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Inactivation of endotoxin by a humoral component. III. Role of divalent cation and a dialyzable component.

The uniformly high potency of citrated plasma as compared with the limited capacity of serum to inactivate endotoxin in vitro was found to be a consequence of the anticoagulant employed in collecting the plasma. Addition of calcium to plasma suppressed the activity of its endotoxm detoxifying component (EDC) whereas the addition of calcium-binding anticoagulants rendered serum comparable to plasma. Dialysis of plasma resulted in a marked reduction of its EDC activity despite the concommittant elimination of calcium. EDC activity could then be fully restored upon the addition of calcium-binding anticoagulants. Resin-treated plasma, without added anticoagulant, had EDC activity equal to plasma obtained with calcium-binding anticoagulants. Following dialysis, resin-treated plasma also sustained a marked reduction in EDC activity which could be fully restored by calcium-binding anticoagulants. Restoration was also obtained with the dialysate even after ashing. These findings indicated that the suppression of EDC activity by calcium is not direct but is mediated through its effects on an anionic component of plasma which is required for inactivation of endotoxin by EDC.

Bacteria↗

Studies on a proteolytic enzyme in human plasma. VIII. The effect of calcium and strontium ions on the activation of the plasma proteolytic enzyme.

Calcium ions accelerated the activation of the proteolytic enzyme of plasma from its precursor in the globulin fraction. Calcium did not appear to potentiate fibrinolysis by active bovine or human plasma proteolytic enzyme, nor did it accelerate the activation of the precursor of this enzyme by chloroform or by streptokinase. Experiments with partially purified plasma proteolytic enzyme suggested that the acceleratory effect of calcium was mediated indirectly. Since the concentration of calcium which was effective was comparable to that present in plasma, it is possible that the phenomena reported are of biological significance.

Animals↗

The influence of calcium ions on the inactivation of human complement and its components by plasmin.

Ca(++) potentiates the inactivation of human complement by streptokinase-activated plasmin and chloroform-activated bovine plasmin. The optimum concentration of Ca(++) varies between 10(-2)M and 10(-3)M, decreasing with increasing concentrations of streptokinase. The susceptibility of the components of complement to inactivation by plasmin is different in the presence and absence of Ca(++). C'2 and C'4 are most readily inactivated by plasmin in the presence of Ca(++), while C'1 disappears first in the absence of Ca(++). A large part of this C'1 disappearance is due to spontaneous inactivation. Similarities are pointed out between the influence of Ca(++) on the inactivation of the components of complement by antigen-antibody systems and by plasmin.

Animals↗