The evaluation of the cardiovascular toxicity of surfactants contained in agricultural chemicals

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A herbicide Basta (BST), containing glufosinate ammonium (GLA), an anionic surfactant (AES), and a glycol (GLY), causes circulatory failre with a decrease in vasculr resistance in human oral poisoning. We tried to elucidate the exact component that is mostly responsible for the cardiovascular effects of this herbicide formulation. In isolated right atria beating spontaneously in Krebs-Ringer's solusion, BST and AES produced negative chronotropic responses in a concentration dependent manner. In electrically driven isolatred left atria, BST and AES caused positive intoropic responses concentration dependently but negative inotropic responses at extremely high concentrations. In aortic segments, BST and AES produced significant vasodilative effects when the aorta was precontracted with phenylephrine. In anesthetized rats, low doses of BST and AES produced a decrease in blood pressure with a slight increase in heart rate, which was suspected to the baroreflex induced by the decrease in blood pressure. At an extremely high dose, BST and AES produced a decrease in blood pressure with a marked decrease in heart rate. The changes induced by BST and AES both in in vitro and in vivo experiments occrred to a similar degree. On the other hand, GLA and GLY did not produce sigmificant effects in either in vitro or in vivo experiments. We conclude that the direct cariovasular effects of BST are mostly caused by the surfactant AES through its vasodilative effects plus cardiostimulative effects at low doses and cardiosuppressive effects at high doses.