Ca++-induced cataract.

Cataracts in cultured rabbit lenses were produced by elevation of internal calcium. Experimental procedures were successful in increasing levels of total and bound Ca++, often without significant changes in sodium, potassium, or water content. Although the excess in calcium was predominantly associated with water-soluble proteins and was freely diffusible, a significant amount was bound to membranes and cytosol water-insoluble proteins. Thus, in lenses with a 10-fold increase in total Ca++, the bound Ca++ increased twofold, nearly 35% of which remained fixed to water-insoluble and membrane proteins after exhaustive (72 hr) dialysis. In contrast, over 95% of the Ca++ in water-soluble protein fractions was removed by dialysis.