Inhibition by epsilon-aminocaproic acid of the activation of the first component of the complement system.

The influence of EACA on C1 in whole human serum and on C1 and C (see article) as isolated molecules was assessed hemolytically. There was selective inhibition of C1 without effect on the levels of C4, C2, C3, and C9 in whole human serum that was reversed by dialysis. EACA was found to inhibit the intrinsic activation of C1 without inhibiting the already active molecule. This was confirmed by the capacity of trypsin to uncover C1 activity in cellular intermediates formed by C1 treated with EACA that did not evolve in the absence of this extrinsic activating mechanism. Inasmuch as the trypsin-dependent recovery of C1 was incomplete, an effect on binding cannot be excluded.