Sodium and Chloride of the Aqueous Humour of Normal and Scorbutic Guinea-Pigs

Abstract

THE study made by Scholz (1950Scholz ( , 1953 of the distribution of sodium between the aqueous humour and the plasma of the guinea-pig brought to light two interesting results. First, it showed that the aqueous-plasma distribution of sodium in the guinea-pig was markedly different from that found in other species which had been investigated. The value of the steady-state ratio of sodium in the guinea-pig aqueous to that in the plasma was found to be 1 024±0 0055 (23) (Scholz, 1950), compared with 0-936 in the horse; 0-945 in the steer; 0 943 sheep; 0 935 pig; 0 940 goat; 0 943 rabbit; 0 965 dog; and 0 960 cat (Davson, 1953). Secondly, Scholz (1953) showed that in the scorbutic guinea-pig the steady-state ratio fell to 0-948±0-01 (21), a value very close to that for plasma and its dialysate; this suggested to Scholz " that ascorbic acid is essential for the secretion of sodium into the aqueous from the plasma". This result was therefore considered to lend support to the hypothesis of Friedenwald and others (1943) regarding the part played by ascorbic acid in the formation of the aqueous humour. Since this finding has such a direct bearing on one of the central problems of aqueous humour dynamics, namely the factors responsible for the formation of the aqueous, it was decided to submit it to further test.Let us assume that scurvy is without effect on the plasma sodium concentration (an assumption which is justified below), and that throughout Scholz's experiments it remained constant at about 140 mEq./kg. H20, then the ratio of 1 024 for the normal animal indicates that the aqueous sodium concentration was 143 36 mEq./kg. H20. In the scorbutic animal, with a ratio of 0-948, the aqueous sodium concentration must have been about 132-72 mEq./kg. H2O. These figures show that scurvy is accompanied by a decrease in the aqueous sodium concentration of about 10-64 mEq./kg. H2O, and further that to maintain electrical neutrality there must have been either an entrance of an equivalent amount of other cations, or an equivalent decrease of anion, or compensatory changes in both.It is extremely unlikely on a priori grounds that such a large loss of sodium could be made good by other cations without profound alterations in the character of the blood-aqueous barrier and there are no indications at the moment that such alterations have occurred. It seems much more reasonable to suppose that any necessary adjustment would manifest itself in the

Changes in the Vitreous Body in Scurvy

“…T h e water content of plasma was estimated to be 92 @lo, that of aqueous humour and vitreous Only a few experiments were made and the results must be treated with reservation. T h e ratio of aqueous humour sodium to plasma sodium a t equilibrium in normal animals saturated with ascorbic acid is 1.02, a value similar to those reported by Scholz (1953) and Ridge (1955). I n advanced scurvy, there appears to be a slight increase in this value, a finding quite a t variance with that of Scholz and due mainly to a rise in the sodium content of the aqueous humour.…”

“…He took this as confirmation of the part of ascorbic acid in the secretion. Ridge (1955) repeated these experiments with moderately scorbutic animals (10-12 days), in whose aqueous humours no ascorbic acid was found. He also determined the chloride ratio for aqueous humour and plasma in order to find whether alterations also occurred with respect to anions.…”