Summary
A study has been made of the rate of accumulation of Na24, Cl36 and HC14O3 in the posterior and anterior chambers of the rabbit eye. From the data obtained, the diffusion constant between plasma and posterior chamber and the concentration of these ions in the fluid secreted by the ciliary process has been calculated. The mathematical method employed is believed to give rise to more realistic values for the loss of the test substances to the lens and vitreous than used heretofore since it obviates the necessity for assuming that the fluids in these structures are well stirred. An analog computer was used to facilitate the computations.
The ionic composition of the secreted fluid was estimated from the computed concentrations for Na24 and Cl36 on the basis of a number of assumptions concerning the total concentration of anions required to maintain electrical neutrality.
The secreted fluid differs most strikingly from the plasma, and to a lesser extent from the aqueous of the posterior chamber, in the relatively high concentration of bicarbonate and low concentration of chloride. Because of uncertainties in knowledge of the proportion of fluid entering the posterior chamber by diffusion and bulk flow, the concentrations of all the substances in the secreted fluid must be considered minimal, although, percentagewise, they are correct within the accuracy of the methods employed.
An electrical analog computer was employed to determine the proportion of the total amount of sodium and chloride which enters the posterior chamber by secretion. The calculations were based on a new formulation of aqueous humor dynamics which takes into account more realistically the role played by the vitreous humor. From the data obtained, the fluid secreted by the ciliary processes was estimated to consist chiefly of about equal parts sodium chloride and sodium bicarbonate, thus differing still more widely in composition from the plasma than the aqueous humor of either the posterior or anterior chamber.
Résumé
A l'aide d'une machine à calculer électronique la quantité de sodium et de chlore qui entre par sécrétion dans la chambre postérieure a été déterminée. Les calculs ont été basés sur une nouvelle formule qui se rapproche plus de réalité que celles utilisées jusqu'ici et prend en considération le rôle joué par le corps vitré. D'après les résultats ainsi obtenus, on peut conclure que le liquide sécrété par les procès ciliaires contient essentiellement du chlorure de sodium et du bicarbonate de soude à parties égales. Il est donc, du fait de sa composition, encore plus éloigné du plasma que l'humeur aqueuse de la chambre postérieure et de la chambre antérieure.
Zusammenfassung
Mit Hilfe einer Elektronenrechenmaschine wurde der Gehalt an Chlor und an Natrium in der Flüssigkeit bestimmt, die durch Sekretion in die Hinterkammer gelangt. Hierbei bediente man sich einer neuen Formel, die realistischer ist als die älteren und die Rolle des Glaskörpers mit in Betracht zieht. Es ergab sich, dass die von den Ziliarprozessen sezernierte Flüssigkeit in der Hauptsache gleiche Teile von Kochsalz und Natriumbikarbonat enthält. Ihre Zusammensetzung ist also sehr entfernt von der des Plasmas, jedenfalls entfernter als es die des Kammerwassers in der hinteren oder in der vorderen Kammer ist.
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Abbreviations
- Ahv :
-
Area posterior chamber - vitreous interface cm2
- α:
-
Donnan factor
- Ca :
-
Concentration aqueous humor anterior chamber
- Ch :
-
Concentration aqueous humor posterior chamber
- Cp :
-
Concentration plasma
- Cs :
-
Concentration of secreted fluid
- Cv :
-
Concentration vitreous humor
- D:
-
Diffusion constant
- kd.hv :
-
Transfer coefficient by diffusion posterior chamber to vitreous
- kd.ph :
-
Transfer coefficient by diffusion plasma to posterior chamber
- kfa :
-
Transfer coefficient by flow into and out of anterior chamber
- kfh :
-
Transfer coefficient by flow into and out of posterior chamber
- M:
-
Mass
- Va :
-
Volume of anterior chamber
- Vh :
-
Volume of posterior chamber
- Vv :
-
Volume of vitreous
- x:
-
Space variable
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The study was supported in part by research grant B-1100 from the National Institute of Neurological Diseases and Blindness of the National Institutes of Health, U.S. Public Health Service.
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Everett Kinsey, V., Reddy, D.V.N., Aitken, I. et al. An estimate of the ionic composition of the fluid secreted into the posterior chamber, inferred from a study of aqueous humor dynamics. Doc Ophthalmol 13, 7–32 (1959). https://doi.org/10.1007/BF00157905
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DOI: https://doi.org/10.1007/BF00157905