Effects of total flavones of Hippophae rhamnoides L on cultured rat heart cells and on cAMP level and adenylate cyclase in myocardium

When total flavones of Hippophae rhamnoides L (TFH) 100 ug/ml were added to the medium. the spontaneous arrhythmias of the cell clusters disappeared in 14/19 experiments. TFH 100 ug/ml significantly counteracted the positive chronotropic effects of CaC12 and isoproterenol. with the maximal response being markedly decreased in the cultured rat heart cells. TFH 100 ug/ml reduced the level of cAMP in both ischemic and nonischemic myocardium in the isolated perfused rat heart. TFH 100 and 400 ug/ml inhibited adenylate cyclase of the rat ventricular myocardium. These results suggest that the antiarrhythmic effects of TFH are exerted on the heart cells directly. and that the calcium antagonizing action and inhibition of adenylate cyclase with a reduction in the cAMP level may be an important mechanism related to the antiarrhythmic effects.