Plasma bradykinin release. Bradykinin formation in Lewis rat plasma containing kinin inhibitor. The contact system of citrated Lewis (○) and Buffalo (•) rat plasma containing 1,10-phenanthrolene (2.5 mM) was activated by activation with kaolin. At the indicated time, an aliquot was removed and tested for the levels of bradykinin. Mean ± SD, n = 3. *P < .05, ** P < .01 by Student t test.