THE ROLE OF SOLUBLE-PROTEINS IN GENERATING AQUEOUS OUTFLOW RESISTANCEIN THE BOVINE AND HUMAN EYE

Previous research has shown that wash-out in bovine and primate eyes c an be greatly reduced by perfusing with buffer containing 5-15% serum. It was suggested that protein diffusion from the iris root might rais e the in vivo protein concentration in the trabecular meshwork to a le vel much higher than in the anterior chamber. In this study, we invest igated the protein concentration in effluent from the outflow pathways in bovine and human eyes, its possible relationship to wash-out, and whether the reduction of wash-out was caused by a bulk protein effect. Bovine and human eyes were placed under silicone oil and perfused wit h buffer. Outflow facility was continuously determined while effluent was periodically collected from the surface of the eye, and the solubl e protein concentration in the effluent was determined. Separate studi es were conducted perfusing either albumin or gamma-globulin through b ovine eyes. Theoretical models were developed to study the transport o f protein into the perfusion fluid. In the bovine eyes, the initial pr otein concentration in the collected effluent was approximately 1% tha t of serum, much lower than the 10-15% buffer in serum required to pre vent wash-out. Furthermore, the rate of change of outflow facility sho wed a different dependence on perfused volume than did the protein con centration. Human eyes showed a much higher level of protein in the pe rfusate, that decayed over a much longer time period. A statistically significant correlation existed between outflow resistance and soluble protein concentration in both bovine and human eyes, However, modelli ng studies suggested that this correlation might be due to flow resist ance setting the flowrate which then determines the protein concentrat ion of the effluent. Separate experiments indicated that the decreased rate of wash-out caused by perfusion of 10-15% serum in buffer was no t due to either albumin or gamma-globulin alone. These results suggest that the reduction of wash-out observed in previous studies when seru m proteins were perfused through bovine and monkey eyes was not due to the general level of serum proteins but may instead be due to interac tions of a particular protein(s). (C) 1997 Academic Press Limited.