CALCIUM AND CADMIUM FLUXES ACROSS THE GILLS OF THE SHORE CRAB, CARCINUS-MAENAS

Fluxes of Ca-45 and Cd-109 across isolated, perfused Carcinus maenas gills and across gills in vivo were studied. The effects of lanthanum (a calcium channel blocker), KCN (a cytochrome oxidase inhibitor) and chlorpromazine (a Ca2+ ATPase blocker) were assessed. Calcium fluxes from 15 parts per thousand seawater in isolated perfused gills and in vivo gills were 1.9 and 2.2 mu moles Ca2+ g(-1) wet wt gill h(-1), respectively. Apical exposure to lanthanum inhibited calcium fluxes across perfused gills, whereas basolateral exposure to KCN and chlorpromazine did not inhibit calcium transport. Cadmium fluxes from 5 mu M Cd2+ in the seawater in isolated perfused gills and in vivo gills were approximately 0.7 and 0.5 nmoles Cd2+ g(-1) wet wt gill h(-1), respectively. In vivo exposure to lanthanum in seawater reduced cadmium accumulation from water in gills and carapace of C. maenas, whereas accumulation in midgut gland and muscle was not affected. In a preliminary experiment (apical) lanthanum did not inhibit Cd2+ influx across perfused gills. The mechanisms for calcium and cadmium transport in gills are discussed.