One study analyzed the metabolism of endogenous bradikinin (B2 receptor agonist) and its active metabolite, des-Arg9-Bradikinin (B1 receptor agonist) in the presence of an ACE-inhibitor during in vitro contact activation of plasma from hypertensive patients who presented angioedema and these kinetic parameters were compared with those measured in a control group (without angioedema) of hypertensive patients. Here, ACE is linked to angioedema.