1. Plasma prorenin is an inactive form of renin that is converted into active renin at alkaline pH in previously acidified plasma; this conversion of prorenin into renin is mediated by Hageman factor-dependent activation of prekallikrein, which, in turn, leads to prorenin activation.
2. Since plasma kallikrein can activate plasminogen, the present studies were designed to evaluate whether alkaline-phase activation of prorenin by plasma kallikrein is mediated via plasminogen activation.
3. We demonstrated that plasminogen is present in acid-treated plasma in sufficient quantity to convert prorenin into renin after activation by streptokinase.
4. However, alkaline-phase activation was completely normal in plasminogen-free plasma.
5. Therefore alkaline-phase activation of plasma prorenin is mediated by plasma kallikrein but is not dependent on kallikrein activation of plasminogen.