Aqueous Humor/plasma Chloride Ratios in Rabbits, Dogs, and Human Beings

The ratio of concentration of chloride in the aqueous humor compared with that in the plasma of rabbits, dogs, and human beings, was determined by the Schales and Sendroy methods. Consistent results were obtained in all the experiments by the Schales method with or without protein, and by the Sendroy method without protein. In the presence of protein, however, lower chloride concentrations were found in the plasma of dogs and human beings by the Sendroy method. The ratios in this instance were higher than values predicted on the basis of Gibbs-Donnan equilibrium and similar to those obtained by several previous investigators using the same method. With rabbits both methods gave essentially the same results under all conditions. The ratios (Schales and Sendroy) for the rabbits based on arterial plasma averaged 0.98, on venous plasma 1.00; the ratio (Schales) for the dog for venous plasma was 1.00; the ratio (Schales, protein present or removed; Sendroy, protein removed) for human beings, based on venous plasma, was approximately 1.03. Ratios of 1.08 for the dog and 1.07 for human beings were obtained by the Sendroy method in the presence of protein. Possible explanations for these apparent discrepancies are discussed. In dogs and in human beings, the major evidence supports the contention that the aqueous humor/plasma chloride ratio is not in excess of that predicted by the Gibbs-Donnan equilibrium and therefore requires no special explanation. In the rabbit all the evidence indicates that the chloride ratios are actually less than the value predicted by the Gibbs-Donnan equilibrium.