Takahashi H, Yamaguchi M
Laboratory of Metabolism and Endocrinology, Graduate School of Nutritional Sciences, University of Shizuoka, Japan.
Mol Cell Biochem. 1993 Aug 25;125(2):171-7. doi: 10.1007/BF00936446.
The interaction of various hormones and regucalcin on (Ca(2+)-Mg2+)-ATPase activity in rat liver plasma membranes was investigated. The presence of epinephrine (10(-6)-10(-4) M), phenylephrine (10(-6)-10(-4) M), and insulin (10(-8)-10(-7) M) in the reaction mixture produced a significant increase in (Ca(2+)-Mg7+)-ATPase activity, while the enzyme activity was decreased significantly by calcitonin (3 x 10(-8)-3 x 10(-6) M). These hormonal effects, except for calcitonin, were clearly inhibited by the presence of vanadate (10(-4) M) which can inhibit the Ca(2+)-dependent phosphorylation of enzyme. Meanwhile, regucalcin (0.25 and 0.50 microM), isolated from rat liver cytosol, elevated significantly (Ca(2+)-Mg2+)-ATPase activity in the plasma membranes, although this elevation was not inhibited by vanadate (10(-4) M). The epinephrine (10(-5) M) or phenylephrine (10(-4) M)-induced increase in (Ca(2+)-Mg2+)-ATPase activity was disappeared in the presence of regucalcin; in this case the effect of regucalcin was also weakened. However, the inhibitory effect of calcitonin (3 x 10(-6) M) was not weakened by the presence of regucalcin (0.5 microM). Moreover, GTP (10(-5) and 10(-4) M)-induced increase in (Ca(2+)-Mg2+)-ATPase activity was not seen in the presence of regucalcin (0.25 microM). The present finding suggests that the activating mechanism of regucalcin on (Ca(2+)-Mg2+)-ATPase is not involved on GTP-binding protein which modulates the receptor-mediated hormonal effect in rat liver plasma membranes.
研究了大鼠肝细胞膜中各种激素与调钙素对（Ca(2 +)-Mg2 +）-ATP酶活性的相互作用。反应混合物中存在肾上腺素（10(-6)-10(-4) M）、去氧肾上腺素（10(-6)-10(-4) M）和胰岛素（10(-8)-10(-7) M）时，（Ca(2 +)-Mg7 +）-ATP酶活性显著增加，而降钙素（3×10(-8)-3×10(-6) M）则使该酶活性显著降低。除降钙素外，这些激素效应均被钒酸盐（10(-4) M）明显抑制，钒酸盐可抑制酶的Ca(2 +)依赖性磷酸化。同时，从大鼠肝细胞溶质中分离出的调钙素（0.25和0.50 microM）可显著提高细胞膜中（Ca(2 +)-Mg2 +）-ATP酶活性，尽管这种提高不受钒酸盐（10(-4) M）抑制。在存在调钙素的情况下，肾上腺素（10(-5) M）或去氧肾上腺素（10(-4) M）诱导的（Ca(2 +)-Mg2 +）-ATP酶活性增加消失；在这种情况下，调钙素的作用也减弱。然而，降钙素（3×10(-6) M）的抑制作用不受调钙素（0.5 microM）存在的影响。此外，在存在调钙素（0.25 microM）的情况下，未观察到GTP（10(-5)和10(-4) M）诱导的（Ca(2 +)-Mg2 +）-ATP酶活性增加。目前的发现表明，调钙素对（Ca(2 +)-Mg2 +）-ATP酶的激活机制不涉及在大鼠肝细胞膜中调节受体介导的激素效应的GTP结合蛋白。
