Kwak B R, Jongsma H J
Department of Medical Physiology and Sports Medicine, Utrecht University, The Netherlands.
Mol Cell Biochem. 1996;157(1-2):93-9. doi: 10.1007/BF00227885.
Short term (15 min) effects of activators of protein kinase A (PKA), PKC and PKG on cardiac macroscopic (g(j)) and single channel (gamma j) gap junctional conductances were studied in pairs of neonatal rat cardiomyocytes. Under dual whole-cell voltage-clamp, PKC activation by 100 nM TPA increased g(j) by 16 +/- 2% (mean +/- S.E.M, n = 9), 1.5 mM of the PKG activator 8-bromo-cGMP (8Br-cGMP) decreased g(j) by 26 +/- 2% (n = 4), whereas 1.5 mM of the PKA activator 8Br-cAMP did not affect g(j) (1 +/- 5%, n = 11). Single cardiac gap junction channel events, resolved in the presence of heptanol, indicated two gamma j sizes of 20 pS and 40-45 pS. Under control conditions, the larger events were most frequently observed. Whereas 8Br-cAMP did not change this distribution, TPA or 8Br-cGMP shifted the gamma j distribution to the lower sizes. Diffusion of 6-carboxyfluorescein (6-CF), a gap junction permeant tracer, from the injected cell to neighboring cells was studied on small clusters of neonatal rat cardiomyocytes. Under control conditions, 6-CF labeled 8.4 +/- 0.4 cells (mean +/- S.E.M, n = 31). Whereas 8Br-cAMP did not change the extent of dye transfer (8.1 +/- 0.5 cells, n = 10), TPA restricted the diffusion of 6-CF to 2.2 +/- 0.2 cells (n = 30) and 8Br-cGMP to 3.5 +/- 0.3 cells (n = 10). This suggests that permeability and single channel conductance of Cx43 gap junction channels are parallel related. Altogether, these results point to the differential modulation of electrical and metabolic coupling of cardiac cells by various phosphorylating conditions.
在新生大鼠心肌细胞对中，研究了蛋白激酶A（PKA）、蛋白激酶C（PKC）和蛋白激酶G（PKG）激活剂对心脏宏观（g(j)）和单通道（γj）缝隙连接电导的短期（15分钟）影响。在双全细胞电压钳制下，100 nM佛波酯（TPA）激活PKC使g(j)增加16±2%（平均值±标准误，n = 9），1.5 mM的PKG激活剂8-溴环鸟苷（8Br-cGMP）使g(j)降低26±2%（n = 4），而1.5 mM的PKA激活剂8-溴环腺苷（8Br-cAMP）对g(j)无影响（1±5%，n = 11）。在庚醇存在下分辨出的单个心脏缝隙连接通道事件显示有两种γj大小，分别为20 pS和40 - 45 pS。在对照条件下，较大的事件最常被观察到。虽然8Br-cAMP没有改变这种分布，但TPA或8Br-cGMP将γj分布转向较小的尺寸。在新生大鼠心肌细胞小簇上研究了缝隙连接通透性示踪剂6-羧基荧光素（6-CF）从注射细胞向相邻细胞的扩散。在对照条件下，6-CF标记8.4±0.4个细胞（平均值±标准误，n = 31）。虽然8Br-cAMP没有改变染料转移范围（8.1±0.5个细胞，n = 10），但TPA将6-CF的扩散限制到2.2±0.2个细胞（n = 30），8Br-cGMP限制到3.5±0.3个细胞（n = 10）。这表明Cx43缝隙连接通道的通透性和单通道电导呈平行关系。总之，这些结果表明不同的磷酸化状态对心脏细胞的电耦合和代谢耦合有不同的调节作用。
