Myoglobin Synthesis Studied In-Vitro In Chick Embryo

Chick embryos (as young as Hamburger-Hamilton stages 4–6) and their isolated body parts were capable of myoglobin synthesis, when measured with an in vitro system using incorporation of lysine-U- 14 C into precipitates formed with specific antimyoglobin serum. Crude minces and homogenates were capable of continuing this incorporation for 5–7 hours. Myoglobin, as well as total soluble protein, synthetic ability increased with advancing age, most strikingly between age 2 and 4 days in ovo . Older embryos failed to demonstrate continuing increases in myoglobin synthetic ability, while they did increase their capacity for production of total soluble proteins. Approximately 7–8% of total soluble protein synthesis of 1-day-old embryos was detectable as incorporation into myoglobin, while only about 1% of total soluble protein synthesis of 7-day-old embryos could be accounted for as myoglobin production. Most myoglobin synthesis in the 1-day-old embryo (60%) occurred in the head region. With age, the head became relatively less important as a site of myoglobin synthesis. The cardiac area maintained a relatively constant portion of the total body myoglobin synthesis, approximately 25%, while the proportion which occurred in the hind-body region rose with increasing age. There was a reduction in the ratio of myoglobin to protein synthesis in each of the chick body parts with age. This was most prominent, however, in the head and midbody regions and was due to a greater relative synthesis of proteins other than myoglobin by these embryo parts.