Histological and immunohistochemical studies of the endocrine pancreas of lizards

Summary The endocrine pancreas of the grass lizard, Mabuya quinquetaeniata, and of the desert lizard, Uromastyx aegyptia, was investigated histologically and immunohistochemically. In both lizard species four cell types were observed in the endocrine pancreas, namely insulin (B), glucagon (A), somatostatin (D) and pancreatic polyeptide (PP) cells. In both species the B, A and D cells could be detected by their cross-reactivity with antisera raised against mammalian insulin, glucagon and somatostatin. However, these cells showed different tinctorial properties in the two lizard species. In both species the endocrine tissues were concentrated in the splenic lobe of the pancreas. In the grass lizard the endocrine tissue in the splenic lobe consisted mainly of B, A and D cells and in the ventral lobe the major cell types were PP and D cells. In the desert lizard, on the other hand, the frequency and the pattern of orientation of B, A and D cells were the same in both the splenic and the ventral lobes, but PP cells in the ventral lobe outnumbered those of the splenic lobe. The PP and D cells scattered in the exocrine parenchyma and the long protrusions which they exhibited suggested that these cells exerted paracrine control on the acinar cells. It is speculated that this control by PP cells may be trophic and by D cells inhibitory.