飯匙倩心臟毒對紅血球細胞膜之作用

Abstract

飯匙倩心臟毒在代用血漿中使紅血球細胞溶血作用可分為三個步驟：第一，這種毒素能夠在細胞解體前很快地與細胞膜結合，這種結合能力不受溫度影響，但稍微受四種無機鹽離子的阻礙。由反應速率的研究顯示這種毒素在細胞膜外有二種結合位置。而且此毒素之抗體也無法使它自細胞表面脫離。 第二，當這種毒素在37°C下，可經由結合後再轉入它在細胞內部的作用處，因而使得細胞變得非常脆弱。 第三，經過前二步驟之後，必須再經過一段長時間(六小時)方能使細胞全破，同時低溫也會阻礙前二階段該毒素之攻擊，除此而外，磷酸脂水解?可強化它的毒性。然而，另外一種人工合成的聚合蛋白(Polylysine)卻和此毒素不同，它不會使細胞膜脆弱，同時它也不受溫度和磷酸水解?之影響。

Chronologically, there were three stages in the hemolysis of 0.25% human erythrocytes caused by 7.15 μM cardiotoxin in plasma expander. First, the toxin could bind to membrane rapidly before the cells disrupted. Binding of (125 I)-toxin to intact erythrocytes was temperature independent and decreased slightly by any one of the four inorganic salts inculding NaCl, KCl, CaCl2 and MgCl2 at 10 mM concentration. Kinetic studies revealed the presence of two toxin binding sites on the extracellular membrane: one with high affinity (equilibrium association constant Ka=2.7x10(6) M(-1), low capacity (4.76x10(6)，molecules/cell); the second with low affinity (Ka=9.33*10(3) M(-1), high capacity (2.12x10(8) molecules/cell). Anti-toxin antibody could not dissociate the bound toxin from the cell surface. Second, the bound toxin at 37℃ transversed and reached its action site at inner membrane whereon somehow a interaction resulted in loosing the membrane rigidity and thereby effected the cells less resistant to lower osmotic pressure. This event took place within 25 min in the non-lytic period. Third, the hemolysis subsequent to the second stage took place and it took around 6 h to complete the lysis of all cells. The events in both second and third stages were suppressed when the interaction of toxin with erythrocytes at 37℃ were proceeded in the presence of either the inorganic salts at 10 mM concentration or anti-toxin antibody. The interaction at 15℃ abolished completely this two events. Phospholipase A2 enhanced the disruption of human erythrocytes once their membrane rigidity was loosed by the toxin. Unlike the situation of the toxin, polylysine did not loose the membrane rigidity. Its induction in hemolysis showed no temperature-dependence and was neither suppressed by the inorganic salts nor potentiated by phospholipase A2.