Studies on the subcellular localization and role of glutathione-insulin transhydrogenase in rat liver

125I-insulin was shown to be internalized in vivo to a discrete population of low-density membranes (ligandosomes), distinct from the +Golgi, endoplasmic reticulum, plasma membrane, and lysosomes. However, analytical subcellular fractionation shows that glutathione-insulin transhydrogenase is localized to the endoplasmic reticulum. Measurement of the specific enzyme activity of glutathione-insulin transhydrogenase showed no differences between normal, diabetic, and hyperinsulinaemic rats. These results suggest that glutathione-insulin transhydrogenase is not directly involved in the subcellular processing of receptor-bound internalized insulin.