Moorman J R, Zhou Z, Kirsch G E, Lacerda A E, Caffrey J M, Lam D M, Joho R H, Brown A M
Department of Medicine, University of Texas Medical Branch, Galveston 77550.
Am J Physiol. 1987 Oct;253(4 Pt 2):H985-91. doi: 10.1152/ajpheart.1987.253.4.H985.
Oocytes of Xenopus laevis, after microinjection with mRNA from rat heart, display typical high-threshold calcium (Ca) whole cell currents. To prepare to study structure-function relationships of the cardiac Ca channel molecule, we examined the fidelity of expression of biophysical and pharmacological properties at the molecular level. Cell-attached gigaseal recordings in five K-depolarized oocytes injected with adult rat heart mRNA showed single channel Ba currents with mean amplitude 1.3-1.5 pA at 0 mV, slope conductance 18-25 pS, and extrapolated reversal potential 57-68 mV. Openings were predominantly brief (mean 1.2 ms) but longer openings (mean 9 ms) were greatly enhanced in 10(-6) M BAY-K 8644, increasing the ensemble average current at 0 mV by more than fivefold. These features are typical of high-threshold cardiac Ca channels. In two patches from one injected oocyte, we saw multiple Ca channel conductances, as recently observed in other preparations. We conclude that X. laevis oocytes injected with adult rat heart mRNA produce high-threshold cardiac Ca channels with molecular properties identical to native cells.
用大鼠心脏的mRNA显微注射非洲爪蟾卵母细胞后，可显示典型的高阈值钙（Ca）全细胞电流。为了准备研究心脏钙通道分子的结构 - 功能关系，我们在分子水平上检查了生物物理和药理学特性表达的保真度。在五个注射了成年大鼠心脏mRNA的钾去极化卵母细胞中进行的细胞贴附式千兆封接记录显示，在0 mV时单通道钡电流的平均幅度为1.3 - 1.5 pA，斜率电导为18 - 25 pS，外推反转电位为57 - 68 mV。通道开放主要是短暂的（平均1.2毫秒），但在10（-6）M BAY - K 8644中，较长的开放（平均9毫秒）大大增强，使0 mV时的总体平均电流增加了五倍以上。这些特征是高阈值心脏钙通道的典型特征。在一个注射卵母细胞的两个膜片中，我们观察到了多个钙通道电导，这与最近在其他制备物中观察到的情况一样。我们得出结论，注射成年大鼠心脏mRNA的非洲爪蟾卵母细胞产生的高阈值心脏钙通道具有与天然细胞相同的分子特性。
