Rise of plasma t-PA fibrinolytic activity in a group of maturity onset diabetic patients shifted from a first generation (tolbutamide) to a second generation sulphonylurea (gliclazide).
During treatment with tolbutamide 10 maturity onset diabetic patients had no detectable activity of tissue-type plasminogen activator (t-PA) determined on two occasions 3 months apart. All 10 patients responded on the change in treatment to gliclazide with an increase in activity of t-PA. However, after 12 months of treatment the t-PA activity in one of the 10 patients returned to the baseline level, whereas the remaining nine patients had a sustained increased t-PA activity compared to the period during treatment with tolbutamide. The concentration in plasma of t-PA antigen under basal conditions and after stimulation (venous occlusion) increased significantly during the period of treatment with gliclazide. The plasma concentrations of plasminogen activator inhibitor remained unchanged throughout the study. In contrast to these findings seven patients with marked activities of t-PA during treatment with tolbutamide retained unchanged levels of the variables reported above after a change in treatment to gliclazide. Serum glucose, HBA1c, apolipoproteins A and B, and triglycerides remained constant throughout the study, whereas serum cholesterol showed a decrease in both groups of patients after 3 months (P less than 0.05) as well as after 12 months (P less than 0.05) of treatment with gliclazide. There was no significant relationship between serum cholesterol concentrations and plasma concentrations of t-PA antigen indicating that the increase in t-PA antigen was independent of the metabolic state of the patients.