The effect of a large dose of cortisol (5 mg/kg), injected 24h and 3h before or 3h and 24h after streptozotocin (SZ), on the course of SZ-induced diabetes has been studied in the rat. Glucose tolerance tests, performed 1 or 2, 8, and 30 days after the SZ injection (35 mg/kg), gave the same results in cortisol-treated rats regardless of the time of cortisol injection [before SZ (C.SZ) or after it (SZ.C)]. During the first test, elevated plasma glucose, decreased glucose tolerance, and decreased glucose-induced insulin secretion were present in SZ, C.SZ, and SZ.C rats. During the second and the third tests, glucose tolerance and insulin secretion were significantly improved in both groups of cortisol-treated rats. On the contrary, rats receiving only SZ showed a worsening of the diabetic state. It should be noted that cortisol-induced recovery of diabetes was not obtained with larger doses of SZ (50 mg/kg).
These findings indicate that an improvement of diabetes can be obtained by cortisol treatment after the onset of chemically induced diabetes. Whether this effect is obtained through an effect on pancreatic regeneration and/or through the anti-inflammatory properties of glucocorticoids is unknown at the present time.