Inducible nitric oxide synthetase is expressed in adult but not fetal pig pancreatic islets

Cytokine-induced expression of inducible nitric oxide synthetase (iNOS) and production of nitric oxide (NO) by pancreatic islet cells has been suggest ed as one potential mechanism for beta cell destruction. In this study, we investigated the role of iNOS and NO in islet primary non-function. Islets were assessed for their function, viability and expression of iNOS. Adult r at and pig islets isolated by collagenase digestion and fetal pig pancreas (FPP) grafts isolated by collagenase digestion or high oxygen culture were transplanted into C57BL6 mice and nude mice. iNOS protein was detected by i mmunohistochemistry. iNOS protein was found in normal rat and pig pancreas and adult rat and pig islets that were isolated by collagenase digestion an d transplanted into either C57BL6 mice or nude mice. iNOS was not detected in fetal pig islet grafts, regardless of whether collagenase was used in th e isolation process. In adult pig islet grafts, the presence of iNOS protei n correlated with high levels of islet cell apoptosis and primary non-funct ion. Despite the persistent presence of iNOS in rat islets, there was no ev idence that it had a deleterious effect on rat islet viability, or function . Therefore, in isolated adult pig islets, there was a correlation between iNOS expression and apoptosis, suggesting that iNOS activation may be delet erious to the adult pig islets. However, other factors such as the fragilit y of the islet capsule may be equally important. By contrast, fetal pig isl ets did not express iNOS and this may be an important reason for their enha nced viability when compared with adult islet tissue.