IGF-2-like peptides are present in insulin cells of the elasmobranchian endocrine pancreas: an immunohistochemical and chromatographic study.
Evidence for the presence of peptides, related to insulin-like growth factor 2 (IGF-2), has been obtained in the endocrine pancreas of the elasmobranchian species Raja clavata, the sting ray. By radioimmunoassay, IGF-2-like immunoreactivity was detected in Raja pancreas extract. Further characterization of this activity by acid gel chromatography revealed two distinct peaks of IGF-2-like immunoreactivity with apparent molecular weights of approximately 8.2 kDa and 4.5 kDa. Using the same IGF-2 antibody as well as antisera specific for mammalian IGF-1, insulin, glucagon, somatostatin and pancreatic polypeptide in double immunofluorescence studies, IGF-2-like immunoreactivity was located exclusively in insulin-immunoreactive cells. In contrast, IGF-1-like immunoreactivity was mainly observed in somatostatin- and glucagon-immunoreactive cells. A varying proportion (0-70%) of insulin-immunoreactive cells, however, displayed both IGF-1- and IGF-2-like immunoreactivity. Absorption studies indicated that the IGF-2-like peptides in Raja are different from mammalian and submammalian insulin and mammalian IGF-1, but similar to mammalian IGF-2. Thus, IGF-2-like peptides seem to occur during evolution as early as the phylogenetic development of the elasmobranchians. Furthermore, the results indicate a particularly conservative evolution of the islet IGF-2 system.
Reinecke
M
M
Institute of Anatomy, University of Zürich, Switzerland.
Weimar
E
E
Maake
C
C
Drakenberg
K
K
Falkmer
S
S
Sara
V R
VR
D000818:Animals; D002845:Chromatography; D003911:Dextrans; D005260:Female; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D007335:Insulin-Like Growth Factor II / Q000032:analysis* / Q000276:immunology; D007515:Islets of Langerhans / Q000737:chemistry*; D008297:Male; D010187:Pancreatic Hormones / Q000032:analysis; D011817:Rabbits; D011869:Radioligand Assay; D012860:Skates, Fish / Q000378:metabolism*
D003911:Dextrans; D010187:Pancreatic Hormones; D007335:Insulin-Like Growth Factor II; C025614:sephadex