Human tissue kallikrein (hK1) is reduced in hypertension, cardiovascular and renal diseases. There is little information on the participation of hK1 in type 1 diabetes mellitus (DM), type 2 DM, and gestational diabetes mellitus (GDM), respectively. The aim of this study was to evaluate the roles of insulin and hyperglycemia on urinary hK1 activity in type 1 DM and in GDM. Forty-three type 1 DM patients (5-35 years, disease duration <= 5 years, receiving insulin, HbA(1c) > 7.6%) were selected. Forty-three healthy individuals, paired according to gender and age, were used as controls. Thirty GDM patients (18-42 years, between the 24th and 37th week of pregnancy, recently diagnosed, not under insulin therapy) were also selected. Thirty healthy pregnant (18-42 years, between the 24th and 37th week of pregnancy) and 30 healthy non-pregnant women (18-42 years) were selected as controls. Random midstream urine was used. hK1 amidase activity was estimated with D-Val-Leu-Arg-Nan substrate. Creatinine was determined by Jaffe's method. hK1 specific amidase activity was expressed as mu M/(min mg creatinine) to correct for differences in urine flow rate. hK1 specific amidase activity was significantly higher in the urine of type 1 DM than in controls, and in the urine of GDM patients than in healthy pregnant women and healthy nonpregnant women, respectively. The data suggest that hyperglycemia, rather than insulin, is involved in the mechanism of increased hK1 specific amidase activity in both type 1 DM and GDM patients, respectively. (C) 2011 Elsevier Inc. All rights reserved.