Mercury exchanges and toxicity in the crystalline lens in vitro

Mercury, (Hg2+, using 203Hg2+ as a tracer) was accumulated by the rabbit lens in vitro in a concentration-dependent manner. Saturation levels for the metal ion were greater at higher external concentrations of Hg2+ and exceeded those in the bathing media. Autoradiographic examination showed that the 203Hg was concentrated in the anterior epithelium and lens bow. Release of accumulated 203Hg was enhanced by external Hg2+ and dithiothreitol but was reduced by lanthanum (La3+). Lanthanum also increased net accumulation of Hg2+. The Hg2+ (10(-4) M for 24 h) appeared to be toxic as shown by excessive accumulation of sodium and loss of potassium by the lens in vitro. Mercuric ions appear to leave and enter the lens by diffusion, a process which may involve anionic pathways on its anterior surface where it is principally bound in the anterior epithelial cells.