Böhm M, Brückner R, Meyer W, Nose M, Schmitz W, Scholz H, Starbatty J
Naunyn Schmiedebergs Arch Pharmacol. 1985 Nov;331(2-3):131-9. doi: 10.1007/BF00634229.
The effects of the adenosine agonists (-)-N6-phenylisopropyladenosine (PIA) and 5'-N-ethylcarboxamideadenosine (NECA) on force of contraction, adenylate cyclase activity and normal as well as slow action potentials were studied in guinea-pig isolated atrial (left auricles) and ventricular preparations (papillary muscles). In auricles PIA and NECA exerted concentration-dependent negative inotropic effects with similar potencies (mean EC50:0.05 mumol l-1 for PIA and 0.03 mumol l-1 for NECA). Similar results were obtained in the presence of isoprenaline. In papillary muscles PIA and NECA alone had no effect on force of contraction but produced negative inotropic effects in the presence of isoprenaline (mean EC50:0.19 mumol l-1 for PIA and 0.10 mumol l-1 for NECA). In both preparations, the negative inotropic effects of PIA and NECA in the presence of isoprenaline were antagonized by the adenosine receptor antagonist 8-phenyltheophylline. In both preparations, PIA and NECA did not affect adenylate cyclase activity, both in the absence and presence of isoprenaline. In auricles the negative inotropic effects of both nucleosides were accompanied by a shortening of the action potential. This effect was also observed in the presence of isoprenaline. In papillary muscles the adenosine analogs did not detectably alter the shape of the normal action potential. Ca2+-dependent slow action potentials elicited in potassium-depolarized preparations also remained unaltered in the presence of PIA or NECA alone. However, the isoprenaline-induced enhancement of the maximal rate of depolarization of slow action potentials was attenuated by PIA or NECA.(ABSTRACT TRUNCATED AT 250 WORDS)
在豚鼠离体心房（左心耳）和心室标本（乳头肌）中，研究了腺苷激动剂（-）-N6-苯异丙基腺苷（PIA）和5'-N-乙基甲酰胺腺苷（NECA）对收缩力、腺苷酸环化酶活性以及正常和慢动作电位的影响。在心房中，PIA和NECA产生浓度依赖性负性肌力作用，效力相似（PIA的平均EC50为0.05 μmol·L-1，NECA为0.03 μmol·L-1）。在异丙肾上腺素存在的情况下也得到了类似结果。在乳头肌中，单独的PIA和NECA对收缩力无影响，但在异丙肾上腺素存在时产生负性肌力作用（PIA的平均EC50为0.19 μmol·L-1，NECA为0.10 μmol·L-1）。在这两种标本中，腺苷受体拮抗剂8-苯基茶碱可拮抗异丙肾上腺素存在时PIA和NECA的负性肌力作用。在这两种标本中，无论有无异丙肾上腺素，PIA和NECA均不影响腺苷酸环化酶活性。在心房中，两种核苷的负性肌力作用均伴有动作电位缩短。在异丙肾上腺素存在时也观察到了这种效应。在乳头肌中，腺苷类似物未检测到对正常动作电位形状的明显改变。在钾去极化标本中诱发的钙依赖性慢动作电位，在单独存在PIA或NECA时也保持不变。然而，PIA或NECA可减弱异丙肾上腺素诱导的慢动作电位最大去极化速率的增强。（摘要截短至250字）
