INSULIN SYNTHESIS IN CHICK-EMBRYO RETINAS DURING DEVELOPMENT

Retinas of chick embryos contain insulin (1) and further, are capable of synthesizing it, as demonstrated by incubating retinas at different ages (7th - 18th day) with [H-3]leucine. The synthesized radioactive insulin was isolated and assayed by means of a HPLC procedure. The syn thesis of insulin was found to be highest in the youngest retinas stud ied (day 7), afterwards it declined with age except for an increment f ound at 14 - 15 day. Explants of chick embryo retinas, cultured in vit ro, rapidly degraded insulin. Nevertheless, the content of immunoreact ive insulin in retinal explants diminished slowly with the age of cult ure, so that, after 8 days of incubation, it was about 60% of the cont ent found in the retinas at the beginning of incubation. This was proo f that cultured explants ale capable of efficiently synthesizing insul in. The synthesized [H-3]insulin was released from explants into the m edium. This was evident also after 6-8 days in culture.