Application of enriched stable isotope technique to the study of copperbioavailability in Daphnia magna
Wenhong Fan , Chenguang Wu , Chunmei Zhao , Tao Yu , Yuan Zhang
DOI:
Received July 26, 2010,Revised December 12, 2010, Accepted , Available online
Volume 23,2011,Pages 831-836
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The biokinetics of Cu in Daphnia magna, including dissolved uptake, assimilation and e ux, has been determined using a gamma
67Cu radiotracer methodology. However, this gamma emitting radioisotope is not readily available due to its very short half-life. In the
present study, we employed a stable isotope tracer (65Cu) to determine the Cu biokinetics and compared our results to those determined
using 67Cu. The dissolved uptake rate constant of 65Cu was 3.36 L/(g day), which is higher than that of 67Cu (1.32 L/(g day)). With
increasing food concentrations from 2 104 to 1 105 cells/mL, the Cu assimilation e ciency (AE) decreased from 46% to 11%,
compared to a decrease from 27% to 16% when determined using 67Cu. The e ux of Cu from Daphnia magna was quantified following
both dissolved and dietary uptake. The e ux of waterborne Cu was comparable to that of dietborne Cu and the e ux rate constant
(0.32–0.52 day??1) was higher than that determined by 67Cu (0.19–0.20 day??1). By considering di erent water properties and handling
procedure between the two experiments, we believe that these di erences are reasonable. Overall, this study demonstrated that the
enriched stable isotope tracer technique is a powerful tool to investigate metal bioavailability and maybe a good alternative to radioactive
measurements.
