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EDWARD COTLIER, CLAUDIA BEATY; The Role of Na+ Ions in the Transport of α-Aminoisobutyric Acid and Other Amino Acids into the Lens. Invest. Ophthalmol. Vis. Sci. 1967;6(1):64-75.
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The transport systems for α-AIB and neutral, acid, and basic amino acids into lens were found to comprise a Na+-dependent and a Na+-independent component. Na+ ions, required for 60 to 70 per cent of 14C-α-AIB transported into rabbit lens, were combined with α-AIB molecules in a 1:1 ratio while transported by a common "carrier" system. However, Na+ ions did not affect the diffusion constant nor the 14C-α-AIB efflux rates from the lens. The in vitro lens incubations showed accumulation by the lens and against the concentration gradient of 14C-α-AIB and other 14C-amino acids. Throughout the incubation periods, Na+ ions transported with the amino acid continued to be actively extruded from the lens. The Na+ deprivation effects closely resembled ouabain inhibitory effects on α-AIB transport, and were both exerted in the lens epithelium. These restdts, and the independence of the lens α-AIB and K+ or Rb+ carriers, established the presence of a Na+ ions link between the Na+-dependent fraction of α-AIB and other amino acid transport systems and the ouabain-sensitive Na+-K+ "pump."
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