钙对心肌ATP酶的损害及镁的保护作用

The Effect of Magnesium on the Inhibition of Cardiac Sarcolemmal ATPase Elicited by Calcium

本工作在大鼠心肌肌膜观察到,Mg^(2+)为心肌Na^+-K^+-ATP酶激活所不可缺少的因素,当Mg^(2+)浓度在0～6mM时,Na^+-K^+-ATP酶及Mg^(2+)-ATP酶活性与其密切相关;当超过8 mM时,ATP酶总活性不变,但Na^+-K^+-ATP酶/Mg^(2+)-ATP酶之比值增高。高浓度Ca^(2+)对于Na^+-K^+-ATP酶及Mg^(2+)-ATP酶均具有抑制作用,而提高Mg^(2+)浓度可部分地拮抗高Ca^(2+)的损伤作用。

Magnesium is an essential cofactor of the sarcolemmal ATPase. A variation in the medium Mg2+concentration from 0 to 6 mM gives a dose-dependent change in activity of the enzyme system. When Mg2+ concentration is above 8 mM, it increases the activity due to Na++K++Mg2+. The Na++K++Mg2+/ Mg2+ activity ratio is therefore increased. Incubation of sarcolemma vesicles with high concentration Ca2+ leads to a decrease of the activating effect of either Na+ + K+ +Mg2+or Mg2+ alone. This inhibition of the enzyme activity by Ca2+ is partially antagonized by high concentration of Mg2+.