The changes in pancreatic somatostatin content and release were studied in streptozotocin (STZ)-diabetic rats. Male Wistar rats were treated with a graded dose of STZ (group I, 0; II, 25; III, 50; IV, 75 mgμkg), which produced various grades of diabetic rats four weeks later. The pancreatic somatostatin content increased in proportion to the dose of STZ (1,189 ± 31; II, 222 ± 20; III, 343 ± 4; IV, 515 ± 36 ngμg wet wt), while graded reductions of insulin content were observed. Significant increases in glucagon content were found only in groups III and IV. Pancreatic somatostatin release increased during arginine infusion (19.2 mM) dose dependently, (I, 543 ± 36; II, 946 ± 64; III, 1229 ± 55; IV, 2186 ± 150 pg/15 min), and it correlated with the graded decreases of insulin release. The glucagon release induced by arginine, however, did not change significantly.
These results indicate that pancreatic somatostatin content and release increased in STZ-diabetic rats in proportion to the degree of insulin deficiency.