Effect of captopril on inactive renin and contact phase of coagulation system.

It has been suggested that a Factor XII-plasma Prekallikrein dependent pathway might play an important role in the activation of inactive renin. Since Captopril has the potential to affect the kinin-kallikrein system, we have studied in a group of 16 patients with essential hypertension its acute effect both on the levels of active, inactive and total renin, and on the contact phase of the coagulation system. Our results show that a single dose of Captopril (25 mg) induces a rapid and persistent increase of active and total renin, while inactive renin tends to decrease. Together with blood pressure, plasma Prekallikrein(PK), Factor XII(FXII) and Factor XI(FXI) concomitantly decrease, although not significantly, and their values seem to return to basal levels soonafter. However, no correlation was found at any time between the levels of any of these coagulation factors, including PK, and those of inactive, active or the ratio inactive/total renin. In spite of that, it is still possible that an activation of PK, which is likely to occur under Captopril administration, may affect at least the conversion of vessel-bound prorenin rather than the circulating form.