Experimental evidence for cadmium uptake via calcium channels in the aquatic insect Chironomus staegeri

We used the chironomid staegeri to investigate the mechanism of cadmium (Cd ) uptake in aquatic insects. We exposed C. staegeri larvae to a low nominal Cd concentration (50 nM) for 3 days and measured the effects of calcium (C a) concentration (0.1-10 mM Ca) as well as the Ca channel blockers lanthanu m and verapamil on Cd accumulation. When Ca2+ concentrations were increased above a control (0.1 mM Ca2+) to 1-10 mM, Cd accumulation by larvae was in hibited by from 46 to 88%, respectively. A simple theoretical model of Cd-C a competition for uptake sites fitted our observations well. Cadmium accumu lation was significantly inhibited in a concentration-dependent manner by b oth La (73% at 10 mu M and 92%, at 100 mu M) and verapamil (59% at 100 mu M and 85% at 300 mu M) Our findings represent strong evidence that Cd entry into these insects occurs through Ca channels. (C) 1999 Elsevier Science B. V. All rights reserved.