomic functions such as blood pressure regulation, gastrointestinal (GI) motility, cell differentiation and development, muscle stretch, and vascular tone (1, 2). [...]

Visceral pain associated with irritable bowel syndrome afflicts 15% of the US population. Although treatments are limited, guanylyl cyclase C (GUCY2C) agonists alleviate pain and constipation. Until now, it was assumed that the activation of GUCY2C and production of cGMP in enterocytes stimulated fluid secretion and reduced visceral sensation. The recent discovery that a subtype of enteroendocrine cells (EECs) known as neuropod cells synapse with submucosal neurons unveiled a pathway for communicating gut signals to the nervous system. In this issue of the JCI, Barton et al. report that GUCY2C is enriched in neuropod cells and is involved with sensory nerve firing. Selective deletion of GUCY2C in mouse models suggests that defective GUCY2C neuropod-cell signaling underlies visceral pain. These studies introduce possibilities for dissociating the secretory and analgesic effects of GUCY2C agonism. Although further work remains, unveiling the role of neuropod cells is a major step in understanding visceral pain., Unexplained visceral pain It has been estimated that up to 50% of visits to a gastroenterologist are for evaluation and treatment of unexplained visceral pain, commonly referred to as irritable [...]

Elevated pressure in the pancreatic gland is the central cause of pancreatitis following abdominal trauma, surgery, endoscopic retrograde cholangiopancreatography, and gallstones. In the pancreas, excessive intracellular calcium causes mitochondrial dysfunction, premature zymogen activation, and necrosis, ultimately leading to pancreatitis. Although stimulation of the mechanically activated, calcium-permeable ion channel Piezo1 in the pancreatic acinar cell is the initial step in pressure-induced pancreatitis, activation of Piezo1 produces only transient elevation in intracellular calcium that is insufficient to cause pancreatitis. Therefore, how pressure produces a prolonged calcium elevation necessary to induce pancreatitis is unknown. We demonstrate that Piezo1 activation in pancreatic acinar cells caused a prolonged elevation in intracellular calcium levels, mitochondrial depolarization, intracellular trypsin activation, and cell death. Notably, these effects were dependent on the degree and duration of force applied to the cell. Low or transient force was insufficient to activate these pathological changes, whereas higher and prolonged application of force triggered sustained elevation in intracellular calcium, leading to enzyme activation and cell death. All of these pathological events were rescued in acinar cells treated with a Piezo1 antagonist and in acinar cells from mice with genetic deletion of Piezo1. We discovered that Piezo1 stimulation triggered transient receptor potential vanilloid subfamily 4 (TRPV4) channel opening, which was responsible for the sustained elevation in intracellular calcium that caused intracellular organelle dysfunction. Moreover, TRPV4 gene-KO mice were protected from Piezo1 agonist- and pressure-induced pancreatitis. These studies unveil a calcium signaling pathway in which a Piezo1-induced TRPV4 channel opening causes pancreatitis., Introduction The pancreas is highly sensitive to pressure (1-3), and elevated pancreatic duct pressure is a major cause of acute pancreatitis. A gallstone impacted at the junction of the pancreatic [...]

Due to progressive inflammation, chronic pancreatitis destroys both the exocrine and endocrine pancreas and sensitizes pancreatic nerves, leading to unremitting pain. Unfortunately, there are no treatments for pancreatic inflammation and approaches to ameliorate pain are suboptimal. Pancreatic inflammation is particularly problematic because damage to acinar cells causes local release of digestive enzymes, which initiate pancreatic autodigestion. The combination of autodigestion and inflammation is unique to pancreatitis and undoubtedly contributes to the difficulty in devising effective treatments. In this issue of the JCI, Saleh et al. describe a nonsurgical technique to ablate pancreatic acinar cells, thus eliminating the source of digestive enzymes and preventing autodigestion. In mice and a nonhuman primate model, this approach effectively reduced inflammation and pain while preserving islet cell function. These findings support the concept that ongoing acinar cell damage is at the root of chronic pancreatitis and provide a possible strategy for clinical treatment., Chronic pancreatitis Picture yourself in a hospital room where your son has been admitted with pancreatitis. This is his third attack, and he is only 11 years old. You should [...]

Satiety and other core physiological functions are modulated by sensory signals arising from the surface of the gut. Luminal nutrients and bacteria stimulate epithelial biosensors called enteroendocrine cells. Despite being electrically excitable, enteroendocrine cells are generally thought to communicate indirectly with nerves through hormone secretion and not through direct cell-nerve contact. However, we recently uncovered in intestinal enteroendocrine cells a cytoplasmic process that we named neuropod. Here, we determined that neuropods provide a direct connection between enteroendocrine cells and neurons innervating the small intestine and colon. Using cell-specific transgenic mice to study neural circuits, we found that enteroendocrine cells have the necessary elements for neurotransmission, including expression of genes that encode pre-, post-, and transsynaptic proteins. This neuroepithelial circuit was reconstituted in vitro by coculturing single enteroendocrine cells with sensory neurons. We used a monosynaptic rabies virus to define the circuit's functional connectivity in vivo and determined that delivery of this neurotropic virus into the colon lumen resulted in the infection of mucosal nerves through enteroendocrine cells. This neuroepithelial circuit can serve as both a sensory conduit for food and gut microbes to interact with the nervous system and a portal for viruses to enter the enteric and central nervous systems., Introduction Satiety, food preference, and even mood behaviors are a few of the functions modulated by gut chemosensation (1). Ingested nutrients and bacterial by-products contacting the gut epithelium stimulate enteroendocrine [...]

Cholecystokinin (CCK) is a satiety hormone produced by discrete enteroendocrine cells scattered among absorptive cells of the small intestine. CCK is released into blood following a meal; however, the mechanisms [...]

Endogenous trypsin inhibitors are synthesized, stored, and secreted by pancreatic acinar cells. It is believed that they play a protective role in the pancreas by inhibiting trypsin within the cell should trypsinogen become prematurely activated. Rodent trypsin inhibitors are highly homologous to human serine protease inhibitor Kazal-type 1 (SPINK1). The mouse has one pancreatic trypsin inhibitor known as SPINK3, and the rat has two trypsin inhibitors commonly known as pancreatic secretory trypsin inhibitors I and II (PSTI-I and -II). Rat PSTI-I is a 61-amino acid protein that shares 65% sequence identity with mouse SPINK3. It was recently demonstrated that mice with genetic deletion of the Spink3 gene ([Spink3.sup.-/-]) do not survive beyond 15 days and lack normal pancreata because of pancreatic autophagy. We have shown that targeted transgenic expression of the rat Psti1 gene to acinar cells in mice [TgN(Psti1)] protects mice against caerulein-induced pancreatitis. To determine whether the autophagic phenotype and lethality in [Spink3.sup.-/-] mice were due to lack of pancreatic trypsin inhibitor, we conducted breeding studies with [Spink.sup.3+/-] heterozygous mice and TgN(Psti1) mice. We observed that, whereas [Spink3.sup.+/+], [Spink3.sup.+/-], and [Spink3-/-]/TgN(Pstil) mice had similar survival rates, no [Spink3.sup.-/-] mice survived longer than 1 wk. The level of expression of SPINK3 protein in acini was reduced in heterozygote mice compared with wild-type mice. Furthermore, endogenous trypsin inhibitor capacity was reduced in the pancreas of heterozygote mice compared with wild-type or knockout mice rescued with the rat Psti1 gene. Surprisingly, the lesser amount of SPINK3 present in the pancreata of heterozygote mice did not predispose animals to increased susceptibility to caerulein-induced acute pancreatitis. We propose that a threshold level of expression is sufficient to protect against pancreatitis. doi: 10.1152/ajpgi.00431.2009 PSTI-I; pancreatitis; autophagy

The enteric nervous system has been studied thus far as an isolated unit. As researchers probe deeper into the function of this system, it is evident that the neural network stretches beyond enteric neurons. It is formed by both intrinsic and extrinsic neurons innervating the gut, enteric glia, and innervated sensory epithelial cells, such as enteroendocrine cells. This Review series summarizes recent knowledge on function and disease of nerves, glia, and sensory epithelial cells of the gut in eight distinctive articles. The timing and growing knowledge for each individual field calls for an appropriate term encompassing the entire system. We call this neuronal ensemble the 'gut connectome' and summarize the work from a food sensory perspective., 'Tell me what you eat, and I will tell you what you are,' wrote the French gastronome Jean Brillat-Savarin in 1826 (1). Although at the time of Brillat-Savarin the connection [...]

Primary sensory neurons of the C and A[delta] subtypes express the vanilloid capsaicin receptor TRPV1 and contain proinflammatory peptides such as substance P (SP) that mediate neurogenic inflammation. Pancreatic injury stimulates these neurons causing the release of SP in the pancreas resulting in pancreatic edema and neutrophil infiltration that contributes to pancreatitis. Axons of primary sensory neurons innervating the pancreas course through the celiac ganglion. We hypothesized that disruption of the celiac ganglion by surgical excision or inhibition of C and A[delta] fibers through blockade of TRPV1 would reduce the severity of experimental pancreatitis by inhibiting neurogenic inflammation. Resiniferatoxin (RTX) is a specific TRPV1 agonist that, in high doses, selectively destroys C and A[delta] fibers. Sprague-Dawley rats underwent surgical ganglionectomy or application of 10 [micro]g RTX (vs. vehicle alone) to the celiac ganglion. One week later, pancreatitis was induced by six hourly intraperitoneal injections of caerulein (50 [micro]g/kg). The severity of pancreatitis was assessed by serum amylase, pancreatic edema, and pancreatic myeloperoxidase (MPO) activity. SP receptor (neurokinin-1 receptor, NK-1R) internalization in acinar cells, used as an index of endogenous SP release, was assessed by immunocytochemical quantification of NK-1R endocytosis. Caerulein administration caused significant increases in pancreatic edema, serum amylase, MPO activity, and NK-1R internalization. RTX treatment and ganglionectomy significantly reduced pancreatic edema by 46% (P < 0.001) and NK-1R internalization by 80% and 51% (P < 0.001 and P < 0.05, respectively). RTX administration also significantly reduced MPO activity by 47% (P < 0.05). Neither treatment affected serum amylase, consistent with a direct effect of caerulein. These results demonstrate that disruption of or local application of RTX to the celiac ganglion inhibits SP release in the pancreas and reduces the severity of acute secretagogue-induced pancreatitis. It is possible that selectively disrupting TRPV1-bearing neurons could be used to reduce pancreatitis severity. TRPV1; endocytosis; resiniferatoxin; neurogenic inflammation; neurokinin-1 receptor

Nonsulfated CC[K.sub.58] [CC[K.sub.58](ns)] has not been considered to be of biological importance because CC[K.sub.58](ns) binds poorly to the CC[K.sub.A] receptor and has only been identified once in intestinal extracts. In this work, a radioimmunoassay specific for the COOH-terminal region of gastrin and CCK (antibody 5135) was used to monitor the purification of CCK molecular forms from canine intestinal extracts. A minor immunoreactive peak was associated with a major absorbance peak during an ion-exchange, HPLC step. Characterization of this minor immunoreactive peak demonstrated that it was CC[K.sub.58](ns). CC[K.sub.58](ns) is 14% as immunoreactive as sulfated CC[K.sub.8] [CC[K.sub.8](s)]. Amino acid analysis demonstrated that CC[K.sub.58](ns) was present at 50% the amount of CC[K.sub.58](s). In addition, we found that CC[K.sub.58](ns) does not potently displace an [sup.125]I-labeled CC[K.sub.10] analog from the CC[K.sub.A] receptor in mouse pancreatic membranes and does not stimulate amylase release from isolated pancreatic acini, or stimulate pancreatic secretion in an anesthetized rat model. By contrast, CC[K.sub.58](ns) does bind to CC[K.sub.B] receptors and stimulates gastric acid secretion via this receptor. The presence of CC[K.sub.58](ns) and its ability to selectively stimulate the CC[K.sub.B] receptor without stimulation of the CC[K.sub.A] receptor suggest that CC[K.sub.58](ns) may have unique physiological properties, especially tissues where the nonsultated peptide can act as a paracrine or neurocrine agent. gallbladder: pancreas; gastric acid; receptor binding; CC[K.sub.A]; CC[K.sub.B]

CCK acts on pancreatic acinar cells to increase intracellular [Ca.sup.2+] leading to secretion of digestive enzymes and, in the long term, pancreatic growth. Calcineurin (CN) is a serine/ threonine-specific protein phosphatase activated by [Ca.sup.2+] and calmodulin that recently has been shown to participate in the growth regulation of cardiac and skeletal myocytes. We therefore tested the effect of two different CN inhibitors, cyclosporine A (CsA) and FK506, on mouse pancreatic growth induced by oral administration of the synthetic protease inhibitor camostat, a known stimulator of endogenous CCK release. Mice were fed a powdered diet with or without 0.1% camostat. Pancreatic wet weight, protein, and DNA were increased in response to camostat in a time-dependent manner over 10 days in ICR mice but not in CCK-deficient mice. Both CsA (15 mg/kg) and FK506 (3 mg/kg) given twice daily blocked the increase in pancreatic wet weight and protein and DNA content induced by camostat. The increase in plasma CCK induced by camostat was not blocked by CsA or FK506. Camostat feeding also increased the relative amount of CN protein, whereas levels of MAPKs, ERKs, and p38 were not altered. In summary, 1) CCK released by chronic camostat feeding induces pancreatic growth in mice; 2) this growth is blocked by treatment with both CsA and FK506, indicating a role for CN; 3) CCK stimulation also increases CN protein. In conclusion, activation and possibly upregulation of CN may participate in regulation of pancreatic growth by CCK in mice. cholecystokinin; camostat; FK506; cyclosporine A

We hypothesized that neurogenic inflammation is a common final pathway for parenchymal inflammation in pancreatitis and evaluated the role of primary sensory neurons in secretagogue-induced and obstructive pancreatitis. Neonatal rats received either the primary sensory neuron-denervating agent capsaicin (50 mg/kg sc) or vehicle. At 8 wk of age, pancreatitis was produced by six hourly injections of caerulein (50 [micro]g/kg ip) or by common pancreaticobiliary duct ligation (CPBDL). The severity of pancreatitis was assessed by serum amylase, pancreatic myeloperoxidase (MPO) activity, histological grading, pancreatic plasma extravasation, and wet-to-dry weight ratio. Caerulein significantly increased MPO activity and wet-to-dry weight ratio, produced histological evidence of edematous pancreatitis, induced plasma extravasation, and caused hyperamylasemia. CPBDL increased MPO activity and produced histological evidence of pancreatitis. Neonatal capsaicin administration significantly reduced tissue MPO levels, histological severity scores, and wet-to-dry weight ratio and abolished plasma extravasation. These results demonstrate that primary sensory neurons play a significant role in the inflammatory cascade in experimental pancreatitis and appear to constitute a common final pathway for pancreatic parenchymal inflammation. caerulein; capsaicin; common pancreaticobiliary duct ligation; neurogenic inflammation; substance P

Luminal CCK-releasing factor stimulates CCK release from human intestinal endocrine and STC-1 cells. Am J Physiol Gastrointest Liver Physiol 282: G16-G22, 2002.--CCK is secreted into the blood from intestinal endocrine cells following ingestion of a meal. Recently, it has been demonstrated that the ability of certain foods to stimulate CCK release is mediated by endogenously produced CCK-releasing factors. A newly discovered luminal CCK-releasing factor (LCRF) is secreted into the intestine, where it stimulates CCK secretion. However, the mechanism whereby LCRF affects intestinal epithelial cells is unknown. The current study was designed to determine whether LCRF has a direct effect on CCK cells to stimulate hormone secretion. In dispersed human intestinal mucosal cells, LCRF (5-200 nM) significantly stimulated CCK release in a concentration-dependent manner. This stimulatory effect was absent in calcium-free media and was inhibited by the L-type calcium-channel blockers diltiazem and nifedipine. To examine direct cellular effects of LCRF on CCK cells, further studies were conducted in the CCK-containing enteroendocrine cell line STC-1. As in native cells, LCRF significantly stimulated CCK release from STC-1 cells in a calcium-dependent manner. In cells loaded with a calcium-sensitive dye, LCRF stimulation produced a rapid increase in intracellular calcium. To examine the electrophysiological basis for this stimulation, whole cell recordings were made from STC-1 cells. Whole cell calcium currents were identified under basal conditions; moreover, calcium-channel activity was increased by LCRF. These studies demonstrate that 1) LCRF has a direct effect on human intestinal cells to stimulate CCK secretion, 2) stimulated hormone release is calcium dependent, and 3) LCRF activates calcium currents in CCK cells, which leads to CCK secretion. cholecystokinin; secretion; gastrointestinal hormone; calcium; ion channel; fluorescence

The role of electroneutral Na+/H+ exchange (NHE) in extracellular acidification and hormone secretion was investigated. Results indicated that stimulation of cholecystokinin (CCK) secretion is functionally linked with activation of NHE through a mechanism that may involve pH-sensitive changes in membrane potential. It was proposed that inhibition of NHE lowers intracellular pH and causes membrane depolarization through the effects of H+ on K+ permeability.

The effect of chylomicron formation on signal transduction that promotes gastric emptying is investigated in awake rats using an inhibitor of chylomicron formation. Results reveal that inhibition of chylomicron formation reversed the inhibition of gastric emptying brought about by intraluminal lipids. This indicates that chylomicron formation is an important component in the signaling system of cholecytokinin secreting cells in the intestinal mucosa.

The role of adenosine triphosphate (ATP) as a signaling factor that regulates bile duct secretion through apical purinergic receptors in cholangiocytes was investigated. A novel healthy rat cholangiocyte was used in an experiment to determine the basal properties of cholangiocyte monolayers, the pharmacological properties of apical receptors and the conductances attenuating the short-circuit current. Results showed that nucleotides stimulated transepithelial transport through receptor activation in the apical membrane.

The biological mechanism of action of the luminal cholecystokinin (CCK)-releasing factor (LCRF)-(1-35) was investigated. Adult male Wistar rats were used as experimental models to determine the dose-response relationships of protein and fluid secretion following the administration of synthetic LCRF fragments. Results indicated that LCRF-(1-35) is similar to the natural peptide in terms of biological activity on CCK release and pancreatic secretion. LCRF-(1-35) also increased plasma CCK to significant levels while pancreatic secretory response to the peptide was eliminated.

Nitric oxide acts as an important regulator of cholecystokinin (CCK) release in the gastrointestinal tract. NO activates the potassium channels that promote CCK secretion by increasing the levels of cyclic guanosine monophosphate in STC-1 cell lines. A parallel pathway for NO-mediated stimulation of adenosine triphosphate-sensitive K channels was suggested due to the inability of NO-generating agents to activate the channel. Furthermore, low levels of NO led to the depolarization of K channel basal membrane potential.

Cholecystokinin-58 (CCK-58) is a molecular form of CCK, a biologically active peptide. It is unique because of its inusually long length. However, this characteristic has made analysis of its immunoreactivity difficult as compared to the short forms of bioactive peptides. Herein, shorter fragments of CCK-58 were generated to determine whether length influences its biological activity. The results show that shorter fragments derived from CCK-58 are more immunoreactive than large forms of CCK-58.

The role of beta-adrenergic receptors (beta-AR) in the regulation of cholescystokinin (CCK) secretion in the CCK secreting cell line, STC-1, was investigated. Photolabeling studies and addition of isoproteronol into the solution showed increases in cAMP levels and CCK release, indicating a possible association between the two compounds. Cells treated with L-type calcium blocker diltiazem inhibited CCK secretion. These results suggest that beta-ARs are present in STC-1 cells and associated with cAMP production.

The role of the L- and T-type calcium channels in depolarization-mediated release of the hormone cholescystokinin (CCK) was investigated using the CCK-secreting cell line, STC-1. Barium-induced CCK release was inhibited by the two forms of L-type calcium blocker, nicardipine and diltiazem. The T-type calcium blocker, nickel chloride, failed to barium-induced CCK release. Analysis of the effects of the L-type calcium channel opener showed that depolarization of the plasma membrane, which was caused by inhibition of potassium channel activity, lead to the activation of L-type calcium channels.

The exposure to high fat content in diet enhances cholecystokinin (CCK) release and the pancreatic exocrine response to intraduodenal fat in rats. High fat content increases the secretion of fat-digesting enzymes in pancreatic juice, which enhances the hydrolysis rate of triglycerides into fatty acids. Fluid secretion remains high during the continuous infusion of fat, but enzyme secretion attains a peak and then declines.

The secretion of cholecystokinin (CCK) in the intestine is controlled by the monitor peptide and the intestinal CCK releasing factor. The monitor peptide is a 61 amino acid protein secreted into the pancreatic juice by the pancreas which in the intestine stimulates the secretion of CCK. The intestinal CCK releasing factor is produced by the intestine and stimulates the secretion of CCK when proteins and fat are ingested, bile-pancreatic juice is absent or protease inhibitors are present. The control of the secretion by these control factors is through a positive and a negative feedback mechanism.

Experimental observations including patch-clamp studies suggest a calcium-dependent pathway for the secretion of cholecystokinin (CCK) in STC-1 cells, stimulated by phenylalanine. Ten micromoles of diltiazem blocks this phenylalanine-induced CCK secretion. Pertussis toxin does not regulate this dose-dependent CCK release.

A study of the action of calcium in the bombesin-activated secretion of cholecystokinin (CCK) from intestinal CCK-generating cell-line (STC-1) through radioimmunoassay reveals that the secretion occurs through binding to a receptor and is influenced by enhanced (Ca2+)i. STC-1 cell line may facilitate the analysis of the modulation of intestinal CCK release. Bombesin induces a dose-dependent secretion of CCK, which requires calcium intake.

Experimental studies of the role of potassium channel activity in the secretion of cholecystokinin (CCK) in STC-1 cells reveal that the activity of basally active ATP-sensitive potassium channels tonically controls CCK release. Addition of glucose inhibits the channel activity, leading to depolarization of the plasma membrane and an increase in the cystolic calcium. The glucose-induced calcium release induces the secretion of CCK and a calcium channel blocker inhibits the glucose-induced CCK release. Patch-clamp and 86Rb efflux studies reveal the endogenous expression of ATP-sensitive potassium channels in STC-1 cells.

Cholecystokinin is a classical gastrointestinal hormone that is produced by discrete endocrine cells of the upper small intestine. Cholecystokinin is produced in various molecular forms that result from differences in posttranslation processing of a single gene product. Cholecystokinin is secreted from the intestine in response to the ingestion of food. We observed that specific dietary substances increase the rate of transcription of the cholecystokinin gene and stimulate cholecystokinin release in rats. In contrast the paracrine transmitter, somatostatin, inhibits dietary-stimulated cholecystokinin secretion and lowers intestinal mRNA levels. Evidence that cholecystokinin gene expression is not necessarily linked to hormone secretion is supported by the observation that the neuropeptide, bombesin, stimulates cholecystokinin release but does not modify intestinal cholecystokinin mRNA levels. To examine the intracellular messengers that might regulate the cholecystokinin cell directly, we developed an in vitro method for studying cholecystokinin release from isolated intestinal mucosal cells. In this perifusion system, cholecystokinin release was stimulated by membrane depolarizing concentrations of KCl (50 mmol/L), the calcium ionophore A23187 (1 [micro]mol/L), and the cAMP analogue dibutyryl cAMP (1 [micro]mol/L). Biologically active cholecystokinin was also released in a dose-dependent manner by the peptide transmitters, bombesin and monitor peptide. These findings indicate that neurotransmitters and hormones may directly regulate the cholecystokinin cell and suggest that the phosphoinositide and adenylate cyclase cascades mediate stimulated-cholecystokinin secretion. J. Nutr. 124: 1308S-1314S, 1994.

Estimation of plasma cholecystokinin (CCK) is measured following orgastric intake of protein hydrolysates, aminoacids, glucose, starch and protein. This determines CCK effusion from the proximal intestine, due to dietary component's interaction. Postprandial protein activation of CCK is assumed to be influenced by intraluminal trypsin. Peptidergei-and hormone-induced CCK effusion is studied by analyzng dispersed mucosal cell-perifusion.

Radioimmunoassay and patch-clamp recording techniques are used in the examination of secretory and electrophysiological properties of STC-1 cells which are cholecystokinin-secreting cell line. Exposure to agents caused the stimulation of cholecystokinin secretion and an increase in the level of intracellular calcium levels. The pretreatment using the calcium channel blocker diltiazem blocks the secretory effects of these agents. The electrophysiological and secretory mechanisms occurring in the cholecystokinin can be studied by the STC-1 cells.

Cholecystokinin (CCK) cells were isolated from a population of small intestinal mucosal cells using monitor peptide. The change in the fluorescence of CCK secretory cells provided an index for the identification of the cells in the intestinal mucosa which were then stained immunohistochemically and sorted. Ninety percent of the sorted cells stained positively which indicates that functional intestinal CCK cells can be enrichedusing fluorescence-activated cell sorting.

Capsaicin vanilloid receptor-1 mediates substance P release in experimental pancreatitis. Am J Physiol Gastrointest Liver Physiol 281: G1322-G1328, 2001.--We examined whether the capsaicin vanilloid receptor-1 (VR1) mediates substance P (SP) release from primary sensory neurons in experimental pancreatitis. Pancreatitis was achieved by 12 hourly injections of caerulein (50 [micro]g/kg ip) in mice. One group received capsazepine (100 [micro]mol/kg sc), a competitive VR1 antagonist, at 4-h intervals. Neurokinin-1 receptor (NK1R) internalization in acinar cells, used as an index of endogenous SP release, was assessed by immunocytochemical quantification of NK1R endocytosis. The severity of pancreatitis was assessed by measurements of serum amylase, pancreatic myeloperoxidase (MPO) activity, and histological grading. Caerulein administration caused significant elevations in serum amylase and pancreatic MPO activity, produced histological evidence of pancreatitis, and caused a dramatic increase in NK1R endocytosis. Capsazepine treatment significantly reduced the level of NK1R endocytosis, and this was associated with similar reductions in pancreatic MPO activity and histological severity of pancreatitis. These results demonstrate that repeated caerulein stimulation causes experimental pancreatitis that is mediated in part by stimulation of VR1 on primary sensory neurons, resulting in endogenous SP release. capsazepine; neurogenic inflammation; neurokinin-1 receptor; pancreatic acinar cells; primary sensory neurons