An immunohistochemical study on the pancreatic endocrine cells of the three-toed sloth, Bradypus variegatus.
The cellular composition and relative frequency of the occurrence of pancreatic endocrine cells were studied immunohistochemically in a primitive eutherian and arboreal folivore, the three-toed sloth, since previous histochemical and ultrastructural studies on the endocrine pancreas of the sloth have detected only a single islet cell type, the A cell. In the sloth pancreas, four types of endocrine cells immunoreactive for glucagon, insulin, somatostatin and serotonin (5-hydroxytryptamine) were found as reported in the pancreas of human and common experimental mammals, but pancreatic polypeptide-immunoreactive cells were not detected by either avian- or bovine-pancreatic polypeptide antiserum. The endocrine cells were distributed mainly in the islets and partly also in the exocrine tissue including the pancreatic ducts. Larger or smaller clusters consisting of glucagon- and insulin-immunoreactive cells were also found frequently in the interlobular connective tissue. In the islets, glucagon- and insulin-immunoreactive cells were the most prominent cell type, while somatostatin- and serotonin-immunoreactive cells were sparse. The most striking feature in the sloth pancreas is the high frequency of glucagon-immunoreactive cells, because these cells are by far less in number than insulin-immunoreactive cells in the islets of human and common experimental mammals. This appears to be an intriguing characteristic of the sloth pancreas in a possible relation to the animal's unique metabolic system and the phylogenetical position.
Department of Histology and Embryology, Federal University of Pernambuco, Recife, Brazil.
D L
DL
da Mota
J
J
Yamada
L L
LL
Gerge
P B
PB
Pinheiro
D000818:Animals; D005260:Female; D005934:Glucagon / Q000032:analysis; D007150:Immunohistochemistry; D007328:Insulin / Q000032:analysis; D008297:Male; D010179:Pancreas / Q000737:chemistry / Q000166:cytology*; D012701:Serotonin / Q000032:analysis; D012896:Sloths / Q000033:anatomy & histology*; D013004:Somatostatin / Q000032:analysis
D007328:Insulin; D012701:Serotonin; D013004:Somatostatin; D005934:Glucagon