钙对心肌ATP酶的损害及镁的保护作用

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。

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

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+.