Na,K-ATPase activity in the lens is high only in the equatorial region of the epithelium monolayer even though central epithelial and many fiber cells possess Na,K-ATPase protein. Using intact porcine lenses we are studying how Na,K-ATPase activity is regulated through the action of Src family tyrosine kinases. G protein-coupled receptors are able to selectively activate Src kinases. We think different kinases may be responsible for Na,K-ATPase activation vs inhibition.