Unidirectional transport mechanism of horseradish peroxidase in the vessels of the iris.

When horseradish peroxidase (HRP) is introduced into the blood stream it is retained in the lumen of the iridial vessels. In this paper, we report that when the same tracer is perfused into the anterior chamber of macaque monkeys, it permeates the stroma of the iris and penetrates the lumen of iridial vessels by transcellular vesicular transport. This unidirectional movement of HRP out of the eye is not inhibited by ouabain or fluoroacetate.