Effects of the group IIB metals (Cd, Zn and Hg) on the permeability of the crystalline lens of the toad (Bufo marinus)

1. 1. Cd, Zn, Hg and methyl mercury chloride (on anterior, not posterior) decrease the potential difference and short-circuit current across the lens of the toad. 2. 2. When translenticular Na transport was abolished, these metals were still effective. When Na was removed from the anterior, the effects of Cd and Zn were abolished, whereas Hg and CH₃ Hg continued to act. Lenses in vitro accumulated Na and lost K in the presence of Cd and Hg but Zn or CH₃Hg had no effect. 3. 3. O₂ consumption in vitro was reduced by Zn, Hg and CH₃Hg, but not Cd. In the absence of Na, Hg and CH₃Hg still decreased O₂ consumption indicating a general toxic effect. 4. 4. The group IIB metal ions alter the electrical parameters and permeability of the crystalline lens but they act in different ways which reflects their varied chemical properties.