Wu S N, Yu H S
Department of Physiology, Kaohsiung Medical College, Taiwan, R.O.C.
Jpn J Physiol. 1993;43(2):177-89. doi: 10.2170/jjphysiol.43.177.
The role of adenosine action in modulating the action potential duration (APD) of single isolated guinea-pig atrial myocytes during beta-adrenergic stimulation with isoproterenol was investigated. Membrane potential and ionic currents were measured by the tight-seal, whole-cell patch-clamp technique. Adenosine (10 microM) antagonized isoproterenol (20 nM)-stimulated L-type calcium inward current (ICa). In the presence of isoproterenol, adenosine (10 microM) also increased holding and late outward currents. Isoproterenol (20 nM) caused a significant prolongation in atrial action potential at the level of 0 mV, rather than at 90% repolarization. Adenosine shortened atrial action potential dose-dependently in the presence of isoproterenol. The respective values for EC50 and maximally shortened action potential duration at 0 mV of adenosine with or without isoproterenol (20 nM) were 3.0 vs. 2.2 microM and 42.9 vs. 30.4 ms. In summary, during beta-adrenergic stimulation with isoproterenol, in guinea-pig atrial myocytes, adenosine elicited the specific K(+)-outward current and concomitantly attenuated the isoproterenol-stimulated ICa. These phenomena may account for the modulation of atrial action potential by adenosine with or without isoproterenol effect.
研究了腺苷在异丙肾上腺素β-肾上腺素能刺激期间对单个分离的豚鼠心房肌细胞动作电位持续时间（APD）的调节作用。采用紧密封接全细胞膜片钳技术测量膜电位和离子电流。腺苷（10μM）拮抗异丙肾上腺素（20 nM）刺激的L型钙内向电流（ICa）。在存在异丙肾上腺素的情况下，腺苷（10μM）还增加了钳制电流和晚期外向电流。异丙肾上腺素（20 nM）在0 mV水平而非90%复极化水平导致心房动作电位显著延长。在存在异丙肾上腺素的情况下，腺苷剂量依赖性地缩短心房动作电位。有或无异丙肾上腺素（20 nM）时腺苷在0 mV的EC50值和最大缩短动作电位持续时间分别为3.0对2.2μM和42.9对30.4 ms。总之，在豚鼠心房肌细胞中，在异丙肾上腺素β-肾上腺素能刺激期间，腺苷引发特异性K+外向电流，并同时减弱异丙肾上腺素刺激的ICa。这些现象可能解释了有无异丙肾上腺素作用时腺苷对心房动作电位的调节。
