The cardiotoxic action of the pyrethroid insecticide deltamethrin, the azole fungicide prochloraz, and their synergy on the semi-isolated heart of the bee Apis mellifera macedonica

The contraction of the isolated heart of the bee in physiological solution can be monitored for hours, making this preparation suitable for the invest igation of the cardiotoxic action of certain compounds. The results of this study have shown that exposure of the semi-isolated heart of the bee to 1, 0.1, and 0.01 muM deltamethrin causes a temporal increase in the frequency and the force of spontaneously generated contractions, which is followed b y a decrease in both parameters. The decrease is dose dependent. The action of deltamethrin was not reversible. The fungicide prochloraz applied at th e same concentration levels as deltamethrin has an immediate chronotropic a nd inotropic effect on the semi-isolated heart of the bee, but its effects are more intense than those caused by deltamethrin. Comparison of the dose- response curves clearly shows that prochloraz is more cardiotoxic than delt amethrin. When prochloraz and deltamethrin are combined there is an increas e of over 100 times in the cardiotoxicity of deltamethrin and an increase o f 10 limes in the toxicity of prochloraz. Our suggestion is that this syner gistic action could be caused by the action of the two compounds on the sam e target site, which in the heart of the bee may be gap junctional intercel lular communication a vital physiological mechanism for the functioning of the heart in both vertebrates and invertebrates. (C) 2001 Academic Press.