Calcium-induced disruption of the lens cytoskeleton.

Ionic homeostasis is essential to lens clarity and the lens epithelium plays a large part in homeostasis, through vectorial transport. In most epithelia maintenance of vectorial function depends on the cytoskeleton. Capsule/epithelium preparations from human donor lenses have been used for immunohistochemical investigations of both normal epithelial cell cytoskeletal structure, and of structural changes induced by increasing cell calcium. A sustained increase in intracellular calcium, induced by incubation with A23187 and W7, led to a loss of cytoskeletal organisation. Changes induced depolymerisation of cytoplasmic actin filaments, disaggregation of microtubules and initial thickening, followed by breakdown, of vimentin intermediate filaments. In addition, spectrin staining, normally confined to the basal-lateral plasma membranes, became diffuse within the cytoplasm. Such disruptions of cytoskeletal structure would decrease ionic control, leading to increasing osmotic stress.