Abstract Aqueous humor was once thought to be a dialysate of plasma, or to be secreted as such by the ciliary body in a manner analogous to secretion of saliva by the salivary gland. Many observations on aqueous humor, both experimental and clinical, could not be accounted for on the basis of either of these suggested mechanisms of aqueous humor formation. Accordingly, a theory was evolved which envisaged these two processes, secretion and diffusion (dialysis), as taking place simultaneously.* Recent studies of the chemistry of the posterior chamber aqueous humor3 have provided additional evidence that aqueous humor is formed by at least two processes and, in addition, have shown that there are two kinds of aqueous humor in the eye: one in the posterior chamber, and another, having a different composition, in the anterior chamber. Much more experimentation is required, however, to elucidate fully the general nature of aqueous humor References 1. References 1 and 2. 2. References 4 through 11. 3. References 12 and 13. 4. References 14 and 15. 5. References 6 and 7. 6. No attempt will be made in this paper to distinguish between entrance into the anterior chamber from these sources and from the iris. 7. The experimental error involved was approximately 1%. 8. Davson.15 Friedenwald, J. S.: Personal Communication to the authors. 9. References 12 and 15. 10. References 1 and 5. 11. dC Aq.ant. =kdiff.ant. (Cpi.—C Aq.ant.)—kflow C Aq.ant. dt 12. dCAq.ant.=ksec.Cpi.—kflow C Aq.ant. 13. The processes responsible for such transport are called secretion. The term is being retained until such time as the nature of the processes is sufficiently understood to make appropriate introduction of a more specific word. It is used only in a broad general sense, however, and is analogous to that proposed by Kinsey and Báráy in 1949 in considering transport into the anterior chamber, where it was emphasized that the term implies only a net transport into the anterior chamber without any other physiological implications. 14. Kinsey and Grant,19 among others (Davson and Matchett14), have previously employed thiocyanate as a test substance in ocular experiments. To determine the amount of thiocyanate bound to plasma proteins, they added known amounts of this substance to plasma and then either ultrafiltered or dialyzed the plasma. The authors found that the concentration of thiocyanate in the ultrafiltrate or in the dialysate was less than in the mother liquid. Similar results were obtained by Davson and associates,20 who also dialyzed samples of plasma containing thiocyanate. Both groups concluded that approximately 20% of thiocyanate is bound to plasma protein, and therefore corrected all of the data to include only diffusible thiocyanate. In the present experiments the procedure of ultrafiltration was again performed and a similar result was obtained; however, the observation of an occasional steady-state ratio Aq.ant. (in nephrec-Cpi. tomized animals) in excess of 1 led us to search for the cause of the apparent discrepancy. Several fruitless leads were pursued. We then observed that the distribution of the color-producing material in the aqueous humor and the plasma of control animals, to which no thiocyanate had been given, was different from the apparent distribution under steady-state conditions after injection of thiocyanate. The value for the steady-state ratio Cpi.nt. before injection of thioCpi. cyanate was approximately 0.5, whereas after injection it was approximately 0.8. This suggested that at least some of the material normally present in rabbit plasma and aqueous humor which produces a color similar to that produced by thiocyanate in analysis was bound to the plasma protein. Thus, any procedure, such as ultrafiltration or dialysis, which concentrates the protein would be expected to raise still further the concentration of the color-producing blank. This was confirmed experimentally by ultrafiltration of normal plasma and plasma taken from nephrectomized animals, many of which showed still greater than normal concentrations of the color-producing material in their plasma. Further experimentation showed that when allowance was made for this color-producing substance, the concentrations of thiocyanate in the mother liquid and ultrafiltrate were so nearly alike that they lay within the experimental errors involved. As a consequence, we concluded that no appreciable amount of thiocyanate is bound to protein; hence no correction was made for nondiffusible thiocyanate in the experiments reported in this paper. The ultrafiltration procedure can be conveniently carried out by placing a sheet of Cellophane over the screen of an ordinary Seitz filter and applying pressure up to 100 lb. per square inch from a tank of compressed nitrogen. 15. The value for kdiff.post.En. will differ from that of k'diff.post.En. because, as with small kflow and large Kflow, the effect on the concentrations of the substance in any particular chamber will vary inversely with the volumes involved. The relationship in this instance is: V En.k' diff.post.En.= V post.kdiff.post.En. (5) 16. The concentration of test substances in the plasma at time intervals less than 20 minutes varies considerably from animal to animal, so that the relative aqueous concentrations at times less than 20 minutes are known with less certainty than those representing larger time intervals. 17. References 5 and 25. 18. Kinsey, V. E., and Grant, W. M.: Secretion-Diffusion Theory of Intra-Ocular Fluid Dynamics , Brit. J. Ophth. 28:355, 1944.Crossref 19. Kinsey, V. E.: A Unified Concept of Aqueous Humor Dynamics and the Maintenance of Intraocular Pressure: An Elaboration of the Secretion-Diffusion Theory , Arch. Ophth. 44:215, 1950.Crossref 20. Kinsey, V. E.: Comparative Chemistry of Aqueous Humor in Posterior and Anterior Chambers of Rabbit Eye: Its Physiologic Significance , A. M. A. Arch. Ophth. 50:401, 1953. 21. Friedenwald, J. S., and Pierce, H. F.: Circulation of Aqueous: I. Rate of Flow , Arch. Ophth. 7:538, 1932.Crossref 22. Kinsey, V. E., and Grant, W. M.: Mechanism of Aqueous Humor Formation Inferred from Chemical Studies on Blood-Aqueous Humor Dynamics , J. Gen. Physiol. 26:131, 1942.Crossref 23. Palm, E.: On the Passage of Ethyl Alcohol from the Blood into the Aqueous Humour , Acta ophth. 25:139, 1947.Crossref 24. Palm, E.: On the Phosphate Exchange Between the Blood and the Eye: Experiments on the Entrance of Radioactive Phosphate into the Aqueous Humour, and Anterior Uvea and the Lens , Acta ophth. , (Supp. 32) , 1948. 25. Bárány, E., and Kinsey, V. E.: Rate of Flow of Aqueous Humor: I. Rate of Disappearance of Para-Aminohippuric Acid, Radioactive Rayopake, and Radioactive Diodrast from the Aqueous Humor or Rabbits , Am. J. Ophth. 32:177 (June, (Pt. II) ) 1949. 26. Kinsey, V. E., and Bárány, E.: Rate of Flow of Aqueous Humor: II. Derivation of Rate of Flow and Its Physiologic Significance , Am. J. Ophth. 32:189 (June, (Pt. II) ) 1949. 27. Palm, E.: Passage of Radioactive Sodium from the Blood to the Ciliary Body and the Aqueous Humour: An Attempt to Locate the Barrier Between the Blood and the Aqueous Humour , Acta ophth. 29:269, 1951.Crossref 28. Ross, E. J.: Circulation of the Aqueous Humour and the Experimental Determination of Its Rate of Flow , Brit. J. Ophth. 36:41, 1952.Crossref 29. Goldmann, H.: Über Fluorescein in der menschlichen Vorderkammer: Das Kammerwasser Minutenvolumen des Menschen , Ophthalmologica 119:65, 1950.Crossref 30. Grant, W. M.: Tonographic Method for Measuring the Facility and Rate of Aqueous Flow in Human Eyes , Arch. Ophth. 44:204, 1950.Crossref 31. Davson, H., and Matchett, P. A.: Kinetics of Penetration of the Blood-Aqueous Barrier , J. Physiol. 122:11, 1953. 32. Davson, H.: Some Problems Concerning the Formation and Circulation of the Aqueous Humour , Brit. M. Bull. 9:5, 1953. 33. Friedenwald, J. S.: Dynamic Factors in the Formation and Re-Absorption of Aqueous Humour , Brit. J. Ophth. 28:503, 1944.Crossref 34. Trimmer, J. D.: Response of Physical Systems , New York, John Wiley & Sons, Inc., 1950, p. 268. 35. Kinsey, V. E.: Assembly for Positioning Cuvettes Used for Microanalysis with Beckman Spectrophotometer , Analyt. Chem. 22:362, 1950.Crossref 36. Kinsey, V. E., and Grant, W. M.: Further Chemical Studies on Blood-Aqueous Humor Dynamics , J. Gen. Physiol. 26:119, 1942.Crossref 37. Davson, H.; Duke-Elder, W. S.; Maurice, D. M.; Ross, E. J., and Woodin, A. M.: Penetration of Some Electrolytes and Non-Electrolytes into the Aqueous Humour and Vitreous Body of the Cat , J. Physiol. 108:203, 1949. 38. Rietz, H. L.: Handbook of Mathematical Statistics , New York, Houghton Mifflin Company, 1924, p. 54. 39. Copeland, R. L., and Kinsey, V. E.: Determination of Volume of the Posterior Chamber of the Rabbit's Eye , Arch. Ophth. 44:515, 1950.Crossref 40. Bárány, E., and Wirth, A.: An Improved Method for Estimating Rate of Flow of Aqueous Humour in Individual Animals , Acta ophth. 32:99, 1954.Crossref 41. Kinsey, V. E.: Chemical Composition and Osmotic Pressure of the Aqueous Humor and Plasma of the Rabbit , J. Gen. Physiol. 34:389, 1951.Crossref 42. Kinsey, V. E.; Grant, W. M.; Cogan, D. G.; Livingood, J. J., and Curtis, B. R.: Sodium, Chloride, and Phosphorus Movement and the Eye , Arch. Ophth. 27:1126, 1942.Crossref 43. Maurice, D. M.: Permeability to Sodium of the Living Rabbit's Cornea , J. Physiol. 112:367, 1951.
A.M.A. Archives of Ophthalmology – American Medical Association
Published: Mar 1, 1955
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