Partitioning of the aqueous outflow in rat eyes.

Purpose: To determine the effect of molecular size on the drainage route of dextrans injected into the rat anterior chamber (AC).

Methods: Anesthetized adult rats received monocular AC injections of a mixture of 3-kDa dextran-cascade blue, 40-kDa dextran-Texas red, and 500-kDa dextran-FITC. After exsanguination of the rats 2, 4, 6, 12, 24, or 72 hours later, the eyes, facial lymph nodes, and cervical lymph nodes were isolated, and the total content of each dextran type was determined by spectrofluorometry. Also, lymph nodes were evaluated histologically 4 and 24 hours after AC injection of 40-kDa dextran-FITC.

Results: The speed of tracer exit from the eye varied with 3-kDa dextran > 40-kDa dextran > 500-kDa dextran. No 3-kDa dextran was detected in either facial lymph nodes or cervical lymph nodes at any time point. The average recovery of 40-kDa dextran in the facial and cervical lymph nodes peaked at 52.6% of the amount injected. In contrast, average recovery of 500-kDa dextran in the facial and cervical lymph nodes peaked at 1.8% of amount the injected. Histology showed 40-kDa dextran was mostly contained within lymph node cells at both 4 and 24 hours after injection.

Conclusions: Transport of 40-kDa dextran from the AC to the facial lymph nodes and cervical lymph nodes is markedly more efficient than that of 500-kDa dextran. In contrast, there is negligible transport of 3-kDa dextran. These results demonstrate that different sized aqueous macromolecules can exit the eye by different routes.