Gomez Llambi H, Taquini C M, Mazzadi A, Gallo A, Fontan M, Taquini A C
Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Hypertension. 1990 Feb;15(2 Suppl):I51-4. doi: 10.1161/01.hyp.15.2_suppl.i51.
Studies in two-kidney--one clip hypertensive rats have demonstrated that long-term treatment with enalapril induced regression of cardiac hypertrophy, but the cardiac contractile response to beta-adrenergic stimulation remained depressed. In the present study, we evaluate the contractile response to beta-adrenergic stimulation of isolated papillary muscle in normal rats with isoproterenol (10(-11) M to 10(-4) M) in the presence of enalaprilic acid (10(-6) M or 10(-4) M) or enalaprilic acid (10(-4) M) and angiotensin II (10(-6) M). Myocardial contractility was characterized by maximal developed tension and maximal rate of rise of tension (+T), and the relaxant effect of isoproterenol by the ratio of (+T), and the maximal velocity of relaxation (-T)(+T/-T ratio). The rest tension (g/mm2) and the cross-sectional area (mm2) were similar in all the muscles studied. Enalaprilic acid (either 10(-6) M or 10(-4) M) in the bath did not induce any change in contractile and relaxation parameters. The increment in +T and -T (expressed as percentage) in response to cumulative doses of isoproterenol (10(-11) M to 10(-4) M) was significantly depressed in the presence of enalaprilic acid (10(-4) M) when compared with control hearts in which only vehicle was added before isoproterenol (p less than 0.05). The addition of angiotensin II after enalaprilic acid (10(-4) M) did not normalize the response in +T and -T. Enalaprilic acid diminishes the contractile response of the papillary muscle to beta-adrenergic stimulation. The inhibition of the local angiotensin II does not seem to be involved in this result.
对两肾一夹型高血压大鼠的研究表明，依那普利长期治疗可使心脏肥大消退，但心脏对β-肾上腺素能刺激的收缩反应仍受抑制。在本研究中，我们评估了在依那普利酸（10⁻⁶ M或10⁻⁴ M）或依那普利酸（10⁻⁴ M）与血管紧张素II（10⁻⁶ M）存在的情况下，正常大鼠离体乳头肌对异丙肾上腺素（10⁻¹¹ M至10⁻⁴ M）的β-肾上腺素能刺激的收缩反应。心肌收缩力以最大张力发展和张力上升最大速率（+T）为特征，异丙肾上腺素的舒张作用以（+T）与最大舒张速度（-T）的比值（+T/-T比值）来表示。在所研究的所有肌肉中，静息张力（g/mm²）和横截面积（mm²）相似。浴槽中的依那普利酸（10⁻⁶ M或10⁻⁴ M）未引起收缩和舒张参数的任何变化。与仅在异丙肾上腺素前加入溶媒的对照心脏相比，在依那普利酸（10⁻⁴ M）存在时，对累积剂量异丙肾上腺素（10⁻¹¹ M至10⁻⁴ M）的反应中+T和-T的增加（以百分比表示）明显降低（p<0.05）。在依那普利酸（10⁻⁴ M）后加入血管紧张素II并未使+T和-T的反应恢复正常。依那普利酸降低了乳头肌对β-肾上腺素能刺激的收缩反应。局部血管紧张素II的抑制似乎与该结果无关。
