Cadmium turnover in the hemocytes of Mercenaria mercenaria (L.) in relation to hemocyte turnover

The turnover of cadmium (Cd) in the hemocytes of the quahog Mercenaria merc enaria L. was investigated using Cd-109 radiolabeling, and compared to the rate of hemocyte turnover as estimated following [H-3]thymidine incorporati on. Quahogs were injected with 5 mu l of 0.8 mu M Cd-109, and the hemocytes sampled over a 60-day depuration period. Additional organisms were injecte d with 15 mu l of 4.7 mu M [H-3]thymidine and radioactivity monitored over a 60-day period. Assuming that the loss of H-3 from the hemocytes during th e first 27 days of the experiment is due to hemocyte turnover, results indi cate that Cd turnover rate (t(0.5) = 25.3 +/- 6.3 days) was similar to hemo cyte turnover rate (t(0.5) = 28.5 +/- 14.3 days). This suggests that hemocy tes retain Cd internally throughout their circulatory lifespan. (C) 1999 El sevier Science Inc. All rights reserved.