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D600 and nifedipine produced a concentration-dependent reduction in mechanical responses to noradrenaline in rat portal vein, while sodium nitroprusside had no effect.
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In rat portal vein, D600 primarily inhibits calcium influx, nifedipine interferes with electromechanical coupling, and sodium nitroprusside has no effect on noradrenaline-induced activity.
1 The effects of methoxyverapamil (D600), nifedipine and sodium nitroprusside on noradrenaline-induced electrical and mechanical activity in rat portal vein have been examined. 2 D600 and nifedipine produced a concentration-dependent reduction in mechanical responses to noradrenaline whilst sodium nitroprusside had no effect. The effects of D600 and nifedipine were reversed by increasing the extracellular calcium concentration. 3 The mechano-inhibitory effects of D600 were accompanied by a marked reduction in electrical activity with some evidence of electromechanical uncoupling. 4 The mechano-inhibitory effects of nifedipine were associated with considerable electromechanical uncoupling. 5 It is concluded that in the concentrations used, D600 acts primarily by inhibiting calcium influx with some effect on electromechanical coupling whilst nifedipine interferes mainly with the coupling process. The inactivity of sodium nitroprusside suggests that the excitation-contraction coupling process in rat portal vein is relatively simple and further studies with this tissue seem indicated.
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JETLEY et al. (1980) studied this question. Methoxyverapamil (D600), nifedipine and sodium nitroprusside was evaluated on Noradrenaline-induced electrical and mechanical activity. D600 and nifedipine produced a concentration-dependent reduction in mechanical responses to noradrenaline in rat portal vein, while sodium nitroprusside had no effect.
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