In ovo and in culture development of chick retinal angiotensin converting enzyme

The activity of angiotensin I-converting enzyme (ACE, EC 3.4.15.1), measured using Hip-His-Leu as substrate, was determined in the developing chick retina, and in monolayer and aggregate cultures of embryonic retinal cells. ACE specific activity in chick retinal homogenate increased 86-fold from embryonic day 13 until the 7th post-hatching day. The development of ACE activity occurred in parallel with that reported for synapse and photoreceptors. ACE activity expression in aggregates, but not in monolayer culture, was similar to that observed in the developing retina in ovo. At culture, day 13, ACE specific activity was 11.8-fold higher in the aggregate than in the dispersed cell culture, and was comparable to that in a 21-day-old embryonic intact retina. Our results suggest that histotypic association of retinal cells during development may be an important event controlling the expression of ACE activity in the CNS.