Osnes J B, Refsum H, Skomedal T, Oye I
Acta Pharmacol Toxicol (Copenh). 1978 Apr;42(4):235-47. doi: 10.1111/j.1600-0773.1978.tb02195.x.
If beta- and alpha-adrenergic inotropic effects are cyclic AMP dependent and cyclic AMP independent, respectively, they may be qualitatively different. The inotropic effects of beta-receptor stimulation (isoprenaline) and alpha-receptor stimulation (phenylephrine combined with propranolol) were characterized in isolated perfused rat hearts, rat atria and rat papillary muscles. The beta-effect reached its maximum before the alpha-effect. The alpha-effect followed a three-phasic time-course indicating both stimulatory and inhibitory components. The aortic pressure wave (perfused heart) indicated a shorter contraction phase after beta-stimulation than after alpha-stimulation. The time to peak tension (atrium, papillary muscle) was relatively shorter after isoprenaline than after alpha-stimulation, which tended to prolong it. The contraction-relaxation cycles (atrium, papillary muscle) were examined by recording the isometric tension (T), its first (T') and second (T'') deri derivatives. alpha and beta-stimulation both increased Tmax, T'max (maximal rate of tension rise), T'min (maximal rate of tension decline) and T''min (maximal rate of transition from rise to decline of tension). Isoprenaline increased T'min (papillary muscle) and T''min (atrium, papillary muscle) relatively more than did alpha-stimulation, i.e. the relaxing processes were activated relatively more by beta-stimulation. The results indicate different mechanisms for the two adrenergic inotropic effects. The relatively larger activation of relaxation by beta-stimulation is assumed to be caused by clic AMP.
如果β-肾上腺素能正性肌力作用和α-肾上腺素能正性肌力作用分别依赖环磷酸腺苷（cAMP）和不依赖环磷酸腺苷，那么它们在性质上可能有所不同。在离体灌注大鼠心脏、大鼠心房和大鼠乳头肌中，对β受体刺激（异丙肾上腺素）和α受体刺激（去氧肾上腺素联合普萘洛尔）的正性肌力作用进行了表征。β效应在α效应之前达到最大值。α效应呈现三相时间进程，表明同时存在刺激和抑制成分。主动脉压力波（灌注心脏）显示，β刺激后的收缩期比α刺激后的短。异丙肾上腺素作用后，达到峰值张力的时间（心房、乳头肌）比α刺激后相对较短，α刺激往往会延长该时间。通过记录等长张力（T）及其一阶导数（T'）和二阶导数（T''）来检查收缩-舒张周期（心房、乳头肌）。α和β刺激均增加了Tmax、T'max（张力上升的最大速率）、T'min（张力下降的最大速率）和T''min（张力从上升到下降的最大转换速率）。与α刺激相比，异丙肾上腺素相对更能增加T'min（乳头肌）和T''min（心房、乳头肌），即β刺激相对更能激活舒张过程。结果表明两种肾上腺素能正性肌力作用的机制不同。β刺激相对更大程度地激活舒张被认为是由环磷酸腺苷（cAMP）引起的。
