The heart of Daphnia magna: Effects of four cardioactive drugs

Abstract

We used Daphnia magna bioassays to determine the LC50 and the effects on the heart of the cardioactive drugs ouabain, verapamil, metaproterenol and metoprolol. Distinctions were made between the pharmacological and toxicological effects of these drugs and the adequacy of physicochemical characteristics of its habitat (reconstituted water). Video microscopy and digital image processing were used to study the pharmacological effects on the heart. D. magna exhibited the expected sensitivity to the reference toxicant sodium dodecyl sulfate with a LC50 of 15.6±4.5 mg/l. All drugs were toxic with 48 h-LC50 of 2.03 mg/l ouabain, 7.04 mg/l verapamil, 32.45 mg/l metaproterenol and 76.21 mg/l metoprolol. Ouabain was the most toxic and caused a positive concentration-dependent inotropic effect. Verapamil caused positive chronotropic and inotropic effects, while metaproterenol showed positive concentration-dependent chronotropic effects at high concentrations (10 -3 and 10-4 M). Metoprolol induced a positive chronotropic effect at low concentrations (10-8, 10-7, 10-6 M) and a negative chronotropic effect at high concentration (10-4 M). Ouabain, metaproterenol and metoprolol in D. magna caused similar effects to those produced in mammals. In contrast, verapamil caused opposite effects. The results suggest the presence of Na+, K +-ATPase receptors to verapamil and of non-specific adrenergic receptors in heart of D. magna. © 2003 Elsevier Inc. All rights reserved.