Eschenhagen T, Laufs U, Schmitz W, Scholz H, Warnholtz A, Weil J, Schäfer H J
Abteilung Allgemeine Pharmakologie, Universitäts-Krankenhaus, Hamburg, Germany.
J Mol Cell Cardiol. 1995 Oct;27(10):2249-63. doi: 10.1016/s0022-2828(95)91659-8.
We investigated the expression pattern of the heterotrimeric G proteins Gs alpha, Gi alpha-2 and Go alpha in rat and guinea-pig heart by in situ hybridization. Cryosections were hybridized with single-stranded 35S-cRNA probes complementary to subtype-specific sequences of the respective mRNAs. Hybridization signals were visualized by exposition to X-ray films and dipping autoradiography. The rank order of abundance was Gi alpha-2 approximately Gs alpha >> Go alpha. In general, G protein alpha-subunit mRNAs were evenly distributed in the heart including endo- and epicardium, large vessels and valves. Go alpha-mRNA levels were significantly higher in atria than in ventricles. In contrast to the rather uniform labeling of working myocardium, expression of all three G proteins was enriched in small intramural blood vessels and in subendocardial Purkinje fibers of septum and papillary muscles. A more marked enrichment of Gs alpha-, Gi alpha-2- and especially Go alpha-mRNA was seen in neuronal ganglionic cells in the atrial septum and posterior regions of the atrium. The main finding, however, was an enrichment of all three G protein mRNAs in the atrioventricular conductive tissue. The accumulation was strictly co-localized with acetylcholinesterase-positive regions identified as the atrioventricular node, the bundle of His and the right and left bundle branches and was seen similarly in rat and guinea-pig hearts. Quantitative in situ hybridization revealed Gs alpha-, Gi alpha-2- and Go alpha-mRNA levels in the bundle of His to be 206 +/- 0.13%. 191 +/- 0.15% and 165 +/- 0.06%, respectively, of that in the surrounding interventricular working myocardium. These findings indicate that heterotrimeric G proteins play an important role in modulation of electrical conductance in the heart.
我们通过原位杂交研究了异源三聚体G蛋白Gsα、Giα-2和Goα在大鼠和豚鼠心脏中的表达模式。将冷冻切片与与各自mRNA亚型特异性序列互补的单链35S - cRNA探针杂交。通过X射线胶片曝光和浸涂放射自显影来观察杂交信号。丰度顺序为Giα-2≈Gsα>>Goα。一般来说，G蛋白α亚基mRNA在心脏中均匀分布，包括心内膜和心外膜、大血管和瓣膜。Goα - mRNA水平在心房中显著高于心室。与工作心肌相当均匀的标记不同，所有三种G蛋白的表达在小的壁内血管以及隔膜和乳头肌的心内膜下浦肯野纤维中富集。在房间隔和心房后部的神经节细胞中，Gsα、Giα-2尤其是Goα - mRNA有更明显的富集。然而，主要发现是所有三种G蛋白mRNA在房室传导组织中富集。这种积累与被确定为房室结、希氏束以及左右束支的乙酰胆碱酯酶阳性区域严格共定位，并且在大鼠和豚鼠心脏中情况相似。定量原位杂交显示，希氏束中Gsα、Giα-2和Goα - mRNA水平分别是周围心室工作心肌中相应水平的206±0.13%、191±0.15%和165±0.06%。这些发现表明异源三聚体G蛋白在心脏电传导调节中起重要作用。
