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. 1981 Jun;315:253–266. doi: 10.1113/jphysiol.1981.sp013746

Alpha-aminoisobutyric acid efflux from the cornea of the toad, Bufo marinus.

M C McGahan
PMCID: PMC1249381  PMID: 6796676

Abstract

1. Amino acids move into and out of the amphibian cornea across its inner aqueous, side only. Most alpha-aminoisobutyric acid (AIB) accumulation takes place in the corneal epithelium; the endothelium and stroma do not limit exchanges with these cells. The apical, or tear, surface of the epithelium is an impermeable barrier to the transport of amino acids. There are several sites or mechanisms by which AIB enters and leaves the cornea. 2. The entry of AIB is not Na-dependent; however, the exit site is very sensitive to changes in internal Na concentration. Any factor, such as ouabain or metabolic inhibitors, that increases internal Na, markedly stimulates AIB efflux. 3. Site are also present for the exchange of internal for external amino acids, and this process is Na-dependent. There was no measurable movement of Na into or out of the cells with these amino acids. Exchange efflux was more specific than uptake, since both alanine and leucine inhibit AIB uptake, but only alanine stimulates AIB efflux. 4. Although the largest amount of AIB accumulated by the cornea was present in the epithelium, evidence is presented that the endothelium and stromal keratocytes may also concentrate and retain amino acids.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Bentley P. J., McGahan M. C. Inhibitory action of DIDS on chloride transport across the amphibian cornea. J Physiol. 1980 Jul;304:519–527. doi: 10.1113/jphysiol.1980.sp013340. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Candia O. A., Bentley P. J., Cook P. I. Stimulation by amphotericin B of active Na transport across amphibian cornea. Am J Physiol. 1974 Jun;226(6):1438–1444. doi: 10.1152/ajplegacy.1974.226.6.1438. [DOI] [PubMed] [Google Scholar]
  3. Danisi G., Tai Y. H., Curran P. F. Mucosal and serosal fluxes of alanine in rabbit ileum. Biochim Biophys Acta. 1976 Nov 11;455(1):200–213. doi: 10.1016/0005-2736(76)90164-4. [DOI] [PubMed] [Google Scholar]
  4. Eddy A. A., Mulcahy M. F., Thomson P. J. The effects of sodium ions and potassium ions on glycine uptake by mouse ascites-tumour cells in the presence and absence of selected metabolic inhibitors. Biochem J. 1967 Jun;103(3):863–876. doi: 10.1042/bj1030863. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Friedenthal D. F., Scott W. N. Amino acid transport in the cornea. I. 3-Aminoisobutyric acid uptake in the toad. Biochim Biophys Acta. 1973 Oct 25;323(3):456–465. doi: 10.1016/0005-2736(73)90190-9. [DOI] [PubMed] [Google Scholar]
  6. HEINZ E., WALSH P. M. Exchange diffusion, transport, and intracellular level of amino acids in Ehrlich carcinoma cells. J Biol Chem. 1958 Dec;233(6):1488–1493. [PubMed] [Google Scholar]
  7. Jardetzky O. Simple allosteric model for membrane pumps. Nature. 1966 Aug 27;211(5052):969–970. doi: 10.1038/211969a0. [DOI] [PubMed] [Google Scholar]
  8. Johnstone R. M. Is Na+-dependent exchange diffusion a true exchange? J Biol Chem. 1979 Dec 25;254(24):12479–12483. [PubMed] [Google Scholar]
  9. Laris P. C., Bootman M., Pershadsingh H. A., Johnstone R. M. The influence of cellular amino acids and the Na+ : K+ pump on the membrane potential of the Ehrlich ascites tumor cell. Biochim Biophys Acta. 1978 Sep 22;512(2):397–414. doi: 10.1016/0005-2736(78)90263-8. [DOI] [PubMed] [Google Scholar]
  10. OXENDER D. L., CHRISTENSEN H. N. DISTINCT MEDIATING SYSTEMS FOR THE TRANSPORT OF NEUTRAL AMINO ACIDS BY THE EHRLICH CELL. J Biol Chem. 1963 Nov;238:3686–3699. [PubMed] [Google Scholar]
  11. Reddy D. V. Distribution of free amino acids and related compounds in ocular fluids, lens, and plasma of various mammalian species. Invest Ophthalmol. 1967 Oct;6(5):478–483. [PubMed] [Google Scholar]
  12. Riley M. V. A study of the transfer of amino acids across the endothelium of the rabbit cornea. Exp Eye Res. 1977 Jan;24(1):35–44. doi: 10.1016/0014-4835(77)90282-2. [DOI] [PubMed] [Google Scholar]
  13. SCHULTZ S. G., ZALUSKY R. INTERACTIONS BETWEEN ACTIVE SODIUM TRANSPORT AND ACTIVE AMINO-ACID TRANSPORT IN ISOLATED RABBIT ILEUM. Nature. 1965 Jan 16;205:292–294. doi: 10.1038/205292a0. [DOI] [PubMed] [Google Scholar]
  14. Scott W. N., Friedenthal D. F. A proposed role for ascorbate in the transport of amino acids and ions in the cornea. Exp Eye Res. 1973 May 24;15(6):683–692. doi: 10.1016/0014-4835(73)90002-x. [DOI] [PubMed] [Google Scholar]
  15. Thoft R. A., Friend J. Corneal amino acid supply and distribution. Invest Ophthalmol. 1972 Sep;11(9):723–727. [PubMed] [Google Scholar]
  16. Young J. D., Wolowyk M. W., Jones S. E., Ellory J. C. Sodium-dependent cysteine transport in human red blood cells. Nature. 1979 Jun 28;279(5716):800–802. doi: 10.1038/279800a0. [DOI] [PubMed] [Google Scholar]
  17. Zadunaisky J. A. Active transport of chloride in frog cornea. Am J Physiol. 1966 Aug;211(2):506–512. doi: 10.1152/ajplegacy.1966.211.2.506. [DOI] [PubMed] [Google Scholar]

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