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. 1987 Apr;385:97–106. doi: 10.1113/jphysiol.1987.sp016486

The apparent reflexion coefficient of the leaky corneal endothelium to sodium chloride is about one in the rabbit.

S A Hodson 1, D M Lawton 1
PMCID: PMC1192339  PMID: 3656171

Abstract

1. Rabbit corneal thickness changes were measured after some of the NaCl in the bathing Ringer solution was substituted by a neutral sugar. 2. The response had three phases which could be closely modelled by three exponentials of different amplitudes and rate constants, originating from the time of the substitution. 3. The first, fastest, phase was interpreted as being driven by the pure osmotic pressure difference developed across the corneal endothelium by the difference between the removed NaCl and the added sugar in the bathing Ringer solution; the second was driven by the diffusion of NaCl out of the stroma; and the third, slowest, phase was driven by the diffusion of the added sugar into the stroma. 4. Consistent with the interpretation, only the third, slowest, phase had its rate constant dependent upon the nature of the substituting neutral sugar. 5. The amplitude of the pure osmotic phase was a linear function of the added sugar. Its amplitude was zero when an equal osmolarity of sugar was substituted for NaCl. 6. It was concluded that the reflexion coefficient of rabbit corneal endothelium to NaCl is the same as that to sucrose, raffinose and stachyose, i.e. about 1. 7. The calculated hydraulic conductivity of the endothelium plus stroma was about the same as that of stroma alone, and it was concluded that the hydraulic conductivity of corneal endothelium is large compared to corneal stroma. 8. It is proposed that most of the hydraulic flow in response to osmotic gradients passes through the cells, whereas salt diffuses through the paracellular route, resulting in an apparent reflexion coefficient of 1. 9. Thus, corneal endothelium is a 'leaky' (12 omega cm2) salt-permeable epithelium and, according to the present study, simultaneously a semi-permeable membrane. To resolve the terminology, we suggest the term 'bi-permeable' for such epithelia which have a high salt permeability but such a very high water permeability as to give apparent reflexion coefficients of 1.

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Selected References

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  1. Dikstein S., Maurice D. M. The metabolic basis to the fluid pump in the cornea. J Physiol. 1972 Feb;221(1):29–41. doi: 10.1113/jphysiol.1972.sp009736. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Ersser R. S., Andrew B. C. Rapid thin layer chromatography of clinically important sugars. Med Lab Technol. 1971 Oct;28(4):355–359. [PubMed] [Google Scholar]
  3. Fischbarg J., Lim J. J. Role of cations, anions and carbonic anhydrase in fluid transport across rabbit corneal endothelium. J Physiol. 1974 Sep;241(3):647–675. doi: 10.1113/jphysiol.1974.sp010676. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Fischbarg J., Warshavsky C. R., Lim J. J. Pathways for hydraulically and osmotically-induced water flows across epithelia. Nature. 1977 Mar 3;266(5597):71–74. doi: 10.1038/266071a0. [DOI] [PubMed] [Google Scholar]
  5. Green K., Green M. A. Permeability to water of rabbit corneal membranes. Am J Physiol. 1969 Sep;217(3):635–641. doi: 10.1152/ajplegacy.1969.217.3.635. [DOI] [PubMed] [Google Scholar]
  6. Green K., Otori T. Direct measurements of membrane unstirred layers. J Physiol. 1970 Mar;207(1):93–102. doi: 10.1113/jphysiol.1970.sp009050. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. HEDBYS B. O., MISHIMA S. Flow of water in the corneal stroma. Exp Eye Res. 1962 Mar;1:262–275. doi: 10.1016/s0014-4835(62)80010-4. [DOI] [PubMed] [Google Scholar]
  8. Hedbys B. O., Mishima S. The thickness-hydration relationship of the cornea. Exp Eye Res. 1966 Jul;5(3):221–228. doi: 10.1016/s0014-4835(66)80010-6. [DOI] [PubMed] [Google Scholar]
  9. Hodson S. A., Wigham C. G. Paracellular ionic and transcellular water diffusions across rabbit corneal endothelium. J Physiol. 1987 Apr;385:89–96. doi: 10.1113/jphysiol.1987.sp016485. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Hodson S., Miller F., Riley M. The electrogenic pump of rabbit corneal endothelium. Exp Eye Res. 1977 Mar;24(3):249–253. doi: 10.1016/0014-4835(77)90162-2. [DOI] [PubMed] [Google Scholar]
  11. Hodson S. The regulation of corneal hydration by a salt pump requiring the presence of sodium and bicarbonate ions. J Physiol. 1974 Jan;236(2):271–302. doi: 10.1113/jphysiol.1974.sp010435. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Hodson S., Wigham C. The permeability of rabbit and human corneal endothelium. J Physiol. 1983 Sep;342:409–419. doi: 10.1113/jphysiol.1983.sp014859. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Klyce S. D., Russell S. R. Numerical solution of coupled transport equations applied to corneal hydration dynamics. J Physiol. 1979 Jul;292:107–134. doi: 10.1113/jphysiol.1979.sp012841. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. MAURICE D. M. The permeability to sodium ions of the living rabbit's cornea. J Physiol. 1951 Feb;112(3-4):367–391. doi: 10.1113/jphysiol.1951.sp004535. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Maurice D. M. Cellular membrane activity in the corneal endothelium of the intact eye. Experientia. 1968 Nov 15;24(11):1094–1095. doi: 10.1007/BF02147776. [DOI] [PubMed] [Google Scholar]
  16. Mishima S., Hedbys B. O. The permeability of the corneal epithelium and endothelium to water. Exp Eye Res. 1967 Jan;6(1):10–32. doi: 10.1016/s0014-4835(67)80049-6. [DOI] [PubMed] [Google Scholar]

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