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Atrial natriuretic peptide (ANP), brain type natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) comprise a family of natriuretic peptides that mediate their biological effects through three natriuretic peptide receptor subtypes, NPR-A (ANP, BNP), NPR-B (CNP) and NPR-C (ANP, BNP, CNP). Several reports have provided evidence for the expression of ANP and specific binding sites for ANP in the pancreas. The purpose of this study was to identify the ANP receptor subtype and to localize its expression to a specific cell type in the human pancreas. NPR-C immunoreactivity, but neither ANP nor NPR-A, was detected in human islets by immunofluorescent staining. No immunostaining was observed in the exocrine pancreas or ductal structures. Double-staining revealed that NPR-C was expressed mainly in the glucagon-containing alpha cells. NPR-C mRNA and protein were detected in isolated human islets by RT-PCR and Western blot analysis, respectively. NPR-C expression was also detected by immunofluorescent staining in glucagonoma but not in insulinoma. ANP, as well as BNP and CNP, stimulated glucagon secretion from perifused human islets (1,111 +/- 55% vs. basal [7.3 fmol/min]; P < 0.001). This response was mimicked by cANP(4-23), a selective agonist of NPR-C. In conclusion, the NPR-C receptor is expressed in normal and neoplastic human alpha cells. These findings suggest a role for natriuretic peptides in the regulation of glucagon secretion from human alpha cells.

Background: Glucagon-secreting endocrine pancreatic tumor is a rare disease, hence controlled studies on clinical management are lacking. In an attempt to assess the efficacy of diagnostic and therapeutic measures in patients with glucagonoma, a retrospective study was performed using the archives of a tertiary care center., Patients and Methods: Records from 340 patients with endocrine pancreatic tumors were reassessed and 23 patients with malignant endocrine pancreatic tumor and elevated plasma glucagon levels were identified., Results: About 7% of patients with histologically verified tumors fullfilled our criteria for glucagonoma. Only 22% of these patients had developed diabetes prior to the diagnosis of glucagonoma. Seventy eight percent had metastatic disease to the liver at diagnosis. Necrolytic migratory erythema was diagnosed or clinically suspected in 52%. Somatostatin receptor scintigraphy was positive in 95%. Nineteen patients received chemotherapy at some point, in 18 cases streptozotocin and 5 FU. With this treatment, objective radiological responses were seen in 50% of evaluable patients. Other treatment modalities used were interferon, somatostatin analogs, hepatic artery embolization, radio-frequency ablation of liver metastases, and radiolabeled somatostatin analogs. During the study period, 11 patients died at a median of 80 months from diagnosis whereas 11 patients are still alive after a median follow up of 52 months. One patient was lost to follow-up., Conclusions: Glucagonomas represent 7% of our comprehensive referral material of endocrine pancreatic tumors. Necrolytic migratory erythema was a common finding (52%) and diabetes less frequent at presentation than previously reported. Tumors were positive on somatostatin receptor scintigraphy and objective responses were seen to chemotherapy.