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 (Ca) concentration (0.1-10 mM Ca) as well as the Ca channel blockers lanthanum 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 inhibited by from 46 to 88%, respectively. A simple theoretical model of Cd-Ca competition for uptake sites fitted our observations well. Cadmium accumulation was significantly inhibited in a concentration-dependent manner by both 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.