Influence of streptozotocin-induced diabetes on the concentration of immunoreactive somatostatin in the retina and peripheral blood of the rat: effect of insulin treatment

Changes in somatostatin-like immunoreactivity (SLI) were examined in the retina and peripheral blood of diabetic rats treated with streptozotocin (STZ) and insulin. There was no change in retinal SLI content at 4 and 11 days after administration of STZ but, thereafter, SLI increased progressively in the diabetic animals by 220% at 18 days and 300% at 27 days. Plasma SLI levels increased by 500% at 11 days and maintained similar levels thereafter. Diabetic animals treated with insulin (3-5 i.u. daily) for 27 days showed a significant (P less than 0.01) decrease of retinal and plasma SLI levels compared with untreated diabetic animals. It is concluded that there is a significant increase of retinal and plasma SLI levels in diabetic rats which tends to normalize after several days of insulin treatment.