the effects of human new pressor protein and coagulation factor xiia on blood pressure and heart rate in bilaterally nephrectomized rats

background: new pressor protein (npp) is a human plasma enzyme structurally related to b–fragment of activated factor xіі (β-fxiia). the objective of the present study was to investigate the effects of npp and β-fxiia on systolic blood pressure and heart rate in bilateral nephrectomized rats.   methods: forty male wistar rats (250-300 g) were sham-operated or bilaterally nephrectomized under anesthesia with a combination of halothane, nitrous oxide and oxygen. twenty four hours later under anesthesia with inactin (100 mg/kg), they were ganglion blocked (pentolinium tartrate; 19.2 mg/kg), and their systolic blood pressure and heart rate were measured before and after intravenous administration of captopril (2.5 mg/kg), npp (20 μ l plasma equivalent) or purified β-fxiia (300 ng/kg).   results: npp raised the systolic blood pressure by 31±2 mmhg and heart rate by 19±2 bpm in sham-operated rats. captopril caused systolic blood pressure and heart rate to increase significantly by 64±7 mmhg and 107±9 bpm, respectively in response to npp. in bilateral nephrectomized rats, npp raised systolic blood pressure by 57±6 mmhg and heart rate by 70±13 bpm in the absence of captopril, which were not significantly different from those (46±3 mmhg and 75±8 beats/min) in the presence of captopril.   conclusion: this study shows that the effects of npp and β-fragment of factor xіі on systolic blood pressure and heart rate are similar, suggestive of a functional relationship between them. the findings might suggest that the potentiation effect of captopril in sham-operated or bilaterally nephrectomized rats is primarily expressed via renal enzymes.