delta-crystallin synthesis and vacuole formation during induced opacification of cultured embryonic chick lenses.

Previous experiments have shown that embryonic chick lenses cultured either without their vitreous bodies or with their vitreous bodies in the presence ofouabain alter their intracellular concentrations of sodium and potassium, change their ratio of synthesis of 8-crystallin polypeptides, and develop opacities in cortical or epithelial regions, respectively. In the present investigation b-crystallin synthesis was examined electrophoretically in the epithelial, cortical fiber, and nuclear fiber regions of the cultured lenses. The intercellular space was estimated by determining H-inulin uptake, and lens structure was visualized by light and electron microscopy. The results showed that the alteration in the ratio of b-crystallin synthesis occurred in both the clear and cloudy regions of the cultured lenses, suggesting that this change in protein synthesis does not cause the opacities. Moreover, experiments with cycloheximide revealed that inhibition of protein synthesis neither induced nor prevented the development of opacities in lenses lacking the vitreous body or treated with ouabain. Intercellular and intracellular vacuoles were directly associated with the opaque regions of these lenses, suggesting a causal basis for the opacities. Ouabain-treated lenses with attached vitreous bodies had only intracellular vacuoles, rather than a combination of intercellular and intracellular vacuoles, which is consistent with the possibility that the intercellular vacuoles are caused by excretion of fluid from the hydropic cells.