Inactivation of kallikrein and kininases and stabilization of whole rat brain kinin levels following focused microwave irradiation

Focused microwave irradiation was employed to stabilize endogenous whole rat brain bradykinin levels prior to a simple extraction procedure. Skull microwave exposure (2450 MHz, 3.8 kW., 2.45 sec) resulted in inactivation to less than 5% of control of whole brain kallikrein and kininase activity. Using this adequate exposure duration whole rat brain kinin levels as measured by a sensitive radio-immunoassay were approximately 0.6 pmol/g (wet weight). Further purification of irradiated brain extracts using HPLC revealed that immunoreactive kinin eluted as a single peak that co-chromatographed with authentic bradykinin. Microwave fixation duration of 1.25 sec yielded greatly increased levels of immunoreactive kinin which following HPLC purification eluted in two peaks, corresponding to authentic bradykinin and T-kinin, respectively. The tissue injury resulting from incomplete microwave fixation resulted in the release of kinins. This excess immunoreactive kinin may be derived from cerebral blood, since the predominant form of kinin-generating protein in plasma is T-kininogen.