Effects of bufadienolides and some kinds of cardiotonics on guinea pig hearts

Abstract

Effects of bufadienolides such as bufalin (BF) and cinobufagin (CB), the main components of Senso (Ch'an Su), on myocardial Na+, K+-ATPase activity, the cardiotonic activity in vivo and the action potential of isolated guinea pig papillary muscle cells were compared with those of other cardiotonic drugs. 1) The rank order of potency for inhibition of myocardial Na+, K+-ATPase activity was BF >digoxin (DG) > digitoxin (DT) > telocinobufagin>gamabufotalin>cinobufotalin>CB>g-strophan-thin (GS) >digitoxigenin (DTG) >resibufogenin (RB) when compared at the 50% inhibitory concentration. 2) In isolated papillary muscle cells, CB shortened the action potential duration (APD)dose-dependently. The order of potency for shortening of APD was GS>CB>DTG≫DT. 3) In open-chest guinea pigs, intraduodenal administration of BF or CB increased the myocardial contractile force (MCF), but did not affect the heart rate. The order of potency for increase in MCF was as follows: methyldigoxin, proscillaridin>BF>CB>DG>Senso≫DT, DTG, RB. These results indicate that CB has a shortening effect on APD and an inhibitory effect on Na+, K+-ATPase activity along with its cardiotonic effect, like GS. © 1992, The Japanese Pharmacological Society. All rights reserved.