洛土辛对离体心肌的正性肌力作用及机制

Positive Inotropic Effect of Lotusine on Isolated My ocardium and Its Mechanism

洛土辛 （Ｌｏｔ） 系莲子心中的一种新型生物碱单体。Ｌｏｔ、氨力农 （Ａｍ ） 和罂粟碱 （Ｐａ） 剂量依赖性地增加离体心肌的收缩力且Ｌｏｔ的作用强于Ａｍ 和Ｐａ。Ｌｏｔ ３０ μｍ ｏｌ／Ｌ分别使豚鼠、大鼠、家兔左房和豚鼠、大鼠、猫乳头状肌收缩力增加４５％ 、５５％ 、５１％ 和５６％ 、５３％ 、４７％ 。在利血平化豚鼠， Ｌｏｔ的正性肌力作用被削弱， 而Ｐａ的作用不但被削弱甚至转为负性肌力作用。Ｌｏｔ略使异丙肾上腺素的量效曲线左移并增强Ａｍ 、Ｐａ 及小檗碱的正性肌力作用。Ｌｏｔ还明显增加离体工作心脏的左心室压 （ＬＶＰ）、左心室收缩速率 （＋ ｄｐ／ｄｔ）。

Lotusine (Lot) is an alkaloid extracted from the green seed em bryo of Nelubonucifera Gaertn. Lot, Am rinone (Am ), Paparvine (Pa) 1～100 μm ol/L could dose-dependently increase the contractile force (Fc) ofisolated leftatria or papillary m uscles ofratand guinea pig and the potency ofLot w as significantly stronger than Am and Pap. The Fc of left atria of guinea pig, rat, rabbit and papillary m uscles ofguinea pig, rat, cat w ere increased by 45 % , 55 % , 51 % and 56 % , 53 % , 47 % respectively by Lot 30 μm ol/L. In guinea pig pretreated w ith reserpine, the positive inotropic effects ofLot and Pa on papillary m uscles w ere dim inished. Moreover, the effects of the latter w ere even overturned to negative inotropic effect. Lot slightly shifted the dose-response curve of isoprenaline to the left. But Lot did not affect the heart rate of right atria. Lot could potentiate the positive inotropic effects of Am , Pa and berberine. Moreover, it could significantly elevate the left ventricular pressure (LVP) and + dp/dt (m axim alvelocity ofleft ventricular pressure change) in guinea pig w orking heart. These results indicated that the m echanism of the inotropic effects of Lot on m yocardium m ay be related to the inhibition of phosphodiesterase Ⅲ.