Steady state distribution of free amino acids in the aqueous humours, vitreous body and plasma of the rabbit

Abstract

The purpose of this investigation is to provide comparative quantitative data on the composition of amino acids in the intraocular fluids and plasma. The concentration of free amino acids in the aqueous humour of the posterior and anterior chambers, vitreous body and plasma of rabbits has been determined by ion exchange chromatography. Except for glycine, proline and threonine, the concentration of all the amino acids that could reliably be determined is greater in the aqueous humour of the posterior and anterior chambers than in plasma withdrawn at essentially the same time. The concentration of all the amino acids in the posterior and anterior chambers is approximately the same with the exception of glycine, which is present in appreciably higher concentration in the anterior than in the posterior chamber. The concentration of all amino acids, except glutamic acid, is significantly lower in the vitreous body than in the aqueous humour of both chambers and in plasma. The observation that the concentration of most of the free amino acids in the aqueous of the posterior chamber is higher than in plasma leads to the conclusion that at least some of these compounds are transported across the ciliary epithelium by an active process in addition to diffusion. Some evidence is adduced which suggests that there may also be active transport across the iris.