RESUMEN
AIM: To study the effects of osthole (Ost) on the isolated guinea pig atria and the relationship between Ost effect and Ca2+. METHODS: Contractions of left atria were induced by electric stimulations. The contractile amplitude of left atria pre- and post-treated with Ost was measured according to the cumulative concentration method, the drug being added at 15 min intervals, the pA2 or pD2' were calculated. It were measured that the effects of Ost to the positive staircase and to the post-rest potential enhancement. The contractile responses were recorded via an auto-equiolibration recording instrument. RESULTS: Ost 10-300 mumol.L-1 and Ver 0.1-30 mumol.L-1 decreased the contractile force and inhibited the isoprenaline-induced restoration of contractile response in the left atria rendered inexcitable by KCl 25 mmol.L-1. Ost and Ver antagonized the CaCl2- and isoprenaline-induced positive inotropic response noncompetively, the pD2' values to Ost were 4.41 +/- 0.13 and 4.90 +/- 0.15, to Ver were 6.53 +/- 0.22 and 6.91 +/- 0.17, respectively. Both of them inhibited the contraction of the left atrium and reversed the frequency-contraction response from positive to negative staircase in the higher dosage (500 and 1 mumol.L-1), but they showed only slight inhibitory effect on post-rest potentiation. CONCLUSION: Ost was similar to, but much less potent than Ver in inhibiting the isolated guinea pig atria.
Asunto(s)
Bloqueadores de los Canales de Calcio/farmacología , Cumarinas/farmacología , Contracción Miocárdica/efectos de los fármacos , Animales , Cloruro de Calcio/antagonistas & inhibidores , Cumarinas/aislamiento & purificación , Depresión Química , Cobayas , Atrios Cardíacos/efectos de los fármacos , Técnicas In Vitro , Isoproterenol/antagonistas & inhibidores , Masculino , Plantas Medicinales/química , Verapamilo/farmacologíaRESUMEN
In recent years, it is believed by some scholars that the injury of myocardial ischemic reperfusion is correlated to the thromboxane A2 (TXA2) released by platelets. In order to explore that whether the myocardial and hemangio-endothelial cells participate in the TXA2 production during the process of reperfusion, the modified Langendorff method was used to establish the model of reperfusing the isolated rat heart. On the other hand, this experiment was also intended to observe the effect of ligustrazine on the injury of myocardial ischemic reperfusion. The results revealed that the level of thromboxane B2 (metabolite of TXA2) and lactic dehydrogenase (LDH) in coronary sinus reflux fluid increased during the process of reperfusion, while the level of 6-keto-PGF1 alpha in the same fluid relatively decreased (P < 0.05). The ratio of TXB2/6-keto-PGF1 alpha was raised. The ligustrazine inhibited the release of TXB2 and LDH, but promoted the production of 6-keto-PGF1 alpha (P < 0.05). The results also proved that the myocardial and hemangio-endothelial cells could synthesize TXA2, and the amount of TXA2 released increased during the reperfusion of ischemic myocardium, which was likely to be the major factor of the injury of ischemic myocardial reperfusion. Ligustrazine plays an important role in protecting the myocardium.