Immunohistochemical Localization of Glucagon-Like-Peptide 1 in the Canine Embryo

GLP-1 is a peptide hormone highly conserved among mammals that derives from a tissue specific post-translational processing of the proglucagon gene. It is known to be produced in the intestinal L-cells as a consequence of pro-hormone convertase PC 1/3 cleavage of major proglucagon fragment. It has a role as “incretin” stimulating postprandial insulin synthesis and secretion, somatostatin release and inhibiting glucagon secretion. Recently a role has been assigned in embryological processes and in the differentiation of the pancreatic β-cells. Objective. The aim of this study was to describe GLP-1 distribution in the canine embryo. Methods. Paraffin sections obtained from 6 thirtydays canine embryos collected from two different mothers during hysterectomy were used in the present study. Immunolocalization of GLP-1 and Chromogranin-A was performed by using the peroxidase method. Colocalization studies were also accomplished by immunofluorescence. Results. We detected GLP-1 only in the developing primordial of pancreas where it did colocalize sometimes with Chromogranin-A. Intestinal presence of GLP-1 was not detected. Chromogranin-A was very seldom observed in the developing duodenum. Conclusions. Our results suggest an embryologic role of GLP-1 in pancreas organogenesis. This speculation is further corroborated by the recent literature data on the potential role of the α-cells in stimulating either the generation (embryos) or the re-generation of β-cells together with the GLP-1 ability to modulate different pathways involved in tissue morphogenesis and differentiation.