KININOGEN CHANGES IN HUMAN PLASMA FOLLOWING A TEST MEAL OR INSULIN ADMINISTRATION

Ln healthy, fasted volunteers, the ingestion of a test meal produced w ithin 30 min, a decrease of ca. 40% of high molecular weight kininogen (HK) in plasma. Return to control (fasting) levels occurred after 90- 120 min. Low molecular weight kininogen (LK) remained unchanged or was slightly elevated. On another occasion, the same group of fasted volu nteers received an intravenous, euglycemic-clamped infusion of insulin . This treatment reproduced the effects of the test meal on HK. Insuli n had no effect on kininogen following incubation with plasma or whole blood. Slight systemic hypotension and increased leg muscle blood flo w accompanied postprandial plasma kininogen change. It is suggested th at such vascular changes may in part, be due to bradykinin (BK) releas ed from HK cleaved at vascular, possibly endothelial sites activated b y insulin following its release by alimentary stimulation. A decreased capacity to release BK due to absence of, or lowered sensitivity to, insulin may play a role in the origin of hypertension in diabetes.