24 week old non-diabetic Wistar (Nondiabetic) and diabetic GK (diabetic) rats were treated for 4 weeks with 166 mg/kg-chow linagliptin (Nondiabetic+Linagliptin, Diabetic+Linagliptin). (A). Blood glucose levels were assessed via tail vein puncture before and after treatment. While the diabetic rats had significantly elevated blood glucose levels compared to the nondiabetic rats, no significant changes were observed in either group following treatment. (B). Linagliptin treatment reduced plasma ET-1 levels significantly in the diabetic rats, however they were not returned to the plasma levels observed in the nondiabetic rats. Results are expressed as mean ± SEM, n=3–5, ***p<0.001 vs Nondiabetic, ###p<0.001 vs Diabetic.