Bradykinin, a nonapeptide, is a potent endothelium-dependent vasodilator that operates via bradykinin receptors B1 and B2. Bradykinin Ile-Ser (T-Kinin) has a biological profile similar but not identical to bradykinin which is more resistant to degradation by kininase angiotensin converting enzyme (ACE). Bradykinin Ile-Ser is used to differentiate bradykinin receptor specificity and function.