Cadmium uptake in gills of the mollusc Crassostrea virginica and inhibition by calcium channel blockers

Abstract

Cadmium uptake by excised gills of Crassostrea virginica occurred in a linear concentration-dependent manner in media containing up to 1.78 μM total cadmium, the highest concentration tested. Cadmium uptake was insensitive to sodium cyanide, anoxia, and ouabain, but was significantly inhibited ( p < 0.05) when gills were treated with 2,4-dinitrophenol, an uncoupler of oxidative phosphorylation. Cadmium uptake was also significantly inhibited by the calcium channel blockers nifedipine, a 1,4-dihydropyridine; diltiazem, a benzothiazepine; and verapamil, a phenalkylamine. These reagents are known to bind different sites in calcium channels. The findings represent strong evidence that cadmium entry into cells of gills of these marine molluscs occurs through calcium channels. However, since the same reagents inhibited calcium uptake to a much lesser extent in comparison with cadmium, it appears that cadmium uses only a subset of pathways available for calcium.