ULTRASTRUCTURAL PATTERN OF GLUCAGON PRODUCING CELLS IN THE GASTRIC-MUCOSA OF THE DEVELOPING OPOSSUM DIDELPHIS-ALBIVENTRIS (MARSUPIALIA)

Gastric glucagon-producing cells of the pouch young, weaned and adult opossum Didelphis albiventris were investigated by immunocytochemical and ultrastructural methods. In sections of the oxyntic mucosa stained by immunoperoxidase it was observed that glucagon-immunoreactive cell s increased in number during pouch development (from 7.9+/-4.7 to 35.4 +/-5.9 cells/mm(2)), decreasing progressively to weaned (14.2+/-4.8 ce lls/mm(2)) and adult animals (10.4+/-3.0 cells/mm(2)). The glucagon-im munoreactive cells presented numerous electrondense, round cytoplasmic granules surrounded by a membrane. Frequently, the dense core of the granules was separated from the enveloping membrane by a delicate elec tronlucent halo or by a less electrondense peripheral halo. This patte rn of the granular component was similar to the ultrastructural morpho logy observed in pancreatic islet glucagon-producing cells and A-like cells of the gastric mucosa of those eutherian mammals studied so far.