The effect of hyperglycemia on isolated rodent islets transplanted to the kidney capsule site

The effect of hyperglycemia on transplanted rat pancreatic islets was studied using a new technique for transplanting a defined number of islets in a blood clot. Normal or streptozotocin-diabetic DA rats were given 400 DA islets under the left kidney capsule (a number shown to be insufficient to reverse diabetes). After 2 weeks the diabetic rats were given a further 1000 islets under the right kidney capsule to reverse diabetes. Kidneys from both groups were examined at 2 weeks after the initial islet implant and at 3 months for both gross and histological appearance and for insulin content. After 2 weeks left kidneys from nondiabetic rats showed abundant islet tissue, with an insulin content of 116 (+/- 14 SEM) milliunits, compared to 1 +/- 0.5 milliunits in the right kidney. Kidneys from diabetic rats showed no islets recognizable grossly. Histological examination showed vacuolated tissue scarcely recognizable as islet tissue, and the insulin content of the left kidney was reduced to 18 +/- 5 milliunits. However, 3 months after reversal of diabetes by transplantation of 1000 islets to the right kidney, histologically "normal" islet tissue was again visible on the left kidney, and the insulin content was 160 +/- 36 milliunits. Islets left in normal animals for 3 months contained 195 +/- 50 milliunits. These experiments show that islets implanted beneath the kidney capsule in diabetic rats are not destroyed by two weeks hyperglycemia. This suggests that protection of islets after implantation by insulin treatment is unnecessary, even in the presence of a persistently raised blood sugar.