DECREASED NITRIC-OXIDE SYNTHASE ACTIVITY IN PLATELETS FROM IDDM AND NIDDM PATIENTS

Nitric oxide (NO) produced by platelet nitric oxide synthase (NOS) inh ibits platelet activation by increased cytoplasmic cGMP levels, The ai m of this study was to investigate platelet NOS activity in insulin-de pendent (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM), wh ich are characterized by enhanced platelet activation. HbA(1c) levels, platelet NOS and platelet membrane Na+/K+ ATPase activity were determ ined in 19 IDDM patients, 21 NIDDM patients and 31 healthy control sub jects, NOS activity was measured by a spectrophotometric method based on NO-dependent oxidation of oxyhaemoglobin to met-haemoglobin. Na+/K ATPase activity was measured by the method of Kitao and Hattori. Both NOS and Na+/K+ ATPase activity were significantly reduced in diabetic subjects compared with control subjects, NOS showed a significant neg ative relation with HbA(1c) levels and a positive relation with Na+/K ATPase activity in diabetic patients It is hypothesized that the decr eased NOS activity might play a role in the pathogenesis of diabetic v ascular complications.