Li W, Zhang Y, Wang X L
Department of Pharmacology, Chinese Academy of Medical Sciences, Beijing, China.
Zhongguo Yao Li Xue Bao. 1997 May;18(3):237-40.
To study inotropic and chronotropic effects mediated by alpha 1A- and alpha 1B-adrenoceptors after 5-d propranolol (Pro) treatment.
The positive inotropic and chronotropic effects mediated by alpha 1A and alpha 1B subtypes were determined on isolated left ventricular papillary muscles and right atrium in Pro- and NaCl-treated rats.
The basic contractility of papillary muscles induced by phenylephrine (Phe) was 90 +/- 18 mg in Pro-treated rats and 53 +/- 17 mg in control group (P < 0.05). The increment on force of contraction was 20 +/- 12 mg in Pro-pretreated rats and 5 +/- 5 mg in NaCl-treated rats (P < 0.05). After preincubated with chloroethylclonidine, the increment on force of contraction was reduced in Pro-treated rats, but was not much changed in control group. Phe in presence of 5-methylurapidil induced positive inotropic effect with 13 +/- 5 mg in Pro-treated group, but not in NaCl-treated rats. Under the normal and the inhibited cardiac state, the maximal increment in beat rate mediated by alpha 1B showed no difference between the Pro-treated and NaCl-treated rats.
After chronic treatment of Pro, alpha 1-adrenoceptor-mediated positive inotropic effect in rat heart was improved, which was mainly induced by stimulation of alpha 1B when beta-adrenoceptors were blocked.
研究普萘洛尔（Pro）治疗5天后，α1A和α1B肾上腺素能受体介导的变力性和变时性效应。
在Pro处理组和NaCl处理组大鼠的离体左心室乳头肌和右心房上，测定α1A和α1B亚型介导的正性变力性和变时性效应。
苯肾上腺素（Phe）诱导的Pro处理组大鼠乳头肌基础收缩力为90±18mg，对照组为53±17mg（P<0.05）。Pro预处理组大鼠收缩力增加20±12mg，NaCl处理组为5±5mg（P<0.05）。用氯乙可乐定预孵育后，Pro处理组大鼠收缩力增加幅度降低，而对照组变化不大。在5-甲基尿嘧啶存在下，Phe在Pro处理组诱导的正性变力性效应为13±5mg，而NaCl处理组大鼠未出现该效应。在正常和心脏抑制状态下，α1B介导的Pro处理组和NaCl处理组大鼠心率最大增加幅度无差异。
长期使用Pro后，大鼠心脏中α1肾上腺素能受体介导的正性变力性效应增强，这主要是在β肾上腺素能受体被阻断时由α1B的刺激引起的。
