Metabolic studies on calcium transport in mammalian lens

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Abstract
Three important findings concerning the Ca pump in a mammalian lens are reported. Glycolysis is sufficient to support active transport of Ca in the young rabbit lens. Epithelium posterior and anterior fibers are involved in Ca transport. Inhibition of glycolysis and the Ca pump result in Ca accumulation and subsequent opacification. That respiration does not contribute to the energy needs of the Ca2+ pump is based on results which demonstrate that cyanide, dinitrophenol and azide do not affect 45Ca efflux when glucose is present. Incubation of lenses for 20 h in the presence of cyanide fails to alter the internal concentration of Ca. The inhibition of glucose metabolism with iodoacetate (IAA) results in the accumulation of Ca to a level of 0.71 mM and the formation of superficial subcapsular opacities. Evidence that fibers are also responsible for Ca extrusion consists of 2 findings: removal of the epithelium from a lens results in Ca accumulation, but the addition of IAA to such a lens results in a further gain in Ca; and the accumulation of 45Ca across the posterior surface of a lens partially immersed in medium is accelerated following inhibition of glycolysis.