ATPases and lens ion balance.

In the lens, different cells appear to be specialized such that some have a high capacity for energy-dependent ion transport while others do not. This short review describes the distribution of functional Na,K-ATPase activity and Ca-ATPase activity in the lens. Movement of ions in the extracellular space between lens fibers, a topic studied by David Maurice 25 years ago, is discussed together with cell-to-cell movement of ions which is facilitated by extensive coupling in the lens cell mass. The expression of different Na,K-ATPase and Ca-ATPase isoforms in lens epithelium and fiber cells is considered along with mechanisms that potentially regulate the activity of these transport proteins.