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PubMed1989

Investigation of correlation between physiochemical properties of metals and their toxicity to the water flea Daphnia magna Straus.

Twenty-three metal ions were tested and ranked in terms of decrease in immobilization (EC50) of Daphnia magna Straus. The 48-hr EC50 values (mg/liter) of metal ions were Hg2+, 0.0052; Ag1+, 0.01; Cu2+, 0.093; Zn2+, 0.56; Co2+, 1.49; Cr6+, 1.79; Cd2+, 1.88; Be2+, 2.82; Pb2+, 3.61; As3+, 6.23; Fe2+, 7.20; Ni2+, 7.29; Mn2+, 8.28; Sn2+, 21.56; Ba2+, 32.00; Al3+, 59.60; W6+, 89.39; Sr2+, 94.00; K1+, 141.46; Mg2+, 343.56; Na1+, 420.60; and Sb3+, 423.45. The 48-hr EC50 values of 23 metal ions were transformed to their corresponding negative logarithms of molarity (as pM). Correlation coefficients (r) for more than 35 physiochemical properties of metals or metal ions and acute toxicity values (as pM) were examined by linear regression analysis. The negative logarithm of the solubility product constant of metal sulfide (pKsp), equilibrium constants of amino acids and of EDTA, nucleotide base, electronegativity, electrode potential, melting point, thermal properties of metals, and other physiochemical parameters were significantly correlated with toxicity for D. magna. The order of toxicity of metal ions has been presented and discussed. Correlation between toxicity and physiochemical properties of inorganic substances may be useful in predicting toxicity to various biologically important organisms.

Animals↗
PubMed2004

Lactose causes heart arrhythmia in the water flea Daphnia pulex.

The cladoceran Daphnia pulex is well established as a model for ecotoxicology. Here, we show that D. pulex is also useful for investigating the effects of toxins on the heart in situ and the toxic effects in lactose intolerance. The mean heart rate at 10 degrees C was 195.9+/-27.0 beats/min (n=276, range 89.2-249.2, >80% 170-230 beats/min). D. pulex heart responded to caffeine, isoproteronol, adrenaline, propranolol and carbachol in the bathing medium. Lactose (50-200 mM) inhibited the heart rate by 30-100% (K(1/2)=60 mM) and generated severe arrhythmia within 60 min. These effects were fully reversible by 3-4 h. Sucrose (100-200 mM) also inhibited the heart rate, but glucose (100-200 mM) and galactose (100-200 mM) had no effect, suggesting that the inhibition by lactose or sucrose was not simply an osmotic effect. The potent antibiotic ampicillin did not prevent the lactose inhibition, and two diols known to be generated by bacteria under anaerobic conditions were also without effect. The lack of effect of l-ribose (2 mM), a potent inhibitor of beta-galactosidase, supported the hypothesis that lactose and other disaccharides may affect directly ion channels in the heart. The results show that D. pulex is a novel model system for studying effects of agonists and toxins on cell signalling and ion channels in situ.

Ampicillin↗