Jahnel U, Kaufmann B, Rombusch M, Nawrath H
Pharmakologisches Institut, Universität Mainz, Federal Republic of Germany.
Naunyn Schmiedebergs Arch Pharmacol. 1992 Dec;346(6):665-72. doi: 10.1007/BF00168740.
The functional role of alpha-adrenoceptors was investigated in different parts of the rabbit heart. Phenylephrine (PE) caused a marked increase in force of contraction (Fc) and a prolongation of the action potential (AP) in preparations from the left atrium and the right ventricle. The response was less pronounced in the right atrium and in the left ventricle, whereas APs of spontaneously beating sinoatrial preparations remained completely unchanged. Phentolamine as well as the diesters phorbol 12,13 dibutyrate (PDBu) or 12-O-tetradecanoyl-phorbol-13-acetate (TPA) eliminated the effects of PE. The contribution of alpha-adrenoceptors to the effects of adrenaline (Adr) and noradrenaline (NA) on Fc was determined in preparations from the right ventricle. Phentolamine and the phorbol diesters reduced the effects of Adr and NA by about 30 to 60%; the remaining response was abolished by propranolol. It can be derived from our experiments that, in some parts of the rabbit heart, a considerable amount of the effects of Adr and NA is due to the stimulation of alpha-adrenoceptors. The present findings therefore support the view that, in the rabbit heart, the maximally effective drive of the heart requires the stimulation of both alpha- and beta-adrenoceptors. The inhibitory effects of phorbol diesters on the alpha-adrenoceptor-mediated response indicate that the activation of protein kinase C (PKC) specifically uncouples alpha-adrenoceptors from the effector system, whereas the response to beta-adrenoceptor stimulation remains unchanged.
研究了α-肾上腺素能受体在兔心脏不同部位的功能作用。去氧肾上腺素（PE）可使左心房和右心室标本的收缩力（Fc）显著增加，并使动作电位（AP）延长。右心房和左心室的反应则不太明显，而自发搏动的窦房结标本的动作电位保持完全不变。酚妥拉明以及佛波醇12,13 - 二丁酸酯（PDBu）或12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA）可消除PE的作用。在右心室标本中测定了α-肾上腺素能受体对肾上腺素（Adr）和去甲肾上腺素（NA）作用于Fc的贡献。酚妥拉明和佛波醇二酯可使Adr和NA的作用降低约30%至60%；其余反应可被普萘洛尔消除。从我们的实验可以得出，在兔心脏的某些部位，Adr和NA的相当一部分作用是由于α-肾上腺素能受体的刺激。因此，目前的研究结果支持这样一种观点，即在兔心脏中，心脏的最大有效驱动需要α-和β-肾上腺素能受体的刺激。佛波醇二酯对α-肾上腺素能受体介导反应的抑制作用表明，蛋白激酶C（PKC）的激活特异性地使α-肾上腺素能受体与效应器系统解偶联，而对β-肾上腺素能受体刺激的反应保持不变。
