Effect of zinc on lysis of sheep erythrocytes by guinea pig C4-deficient serum.

The divalent cation Zn2+ enhanced the lysis of sheep erythrocytes (ShE) by guinea pig C4-deficient (C4D) serum. Enhancement by Zn2+ (0.1 mM) was demonstrated in the presence of cobra venom factor (CoVF, 2 units/ml) and optimal Mg2+ (1.0 mM). Moreover, Zn2+ (0.1 mM) in the presence of Mg2+ (1.0 mM) caused the lysis of ShE by C4D serum without the addition of CoVF. Further studies were therefore performed in the absence of CoVF. Although addition of Zn2+ or Mg2+ alone to some pools of C4D serum caused lysis of ShE, the greatest extent of lysis occurred when Zn2+ and Mg2+ were both added to the reaction mixtures. When C4D serum was resin-treated, both Mg2+ and Zn2+ were required for lysis. Addition of Ca2+ had no effect. This pathway required high concns of serum and was inhibited by pretreating the serum with zymosan (2 mg/ml serum, 37 degrees C, 1 hr) or by heating the serum at 56 degrees C for 20 min. K76-COOH monocarboxylic acid also inhibited this pathway. These results suggest that Zn2+ together with Mg2+ activates the alternative pathway on the nonactivator surface (ShE).