Doggrell S A
Department of Pharmacology, School of Medicine, University of Auckland, New Zealand.
J Pharm Pharmacol. 1992 Dec;44(12):1001-6. doi: 10.1111/j.2042-7158.1992.tb07082.x.
Differing effects of labetalol and dilevalol on cardiovascular preparations have been reported. I have studied the effects of labetalol and dilevalol on the contractile responses of the rat and guinea-pig left atria and rat portal vein. On the guinea-pig left atria low concentrations of labetalol (> or = 10(-8) M) and of dilevalol (> or = 10(-7) M) inhibited to a small extent the responses to electrical cardiac stimulation, which is indicative of membrane stabilizing activity. Labetalol (> or = 3 x 10(-8) M) and dilevalol (> or = 10(-8) M) caused surmountable antagonism of the isoprenaline responses of the atria and the pA2 values were 8.60 and 8.98 at the beta 1-adrenoceptors of the rat left atria and 7.90 and 8.31, respectively, on the guinea-pig left atria which has functional beta 1- and beta 2-adrenoceptors. Labetalol and dilevalol (both at > or = 10(-7) M) attenuated the spontaneous contractile activity of the rat portal vein and the attenuation to labetalol at 10(-6) M was abolished by ICI 118,551 which illustrates that the labetalol-induced attenuation is beta 2-adrenoceptor mediated. The isoprenaline attenuation responses of the portal vein were inhibited by labetalol and dilevalol (both at > or = 10(-7) M) and the pA2 value for the labetalol at beta 2-adrenoceptors was 7.59. It is concluded that labetalol and dilevalol are beta 1-adrenoceptor selective antagonists.
已有报道称拉贝洛尔和地来洛尔对心血管制剂有不同作用。我研究了拉贝洛尔和地来洛尔对大鼠和豚鼠左心房以及大鼠门静脉收缩反应的影响。在豚鼠左心房，低浓度的拉贝洛尔（≥10⁻⁸ M）和地来洛尔（≥10⁻⁷ M）对心脏电刺激反应有轻微抑制，这表明有膜稳定活性。拉贝洛尔（≥3×10⁻⁸ M）和地来洛尔（≥10⁻⁸ M）对心房异丙肾上腺素反应产生可克服的拮抗作用，在大鼠左心房β₁ - 肾上腺素受体处的pA₂值分别为8.60和8.98，在具有功能性β₁和β₂ - 肾上腺素受体的豚鼠左心房处分别为7.90和8.31。拉贝洛尔和地来洛尔（均≥10⁻⁷ M）减弱大鼠门静脉的自发收缩活性，ICI 118,551可消除10⁻⁶ M拉贝洛尔引起的减弱作用，这说明拉贝洛尔引起的减弱作用是由β₂ - 肾上腺素受体介导的。拉贝洛尔和地来洛尔（均≥10⁻⁷ M）抑制门静脉对异丙肾上腺素的减弱反应，拉贝洛尔在β₂ - 肾上腺素受体处的pA₂值为7.59。结论是拉贝洛尔和地来洛尔是β₁ - 肾上腺素受体选择性拮抗剂。
