Elaboration of Bicarbonate Ion in Intraocular Fluids : VI. Rabbit Aqueous Humor Studies with NaHC14O3

Abstract

Christiansson and Palm1 and Kinsey and Palm,2 as well as Friedenwald and Becker,3 have shown that failure to take into account the dynamic properties of the chemical components of the vitreous humor in diffusional exchange with those in the aqueous humor leads to inaccurate estimates of the rate of flow of aqueous humor. Furthermore, determination of the distribution of substances in the different sections of the vitreous humor gives some idea as to the routes by which they enter. Thus, Duke-Elder and Davson,4 by a modification of the technique employed by Adler,5 concluded from the uniform distribution of glucose in the vitreous humor under normal conditions and when the blood sugar level was high that glucose diffuses into the vitreous humor of a cat throughout the entire posterior segment of the eye from the uveal, choroidal, and retinal vessels, rather than from the posterior chamber aqueous humor alone. A similar route of entry was shown by Davson and co-workers 6 to exist for urea and thiocyanate. From the results of experiments with radioactive sodium and potassium ions they also suggested that, since there was a gradation in concentration from the anterior to the posterior section of the vitreous humor, these ions penetrate predominantly from the ciliary body and iris areas and that penetration from the choroid and retinal circulation was comparatively small. Because of the important role that the bicarbonate ion is believed to play in the formation of aqueous humor and in the maintenance of intraocular pressure, it was considered desirable to determine the distribution of the ion in the vitreous humor and to correlate this with the concentration in the blood plasma and aqueous humors of the anterior and posterior chambers. This paper represents a determi¬ nation of the normal distribution of bicarbonate ion in the vitreous humor of the rabbit eye. In another paper7 the effect of raising the bicarbonate ion con¬ centration in the blood upon that in the vitreous humor will be reported. Procedure Pigmented rabbits weighing between 4 and 6 lb. were used in all experi¬ ments. The animals were killed by air embolism and placed in an upright position for one to one and one-half minutes to allow drainage of blood from the ocular vessels. The eyes were immediately enucleated and placed in a tube surrounded