In the developing pancreas of human embryos and fetusses (in weeks 4 to 20 of the intrauterine life) activities of aminopeptidase A (APA) and M (APM), dipeptidyl peptidase IV (DPP IV), and gamma-glutamyl transferase (GGT) were studied in cryostat sections using methods as recommended by Lojda (J. Histochem. Cytochem. 29, 481 (1981)). In the youngest embryos (4-7 weeks) a high DPP IV activity was recorded in the epithelium of differentiating primitive glandular tubules. Activity of other peptidase was low. In older fetusses (8-20 weeks, particularly after week 15) activities of all peptidases studied gradually increase. In acinic "anlage" a high DPP IV activity was observed. APM activity was substantially lower. The reaction product originating in the reaction for GGT is localized particularly at the luminal surfase of epithelial lining of primitive tubuli. In this period APA activity was hardly discernible. This is in contrast with other organs. High DPP IV and APM activities were present in cells of differentiating Langerhans islets. The appearance of peptidases studied does not occur simultaneously, however, their activities increase with the morphological differentiation.

Institut für Histologie und Embryologie Medizinische Fakultät Palacký Universität Olomouc Tschechoslowakei

Co-expression of the homologous proteases fibroblast activation protein and dipeptidyl peptidase-IV in the adult human Langerhans islets