Takeo S, Duke P, Taam G M, Singal P K, Dhalla N S
Can J Physiol Pharmacol. 1979 May;57(5):496-503. doi: 10.1139/y79-075.
Effects of lanthanum on Ca2+-ATPase, Mg2+-ATPase, Na+-K+-ATPase, and calcium binding activities were studied in rat heart sarcolemma. Ten to 100 micrometers lanthanum depressed significantly the Ca2+-ATPase activity and 50--200 micrometers lanthanum inhibited the calcium binding activity. Lineweaver-Burk plots of the Ca2+-ATPase activity showed that the inhibition by lanthanum was competitive with calcium concentration. Neither Mg2+-ATPase nor Na+-K+-ATPase activities were affected by lanthanum when the assay medium contained 1 mM EDTA; however, in the absence of EDTA, these enzyme activities were significantly decreased by 10--100 micrometers lanthanum. Rat hearts perfused with HEPES buffer containing 0.5 mM lanthanum showed electron-dense deposits restricted to the outer cell surface and the sarcolemma obtained from these hearts also had the deposits, indicating that the membrane fraction isolated by the hypotonic shock--LiBr treatment method is of sarcolemmal origin. The Ca2+-ATPase activity of the sarcolemma isolated from lanthanum-perfused hearts, unlike the Mg2+-ATPase, Na+-K+-ATPase, and calcium binding activities, was significantly less than the control value. From these observations it is suggested that lanthanum may influence calcium movement across the sarcolemma by affecting sarcolemmal ATPase and calcium binding activities.
研究了镧对大鼠心肌肌膜中Ca2+-ATP酶、Mg2+-ATP酶、Na+-K+-ATP酶及钙结合活性的影响。10至100微米的镧显著降低Ca2+-ATP酶活性，50至200微米的镧抑制钙结合活性。Ca2+-ATP酶活性的Lineweaver-Burk图表明，镧的抑制作用与钙浓度呈竞争性。当测定介质中含有1 mM乙二胺四乙酸（EDTA）时，Mg2+-ATP酶和Na+-K+-ATP酶活性均不受镧的影响；然而，在没有EDTA的情况下，10至100微米的镧会使这些酶活性显著降低。用含有0.5 mM镧的HEPES缓冲液灌注的大鼠心脏显示，电子致密沉积物仅限于细胞外表面，从这些心脏获得的肌膜也有沉积物，这表明通过低渗休克-LiBr处理方法分离的膜部分源自肌膜。与Mg2+-ATP酶、Na+-K+-ATP酶及钙结合活性不同，从用镧灌注的心脏分离的肌膜的Ca2+-ATP酶活性显著低于对照值。从这些观察结果推测，镧可能通过影响肌膜ATP酶和钙结合活性来影响钙跨肌膜的转运。
