Sha Qun, Robinson Shawn W, McCulle Stacey L, Shorofsky Stephen R, Welling Paul A, Goldman L, Balke C William
Department of Medicine, School of Medicine, University of Maryland, Baltimore, MD 21201, USA.
J Physiol. 2003 Mar 1;547(Pt 2):435-40. doi: 10.1113/jphysiol.2002.035246. Epub 2003 Jan 24.
ICa(TTX) is a sodium current component, functionally distinct from the main body of sodium current, seen in cardiac and other cells. To determine if ICa(TTX) channels are a separate isoform from the classical cardiac sodium channels, we exposed rat ventricular cells in primary culture to an antisense oligonucleotide (AON) directed against rH1 (rNav1.5): 5'-CTCCTCATACCCTCT-3'. The homologous human sequence has been identified (and confirmed by us on HEK 293 cells) as effective against hH1 expressed heterologously. Scrambled sequence (5'-CCCCCCTTATCTACT-3') controls were also included. The AON (10 microM; day 2 of exposure) reduced the classical sodium current by 69.6 % compared to untreated and 60.8 % compared to scrambled sequence (10 microM; day 2 of exposure) controls (mean +/- S.E.M. maximum peak inward current density of -8.23 +/- 0.60 pA pF-1, 18 cells, for untreated; -6.37 +/- 0.79 pA pF-1, 16 cells, for scrambled sequence; and -2.50 +/- 0.31 pA pF-1, 18 cells, for AON-treated cells). The two control groups are not significantly different from each other, but are both significantly different from the AON-treated group (P < 0.001). The inhibition was specific for sodium channels, with no significant AON effect on the L-type calcium current. This confirms that H1 generates the classical cardiac sodium current. This same AON at the same concentration and time of exposure had no significant effect on ICa(TTX) (mean of -4.72 +/- 0.55, 15 cells; -5.47 +/- 0.53, 13 cells; and -5.04 +/- 0.63 pA pF-1, 15 cells, for untreated controls, scrambled controls and AON treated, respectively). Hence, ICa(TTX), which is functionally distinct from the classical cardiac sodium current, is encoded by a distinct gene.
河豚毒素敏感的内向钙电流（ICa(TTX)）是一种钠电流成分，在功能上与钠电流主体不同，可见于心脏和其他细胞中。为了确定ICa(TTX)通道是否是与经典心脏钠通道不同的一种亚型，我们将原代培养的大鼠心室细胞暴露于针对rH1（rNav1.5）的反义寡核苷酸（AON）：5'-CTCCTCATACCCTCT-3'。已鉴定出同源的人类序列（我们在HEK 293细胞上进行了验证）对异源表达的hH1有效。还设置了乱序序列（5'-CCCCCCTTATCTACT-3'）作为对照。与未处理组相比，AON（10微摩尔；暴露第2天）使经典钠电流降低了69.6%，与乱序序列（10微摩尔；暴露第2天）对照组相比降低了60.8%（未处理组18个细胞的平均±标准误最大内向电流峰值密度为-8.23±0.60皮安/皮法，乱序序列组16个细胞为-6.37±0.79皮安/皮法，AON处理组18个细胞为-2.50±0.31皮安/皮法）。两个对照组之间无显著差异，但均与AON处理组有显著差异（P<0.001）。这种抑制作用对钠通道具有特异性，AON对L型钙电流无显著影响。这证实了H1产生经典的心脏钠电流。相同浓度和暴露时间的该AON对ICa(TTX)无显著影响（未处理对照组、乱序对照组和AON处理组的平均电流分别为-4.72±0.55、-5.47±0.53和-5.04±0.63皮安/皮法，每组各15个或13个细胞）。因此，在功能上与经典心脏钠电流不同的ICa(TTX)是由一个不同的基因编码的。
