Tissue-specific pattern of angiotensin-converting enzyme 2 expression in rat pancreas.

Angiotensin-converting enzyme 2 (ACE2), a carboxypeptidase that is highly homologous to ACE, acts as a negative regulator for the renin-angiotensin system (RAS). Pancreatic RAS is thought to play important endocrine and exocrine roles in hormone secretion. Further exploration of this system is likely to offer new insights into the pathogenesis of pancreatic diseases such as diabetes mellitus. This study investigated the expression of ACE2 in rat pancreatic exocrine and endocrine tissue. Reverse transcription-polymerase chain reaction, immunoblotting and immunohistochemistry showed that ACE2 mRNA and protein were expressed in the pancreas. Immunoelectron microscopy demonstrated that ACE2 was expressed in both endocrine and exocrine pancreatic tissues. In the endocrine tissue, ACE2 was localized on the secretory granules. Double immunofluorescence labelling showed that ACE2 was co-localized with both insulin and somatostatin, while it was rarely co-localized with glucagon and pancreatic polypeptide. These findings suggest that ACE2 might play an important role in glucose homeostasis.