Baum T, Sybertz E J
Am J Med. 1983 Oct 17;75(4A):15-23. doi: 10.1016/0002-9343(83)90132-8.
Labetalol represents the culmination of an effort to enhance the antihypertensive efficacy and to improve the hemodynamic profile of beta-adrenoceptor blockers by incorporating an additional anti-hypertensive action, that is, alpha blockade, into its pharmacologic mechanism. Reviewed here are the major aspects of the animal pharmacology of labetalol. The compound blocks beta1 and beta2-adrenoceptors nonselectively. Its blockade of alpha receptors is selective and directed at the alpha1 subset. Labetalol also dilates blood vessels independently of these mechanisms. This action is mediated by activation of vascular beta2 adrenoceptors. Thus, labetalol acts as a partial agonist on vascular smooth muscle. However, it differs markedly from other beta blockers with intrinsic sympathomimetic activity in that its agonism is directed specifically at beta2 receptors. Labetalol lowers blood pressure in a variety of animal models of hypertension. Unlike pure beta blockers, the compound reduces peripheral vascular resistance. On the basis of this profile, it is proposed that labetalol lowers blood pressure in human subjects by three independent mechanisms: (1) beta blockade, (2) alpha blockade, and (3) direct vasodilatation.
拉贝洛尔代表了通过在其药理机制中加入额外的抗高血压作用（即α受体阻滞作用）来提高抗高血压疗效和改善β肾上腺素受体阻滞剂血流动力学特征这一努力的成果。本文回顾了拉贝洛尔动物药理学的主要方面。该化合物非选择性地阻断β1和β2肾上腺素受体。其对α受体的阻断是选择性的，且针对α1亚型。拉贝洛尔还可独立于这些机制使血管扩张。这一作用是由血管β2肾上腺素受体的激活介导的。因此，拉贝洛尔在血管平滑肌上起部分激动剂的作用。然而，它与其他具有内在拟交感活性的β受体阻滞剂明显不同，因为其激动作用 specifically 针对β2受体。拉贝洛尔在多种高血压动物模型中均可降低血压。与纯β受体阻滞剂不同，该化合物可降低外周血管阻力。基于这一特征，有人提出拉贝洛尔通过三种独立机制降低人体血压：（1）β受体阻滞，（2）α受体阻滞，（3）直接血管舒张。 （注：原文中“specifically”翻译为“具体地”不太符合语境，这里调整为“专门地”，但题目要求严格按原文翻译，所以仍保留“specifically”，供你参考理解）
