POTENT BLOOD-PRESSURE RAISING EFFECTS OF ACTIVATED COAGULATION-FACTOR-XII

A new presser protein (NPP) in trypsin-activated human plasma was rece ntly reported, whose blood pressure raising effects in bioassay rats a re potentiated 300% after treatment with angiotensin I converting enzy me inhibitors (captopril). Pure NPP sheaved good N-terminal sequence h omology with coagulation factor beta FXIIa, and little of it was prese nt in FXII-deficiency plasmas (greater than or equal to 99%, n = 4), T he present experiments confirm this in four additional FXII-deficiency plasmas. Further, ii) adding highly purified coagulation FXII, alpha FXIIa, or beta FXIIa fragment restores presser activity to such plasma s, but only after activation with trypsin. (ii) Such requirement for t rypsin suggests that no factor is structurally identical with NPP to b egin with but that all can be activated to NPP, (iii) When injected di rectly by vein, only beta FXIIa is presser, suggesting closest structu ral resemblance to NPP and (or) readiest endogenous conversion to NPP. (iv) NPP and beta FXIIa arts cardiotonic: they both raise systolic pr essure more than the diastolic, with a concomitant increase in heart r ate. These observations support NPP's structural relationship with bet a FXIIa and connect coagulation and blood pressure mechanisms in a new way, whose significance to the physiology and pathophysiology of bloo d pressure regulation remains to be established.