Heavy metal action on transintegumentary absorption of glycine in two annelid species

Abstract

Absorption of 14C-glycine from ambient sea water across the body surface of the oligochaete Enchytraeus albidus Henle was, after 6 h preincubation, significantly reduced in the presence of 0.1 to 0.15 ppm mercury, 0.25 ppm copper, 1.5 ppm silver, and 2 ppm cadmium. Addition of heavy metal salts reduced maximum uptake rates (Vmax), without affecting transport constants (Kt). Influx of 14C-glycine remained unchanged in the presence of up to 10 ppm aluminium, chromium, iron, lead, molybdenum, vanadium, and zinc. Effects of up to 150 ppm nickel, manganese, cobalt and selenium were negligible. Inhibition of glycine absorption by mercury and cadmium in the polychaete Nereis diversicolor Muller is almost identical with results presented for E. albidus. Transintegumentary solute absorption in soft-bodied marine invertebrates obviously represents a suitable biological function for studies on heavy metal toxicity. The close relationship between rates of heavy metal absorption, inhibition of transintegumentary glycine uptake, and acute toxicity is discussed.