Adrenomedullin: localization in the gastrointestinal tract and effects on insulin secretion.
Adrenomedullin is a novel hypotensive adrenal polypeptide originally isolated from a human pheochromocytoma and is structurally related to calcitonin gene-related peptide and islet amyloid polypeptide. Using immunocytochemistry, the occurrence of adrenomedullin in the adrenal gland and gastro-entero-pancreatic region in the rat was examined and its effect on insulin secretion from isolated rat islets was determined. Adrenomedullin-like immunoreactivity occurred in noradrenaline- and adrenaline-producing cells in the adrenal gland. Gastrointestinal endocrine cells, with increased density distally, displayed adrenomedullin-like immunoreactivity; these cells constituted a subpopulation of the enterochromaffin (serotonin-containing) cells. Co-localization of adrenomedullin with somatostatin, glicentin, gastrin/cholecystokinin, peptide YY or islet amyloid polypeptide was not encountered. Adrenomedullin-immunoreactive cells were not observed in the pancreatic islets. At 1, 10 and 100 nmol/l, adrenomedullin stimulated insulin release from isolated rat islets in the presence of 3.3 mmol/l glucose (P < 0.05) and at 100 nmol/l, the peptide potentiated insulin secretion also in the presence of 8.3 mmol/l glucose (P < 0.05). These findings suggest that, besides being an adrenal hypotensive peptide, adrenomedullin may be a gut hormone with a potential insulinotropic function.
Mulder
H
H
Department of Physiology and Neuroscience, University of Lund, Sweden. hindrik.mulder@mphy.lu.se
Ahrén
B
B
Karlsson
S
S
Sundler
F
F
D000311:Adrenal Glands / Q000378:metabolism; D053607:Adrenomedullin; D000818:Animals; D046508:Culture Techniques; D004064:Digestive System / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism; D010455:Peptides / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D007328:Insulin; D010455:Peptides; D053607:Adrenomedullin