Insulin degradation. XXVIII. Immunocytochemical localization of glutathione-insulin transhydrogenase in the pancreas, kidney and liver of normal and streptozotocin-diabetic rats and of lean and obese (ob/ob) mice.

Glutathione-insulin transhydrogenase catalyzed the inactivation of insulin by splitting the hormone into A and B chains. We have localized this enzyme immunocytochemically by light microscopy in the pancreas, kidney and liver of both lean and obese (ob/ob) mice and similarly in normal and streptozotocin-diabetic rats. Localization was achieved by an antibody to glutathione-insulin transhydrogenase using a peroxidase-antiperoxidase technique. In comparison with tissues from control animals, positive immunostaining for glutathione-insulin transhydrogenase was increased in the obese mouse but reduced in the diabetic rat. Different tissues showed considerable variation in the amount of glutathione-insulin transhydrogenase which could be detected. In the pancreatic islets there was little or no evidence for the presence of the enzyme in peripheral cells. In the kidney, immunocytochemical staining was found only in the proximal tubules. In the liver there was a generalised distribution of the enzyme, but the greatest concentration was in the periportal region. These observations parallel the biochemical data relating to glutathione-insulin transhydrogenase, indicating that different amount of insulin degrading activity exist in different regions of tissues.