Sulfonylurea Effects on Glucagon Regulation During Hypoglycemia in Type 1 DM

Inclusion Criteria: * Patients aged 18 to 50 years * Patients diagnosed with C-peptide negative diabetes type 1 (C-peptide \<200 pmol/L 6 min after 1 mg glucagon i.v. at plasma glucose concentrations between 5 and 11 mmol/l) * Patients diagnosed with C-peptide positive diabetes type 1 (C-peptide \> 500 pmol/l 6 min after 1 mg glucagon i.v. at plasma glucose concentrations between 5 and 11 mmol/l) * Stable metabolic control; HbA1c levels \<8.0 % and without episodes of antecedent severe hypoglycemias in the past four weeks Exclusion Criteria: * Patients treated with medications potentially interfering with glucose metabolism, such as systemic steroids, immunosuppressive drugs (cyclosporine, tacrolimus, sirolimus), highly active antiretroviral therapy * History coronary artery disease * History of epilepsy or seizures * Current smokers * Any significant or unstable hepatic, cardiac, pulmonary, renal, neurological, musculoskeletal, hematological or endocrine disease. * Pregnant or breast feeding women * Woman of childbearing potential not using a reliable method of birth control such as oral contraceptives or IUD. * Subjects refusing or unable to give written informed consent