O6-Methylguanine-DNA methyltransferase status in neuroendocrine tumours: prognostic relevance and association with response to alkylating agents.

BACKGROUND: O(6)-Methylguanine-DNA methyltransferase (MGMT) loss of expression has been suggested to be predictive of response to temozolomide in neuroendocrine tumours (NETs), but so far, only limited data are available. We evaluated the prognostic and predictive value of MGMT status, assessed by two molecular methods and immunohistochemistry, in a large series of NETs of different origins. METHODS: A total of 107 patients, including 53 treated by alkylants (temozolomide, dacarbazine or streptozotocin), were retrospectively studied. In each case, we used methyl-specific PCR (MS-PCR) and pyrosequencing for evaluation of promoter methylation and immunohistochemistry for evaluation of protein status. RESULTS: MGMT promoter methylation was detected in 12 out of 99 (12%) interpretable cases by MS-PCR and in 24 out of 99 (24%) by pyrosequencing. O(6)-Methylguanine-DNA methyltransferase loss of expression was observed in 29 out of 89 (33%) interpretable cases. Status of MGMT was not correlated with overall survival (OS) from diagnosis. Progression-free survival and OS from first alkylant use (temozolomide, dacarbazine and streptozotocin) were higher in patients with MGMT protein loss (respectively, 20.2 vs 7.6 months, P<0.001 and 105 vs 34 months, P=0.006) or MGMT promoter methylation assessed by pyrosequencing (respectively, 26.4 vs 10.8 months, P=0.002 and 77 vs 43 months, P=0.026). CONCLUSIONS: Our results suggest that MGMT status is associated with response to alkylant-based chemotherapy in NETs.

Olmesartan-associated enteropathy: results of a national survey.

BACKGROUND: Recently, a new enteropathy has been described: olmesartan-associated enteropathy. However, the association has been questioned: a phase 3 trial and a cohort study found no association between gastrointestinal events and olmesartan. AIM: To collect French cases of sartan-associated enteropathy to describe further this entity, confirm or refute causality, and determine if the association exists with other sartans. METHODS: French gastroenterologists were invited to report cases of sartan-associated enteropathy and collect clinical, biological and histological data. Patients with diarrhoea and histological duodenal abnormalities were included. RESULTS: Thirty-six patients with olmesartan-associated enteropathy were reported, including 32 with villous atrophy and four without. There was only one patient with irbesartan-associated enteropathy. None of the patients died. Patients with villous atrophy had diarrhoea, vomiting, renal failure, hypokalaemia, body weight loss and hypoalbuminaemia. Thirty-one patients were hospitalised; four required intensive care. Anti-transglutaminase and anti-enterocyte antibodies were negative; anti-nuclear antibodies were positive (9/11). Endoscopic duodenal biopsies showed villous atrophy (32/32) and polyclonal intra-epithelial CD3+CD8+ lymphocytosis (11/11). Exactly, 14/15 patients responded to steroids and/or immunosuppressants, prescribed because of suspected autoimmune enteropathy. Ten olmesartan interruptions were followed by reintroductions before steroids or immunosuppressants. Interruptions were followed by remissions (9/10), but reintroductions were followed by relapses (9/9). Twenty-nine patients were in remission since olmesartan interruption, including 26 without immunosuppressants. Patients with normal villi had similar clinical characteristics, but mild histological abnormalities (intra-epithelial lymphocytosis and lamina propria lymphocytic infiltration). CONCLUSIONS: Olmesartan causes a severe and immune-mediated enteropathy, with or without villous atrophy. Enteropathy associated with other sartans seems to be very rare.

[Adult celiac disease with thrombosis: a case series of seven patients. Role of thrombophilic factors]. / Maladie cœliaque de l'adulte et thromboses : à propos de sept cas. Rôle des facteurs thrombophiliques.

PURPOSE: Thrombotic events may occur in celiac disease. In this study, we analyzed clinical features and risk factors for thrombosis in seven patients who had celiac disease and thrombosis. METHODS: We retrospectively studied 87 patients with adult celiac disease and identified seven cases of thrombosis. We searched if risk factors for thrombosis were identified and tested retrospectively antiphospholipid antibodies on the serum. RESULTS: In our study, the global prevalence of thrombosis was 8 %, and 5.7 % for spontaneous thrombosis, with venous thrombosis (n=5) or arterial thrombosis (n=1) or both (n=2). The seven patients consisted in six women and one man with a mean age of 44.8 years at time of thrombosis. Thrombotic events occurred before the diagnosis of celiac disease in four cases. In three cases, venous thrombosis was in unusual sites: portal (n=2), splenic vein thrombosis (n=1). In six cases, we identified risk factors for thrombosis, which could be linked to celiac disease: hyperhomocysteinemia (n=1), protein C and S deficiency due to vitamin K deficiency (n=3) and antiphospholipid antibodies (n=2). CONCLUSION: Such risk factors for thrombosis should be identified in patients in adult celiac disease in order to correct them and add a thromboembolic prophylaxis.

Contrast-enhanced harmonic endoscopic ultrasound in solid lesions of the pancreas: results of a pilot study.

BACKGROUND AND STUDY AIMS: Distinguishing pancreatic adenocarcinoma from other pancreatic masses remains challenging with current imaging techniques. This prospective study aimed to evaluate the accuracy of a new procedure, imaging the microcirculation pattern of the pancreas by contrast-enhanced harmonic endoscopic ultrasound (CEH-EUS) with a new Olympus prototype echo endoscope. PATIENTS AND METHODS: 35 patients presenting with solid pancreatic lesions were prospectively enrolled. All patients had conventional B mode and power Doppler EUS. After an intravenous bolus injection of 2.4 ml of a second-generation ultrasound contrast agent (SonoVue) CEH-EUS was then performed with a new Olympus prototype echo endoscope (xGF-UCT 180). The microvascular pattern was compared with the final diagnosis based on the pathological examination of specimens from surgery or EUS-guided fine-needle aspiration (EUS-FNA) or on follow-up for at least 12 months. RESULTS: The final diagnoses were: 18 adenocarcinomas, 9 neuroendocrine tumors, 7 chronic pancreatitis, and 1 stromal tumor. Power Doppler failed to display microcirculation, whereas harmonic imaging demonstrated it in all cases. Out of 18 lesions with a hypointense signal on CEH-EUS, 16 were adenocarcinomas. The sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy of hypointensity for diagnosing pancreatic adenocarcinoma were 89 %, 88 %, 88 %, 89 %, and 88.5 %, compared with corresponding values of 72 %, 100 %, 77 %, 100 %, and 86 % for EUS-FNA. Of five adenocarcinomas with false-negative results at EUS-FNA, four had a hypointense echo signal at CEH-EUS. CONCLUSIONS: CEH-EUS with the new Olympus prototype device successfully visualizes the microvascular pattern in pancreatic solid lesions, and may be useful for distinguishing adenocarcinomas from other pancreatic masses.

[Gastrointestinal stromal tumors (GIST)<5 cm in size: review of the literature and expert propositions for clinical management]. / Tumeurs stromales gastro-intestinales (GIST) de taille limitée (inférieure à 5cm): revue de la littérature et propositions pour la prise en charge.

Clinical recommendations for diagnosis, treatment and follow-up of GIST have been established. However, management of tumors limited in size, more often diagnosed by gastroenterologists, remains controversial. The aim of this work was in a first part to analyze the literature on GIST less than 5cm in size and in a second part to elaborate propositions for the clinical management based on an expert panel opinion.

Thirteen-month registration of patients with gastroenteropancreatic endocrine tumours in France.

The prevalence, clinical profiles and management of gastroenteropancreatic endocrine tumours (GEP) in France are not known. From August 1, 2001 to September 1, 2002, standardized records on patients with GEP were prospectively completed in 87 participating centres. The total group amounted to 668 patients (median age: 56 years, range: 12-89). WHO performance status was 0/1 for 80.2% of patients. The primary sites were the small bowel and colon (288), pancreas (211), unknown (77), stomach (33), non-digestive primary sites (24), appendix (20), rectum-anus (12), and oesophagus or cardia (3). GEP were functional in 260 patients (39%). Most pancreatic tumours were non-functional (72%). Metastatic disease was observed in 73.4% of cases. Most tumours (85.8%) were well or moderately differentiated. Somatostatin receptor scintigraphy was performed in only 55% of patients. The following treatment modalities were employed: resection of primary tumour: 66%; systemic chemotherapy: 41%; somatostatin analogues: 44 and 26% for GEP of small intestine and pancreas, respectively; interferon: 12%, and intra-arterial hepatic (chemo)embolization in 23 and 15% of GEP arising from the midgut and pancreas, respectively. Despite their low prevalence, well-differentiated GEP represent a significant and heterogeneous clinical group, which warrants improved medical education, referral to expert centres at an early stage, and the design of prospective therapeutic trials.

P53-mediated upregulation of DcR1 impairs oxaliplatin/TRAIL-induced synergistic anti-tumour potential in colon cancer cells.

Oxaliplatin has emerged as a major chemotherapeutic drug in the treatment of advanced colorectal cancer, yet like most conventional cancer therapeutics, its efficacy is often compromised due to p53 mutations. Unlike oxaliplatin, tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) triggers apoptosis in a p53-independent manner, and chemotherapy is known to overcome tumour resistance to TRAIL-induced cell death in most cancer cells. Using a panel of colon cancer cell lines, we assessed the ability of oxaliplatin to sensitize to TRAIL-induced apoptosis. We demonstrate that while both drugs additively or synergistically induced apoptosis in almost all cell lines tested, p53 wild-type colon cancer cells such as HCT116, LS513 or LS174T remained resistant. Impaired TRAIL-induced cell death resulted from a strong p53 dependent, oxaliplatin-mediated, DcR1 receptor expression increase. According to our finding, downregulation of DcR1 using siRNA, in p53 wild-type colon cancer cells, restored oxaliplatin/TRAIL synergistic apoptotic activity. On the contrary, exogenous DcR1 overexpression in SW480, a p53-mutated cell line, abolished the synergy between the two drugs. Altogether we demonstrate for the first time that p53 negatively regulates oxaliplatin-mediated TRAIL-induced apoptotic activity through DcR1 upregulation. Our findings could have important implications for future therapeutic strategies, and suggest that the association oxaliplatin/TRAIL should be restricted to patients harbouring a non-functional p53 protein.

Expression of beta-catenin in gastroenteropancreatic endocrine tumours: a study of 229 cases.

AIMS: To clarify the role of beta-catenin in digestive endocrine carcinogenesis, a large and representative series of gastroenteropancreatic endocrine tumours was analysed in order to determine the incidence and pattern of beta-catenin changes and to analyse the clinical and histological characteristics of the tumours presenting immunohistochemically detectable changes in beta-catenin expression. METHODS: 229 cases of gastroenteropancreatic endocrine tumours (stomach, 11; duodenum and ampulla, 29; jejunum and ileum, 51; appendix, 13; colon and rectum, 17; and pancreas, 108) were studied by immunohistochemistry to assess the pattern of distribution of beta-catenin (membranous, cytoplasmic or nuclear). DNA was analysed to detect mutations in exon 3 of the CTNNB1 gene. RESULTS: The distribution of immunoreactive beta-catenin protein was membranous in 164 cases, cytoplasmic in 58 cases and nuclear in seven cases. No mutation was detected in exon 3 of the CTNNB1 gene in any case. The seven cases with nuclear accumulation of beta-catenin were large tumours (mean size 44 (standard deviation (SD) 18.5) mm) with metastases, including liver metastases in five cases, high Ki-67 index (mean 34% (SD 16.5%)) and cyclin D1 overexpression; p53 accumulation was detected in six cases. Five patients died of disease; the mean (SD) survival was 13.6 (4.8) months. CONCLUSIONS: Immunohistochemically detectable nuclear accumulation of beta-catenin is infrequent in gastroenteropancreatic endocrine tumours and is usually not associated with mutations in CNNTB1 exon 3. Changes in beta-catenin expression are late events in digestive endocrine carcinogenesis, associated with tumour progression and dissemination.

Unusual cystic presentation of an endocrine carcinoma of the jejunum.

The cystic presentation of endocrine tumours is rare and raises difficult diagnostic problems. So far, the only cases of cystic digestive endocrine tumours reported in the literature are of pancreatic origin. We report the unusual observation of a jejunal endocrine carcinoma presenting as a cystic abdominal mass. A 59-year-old woman was referred for chest and abdominal pain. Imaging studies revealed multiple cystic nodules in the liver and a large sus-mesocolic cystic lesion of probable intestinal origin. Biopsies of the extra-hepatic mass and liver nodules showed endocrine tumour. Surgical resection of the jejunal mass and of liver segment III were performed. Histological examination confirmed the diagnosis of jejunal endocrine carcinoma metastatic to the liver. Large areas of the primary and secondary tumours presented an unusual vesicular architecture, responsible for the cystic presentation. No adjuvant treatment was attempted. This observation underlines the difficult diagnostic problems raised by the cystic presentation of digestive endocrine tumours.

Protein hydrolysates stimulate proglucagon gene transcription in intestinal endocrine cells via two elements related to cyclic AMP response element.

AIMS/HYPOTHESIS: Protein hydrolysates (peptones) increase not only glucagon-like peptide-1 (GLP-1) secretion but also transcription of the proglucagon ( PG) gene in the intestine. The critical physiological roles of gut-derived GLPs raised hope for their therapeutic use in several disorders, especially GLP-1 in diabetes. We aimed to investigate the molecular mechanisms involved in this nutrient- PG gene interaction. METHODS: Wild-type and mutated PG promoter fragments fused to the luciferase reporter gene were transfected into enteroendocrine STC-1 cells, which were then either treated or not with peptones. Co-transfection with expression vectors of dominant-negative forms of cAMP response element binding protein (CREB) and protein kinase A (PKA) proteins were performed, as well as electrophoresis mobility shift assays. RESULTS: Deletion analysis showed that the promoter region spanning between -350 and -292 bp was crucial for the transcriptional stimulation induced by peptones. Site-directed mutagenesis of the canonical cAMP response element (CRE(PG)) and of the adjacent putative CRE site (CRE-like1) led to a dramatic inhibition of the promoter responsiveness to peptones. Over expression of a dominant-negative mutant of CREB or of PKA produced a comparable and selective inhibitory effect on the activity of transfected promoter fragment containing the -350/-292 sequence. EMSA showed that CREB and fra2 transcription factors bound to CRE(PG) and CRE-like1 elements respectively, independently of peptone treatment. CONCLUSIONS/INTERPRETATION: Our report identified cis- and trans-regulatory elements implicated in the transcriptional control of PG gene by nutrients in enteroendocrine cells. It highlights the role of a previously unsuspected CRE-like1 element, and emphasises the importance of CRE-related sequences in the regulation of PG gene transcription in the intestine.

Interest of Chromogranin A for diagnosis and follow-up of endocrine tumours.

OBJECTIVE: To determine the interest of Chromogranin A (CgA) determination for diagnosis and follow-up in patients with gastroenteropancreatic endocrine tumours (GEP-ET) and multiple endocrine neoplasia type 1 (MEN-1). PATIENTS AND METHODS: CgA levels were measured with an immunoradiometric assay in 124 sporadic GEP-ET, 34 MEN-1 and 127 controls. Serial determinations were performed in 56 patients (212 visits). Changes in CgA levels over 25% were considered as significant. RESULTS: Using a cut-off value of 130 micro g/l, established from a receiver-operating characteristic curve, the specificity of CgA was 98.4%, with a sensitivity of 62.9%, higher in secreting than in nonsecreting tumours (73%vs. 45%; P < 0.003) and related to the extent of metastatic spreading (P < 0.001). In nonsecreting tumours, the positive predictive value (PPV) of CgA for the presence of metastases was 100% but the negative predictive value (NPV) was only 50%. In MEN-1, high CgA levels indicated a pancreatic tumour with a 100% specificity but the sensitivity was 59%. During the follow-up, the concordance between CgA and tumour evolution was 80%, whatever the secretory status. In patients with carcinoid tumours, the concordance was higher for CgA than for serotonin (81%vs. 54%; P < 0.001). CONCLUSION: Due to its high specificity, CgA determination may help to discriminate the endocrine character of a GEP tumour and to indicate a pancreatic tumour in MEN-1. However, its low NPV in nonsecreting tumours limits its interest for diagnosis and staging. By contrast, serial evaluation of CgA seems of particular interest for the follow-up of GEP-ET tumours.

Rab3a controls exocytosis in cholecystokinin-secreting cells.

The expression of rab3A and rab3D isoforms in the enteroendocrine, cholecystokinin-secreting, cell lines STC-1 and GLUTag is here demonstrated. In contrast, rab3B is undetectable in these two cell lines, and rab3C is only slightly expressed in GLUTag cells. Using a transient co-transfection system with human growth hormone as reporter protein, we show that overexpression of the GTPase-deficient mutant rab3AQ81L, but not rab3DQ81L, significantly decreases human growth hormone secretory responses to various agonists in STC-1 cells. These results indicate that endocrine cell lines of intestinal origin express rab3A and rab3D proteins, but the GTP-bound form of rab3A only acts as a negative modulator in the control of cholecystokinin secretion from STC-1 cells.

Effect of bile salts on colonic mucus secretion in isolated vascularly perfused rat colon.

Mainly composed of mucins, mucus secreted by goblet cells in the intestinal epithelium is critically involved in the protection of the gastrointestinal mucosa. The hypothesis that bile and some bile salts can induce mucus secretion was tested in the isolated perfused rat colon. Mucus release was evaluated using enzyme-linked immunosorbent assays and supported by histological analysis. Luminal administration of bile extract (1%) provoked mucus secretion in the rat colon. Deoxycholate (0.5-10 mM) induced a dose-dependent increase in rat colonic mucus release. Chenodeoxycholate (10 mM) and hyodeoxycholate (10 mM) also evoked mucus discharge, whereas 10 mM cholate, 10 mM ursodeoxycholate, or Tween-20 did not release mucus. Taurine-conjugated bile salts (deoxycholate, hyodeoxycholate, and chenodeoxycholate) were less potent mucus secretagogues than the corresponding unconjugated forms. The deoxycholate-induced mucus discharge was not altered by pharmacological blockers (tetrodotoxin, atropine), indomethacin, mast cell stabilizers (ketotifen, doxantrazole), H1 histamine receptor antagonist (pyrilamine), or 5-HT receptor antagonists (ketanserin, ondansetron, SDZ 205-557). Our findings suggest that some bile salts, especially in the unconjugated form, may provoke colonic mucus secretion, probably through a direct action on mucus-secreting cells.

Cystic endocrine tumors of the pancreas: clinical, radiologic, and histopathologic features in 13 cases.

Cystic endocrine tumors of the pancreas are rare and raise difficult clinical problems. Our aims were to reevaluate the diagnostic and therapeutic strategy and to assess their histopathologic characteristics. Thirteen cystic endocrine tumors diagnosed in 10 patients were included. Clinical, radiologic, and pathologic data were reviewed. There were 6 male and 4 female patients (median age, 46 yrs). Six patients had evidence of multiple endocrine neoplasia type 1 (MEN1) disease. Four had a functional endocrine syndrome. Ten tumors were visible on imaging studies. The most suggestive radiologic features were the existence of a peripheral hypervascular rim (10 cases) and images of cyst into cyst (two cases). On gross and histologic examinations, two distinct types were present. Macrocystic tumors (six cases) were unilocular and limited by a thick wall containing nests of tumor cells. Microcystic tumors (seven cases) were characterized by the presence of multiple cystic spaces directly lined by tumor cells. Surgical resection was performed in all cases. Three patients had lymph node metastases at the time of diagnosis. One patient is dead with metastatic dissemination. The others are alive without recurrence or metastasis. The diagnosis of endocrine tumor must be considered for any pancreatic cyst discovered in a patient with a history of MEN1 syndrome or with clinical features suggestive of this syndrome. Cystic pancreatic endocrine tumors must be treated by surgical resection because of their possible malignant evolution.

CCK expression in enteroendocrine cell is regulated by soluble factor(s) from underlying fibroblasts.

Studies on the cross-talk between the intestinal epithelium and the underlying connective tissue have concentrated on enterocytes. In contrast, little is known about the interactions between the mesenchymal compartment and the enteroendocrine cells, scattered among the other cell types of the epithelium. To address this question, a panel of coculture systems between the enteroendocrine STC-1 cell line and three intestinal myofibroblastic cell lines (MIC) was used in order to assess different levels of regulation, namely cell-cell and cell-matrix interactions, and the role of diffusible factors. We demonstrate that the expression of cholecystokinin, a typical intestinal hormone produced by STC-1 cells, is up-regulated in the presence of a fibroblastic environment through a paracrine pathway involving FGF2. Concomitantly, STC-1 cell morphology and proliferation were also modulated, but through distinct mechanisms according to the origin of fibroblasts. The results reveal definite epithelio-mesenchymal interactions that may be critical for the maintenance of phenotype and function of enteroendocrine cells.

Peptones stimulate intestinal cholecystokinin gene transcription via cyclic adenosine monophosphate response element-binding factors.

Cholecystokinin (CCK) is a potent intestinal hormone that regulates several digestive functions. Despite the physiological importance of CCK, the cellular and molecular mechanisms that govern its synthesis and secretion are not completely identified. Peptones, which are fair counterparts of the protein fraction in the intestinal lumen, are good stimulants of CCK secretion. We have previously shown that peptones activate CCK gene transcription in STC-1 enteroendocrine cells. The DNA element(s) necessary to induce the transcriptional stimulation was preliminary, localized in the first 800 bp of the CCK gene promoter. In the present study, we identify a DNA element [peptone-response element (PepRE)] essential to confer peptone-responsiveness to the CCK promoter, and we characterize the transcription factors implicated. Localization of the PepRE between -93 and -70 bp of the promoter was established using serial 5'-3'deletions. Systematic site-directed mutagenesis demonstrated that the core PepRE sequence, spanning from nucleotide -72 to -83, overlapped with the putative AP-1/CRE site. Mutations in the core sequence dramatically decreased peptone-responsiveness of CCK promoter fragments. The PepRE functioned as a low-affinity CRE consensus site, binding only transcription factors of the CREB family. Overexpression, in STC-1 cells, of a dominant-negative protein (A-CREB), that prevented the binding of CREB factors to DNA, completely abolished the peptone-induced transcriptional stimulation. Peptone treatment did not modify the nature and the abundance of proteins bound to the PepRE but led to increased phosphorylation of the CREB factors. In conclusion, the present study first demonstrates that CCK gene expression is under the control of protein-derived nutrients in the STC-1 enteroendocrine cell line.

Involvement of beta1- and beta2- but not beta3-adrenoceptor activation in adrenergic PYY secretion from the isolated colon.

The secretion of PYY by endocrine L cells of the terminal gut is under the control of nutrients, the autonomic nervous system and hormones. Catecholamines, and the non-specific beta-adrenergic agonist isoproterenol induce PYY secretion from rat isolated colon or ileum. Because beta3-adrenergic receptors now appear to mediate many of the effects of catecholamines in the gastrointestinal tract, we investigated the involvement of beta1-, beta2-, and beta3-adrenoceptor stimulation in PYY secretion from the isolated, vascularly perfused rat colon. Infusion of 10(-6) M isoproterenol induced a transient increase in PYY secretion (from 36+/-4 to 87+/-20 fmol/2 min; n=7, P<0.05), that was abolished by a previous infusion of the beta1- and beta2-adrenergic blocker (and partial beta3-agonist) alprenolol (10(-6) M). The beta1-adrenergic agonist dobutamine and the beta-2 agonist terbutaline also (both at 10(-5) M) significantly stimulated PYY secretion, from 29+/-1 to 79+/-12 fmol/2 min and from 19+/-1 to 73+/-13 fmol/2 min respectively (n=7, P<0.05). Neither of the beta3-adrenergic agonists tested (BRL 37 344 (10(-5), 10(-6) M) and SR 58 611A (10(-6) M)) significantly stimulated PYY secretion, thus confirming the exclusive involvement of beta1- and beta2-receptors in beta-adrenergic agonist induced hormone secretion.

Selective involvement of calcium and calcium channels in stimulated mucin secretion from rat colon.

BACKGROUND: The cellular mechanisms involved in the mucin secretion of rat colon are unknown. The objective of the present study was thus to determine the role of extracellular calcium and of L-type calcium channels in rat intestinal mucin discharge. METHODS: The experiments were conducted using the isolated vascularly perfused rat colon. Mucin secretion was evaluated using an enzyme-linked immunosorbent assay. RESULTS: Intra-arterial bethanechol (200 microM) or luminal deoxycholate (5 mM) produced a significant mucin discharge (609% and 386% of controls, respectively). The colonic mucin output induced by these two secretagogues was significantly inhibited by arterial administration of EGTA (2 mM), verapamil (100 microM) or nifedipine (50 microM). In contrast, luminal EGTA (2 mM) had no inhibitory effect. Intra-arterial infusion of the calmodulin antagonist trifluoperazine (10 microM) also reduced mucin discharge induced by bethanechol or deoxycholate (304% and 223% of controls, respectively). Colonic mucin secretion was significantly stimulated after intra-arterial infusion of 3-isobutyl-methylxanthine (IBMX, 100 microM) or forskolin (2-20 microM). Stimulation by forskolin was unaffected by arterial EGTA, verapamil, nifedipine or trifluoperazine. CONCLUSION: In the isolated vascularly perfused rat colon, mucin discharge induced by bethanechol or deoxycholate requires extracellular calcium and the activation of voltage-dependent calcium channels of L-type. In contrast, forskolin does not appear to stimulate mucin release by increasing calcium entry.