Myo-inositol: active transport by the crystalline lens.

>C myo-inositol was actively transported into rabbit crystalline lenses incubated in Tijrode's medium. The lens/media accumulation ratios of C myo-inositol reached values of 10 to 12 after 24 hr., in vitro incubations. The active transport of ^C myo-inositol into the lens was markedly decreased by metabolic inhibitors of glycolysis and oxidative phosphorylation, and by ouabain, or by an absence of Na ions in the incubation media. Kinetic studies revealed a Km of 0.07 mM. per liter for myo-inositol transport into lens. The efflux of C myo-inositol from preloaded lenses was slow, but it increased by iodoacetate. Gas chromatography determinations of myo-inositol in the lens and intraocular fluids were as follows (averages in ynM. per kilogram of water): lens, 8835; anterior chamber aqueous humor, 135.1; posterior chamber aqueous humor, 93.2; vitreous humor, 235.5; and serum, 40.9. The studies support the concept of active transport and slow efflux of myo-inositol into the lens, as well as the presence of transport mechanisms specific for cyclic alcohols in tissues.