The influence of calcium on protein synthesis in the rabbit lens.

Biosynthesis of lens proteins, as assessed by the incorporation of 14C-histidine, was investigated in young rabbit lenses cultured under conditions designed to specifically elevate lens calcium. While such lenses rarely were obtained without small degrees of Na/K imbalances, experiments with ouabain-treated lenses over comparable times indicated that changes solely in Na/K levels did not alter synthesis of lens crystallins. On the other hand, with far smaller changes in Na/K levels, excess calcium accumulation obtained by exposing lenses to A23187 or high levels of medium calcium invariably led to diminished synthesis of lens proteins. An increase in lens calcium from 0.2 mM to 0.6 mM led to a small but statistically insignificant decline in protein synthesis, while an increase to 1.4 mM or 1.9 mM resulted in a decline to values 50% and 11%, respectively, of the control. The results indicate that calcium may be important in influencing protein synthesis in the lens.