Ontogenesis of prolyl endopeptidase in the chick retina

The time course of prolyl endopeptidase (PE) activity, measured using 7-(N-succinyl-Gly-Pro)-4-methyl-coumarinamide as substrate, was determined in the developing chick retina, and in monolayer and aggregate culture of embryonic retinal cells. PE activity/retina increased 12.5-fold between embryonic days 7 and 12 and remained constant from the 12th embryonic day until the 3rd post-hatched day. PE activity/retina decreased 2.3-fold from the 3rd to the 9th post-hatched day. The levels of PE specific activity in aggregates and in retina were similar, whereas they were 44-81% higher in monolayer than in aggregate cultures between 3 and 13 days in culture. The data suggest that the development of PE activity and of plexiform layers occurs in parallel during chick retina ontogenesis, and that the chick retina can be an adequate in vivo and in vitro model to study PE development.