A SIMPLIFIED 2-TIME-POINT METHOD FOR MEASURING WHOLE-BODY PROTEIN-SYNTHESIS IN CHICKEN EMBRYOS CULTURED IN-VITRO - RESPONSE TO FRAGMENTED BOVINE GROWTH-HORMONE

1. A simplified two-time-point method for measuring whole-body protein synthesis of chicken embryos cultured in vitro was developed. 2. The chicken embryos at 7 days of egg incubation age were cultured with a synthetic medium containing L-[4-H-3]phenylalanine in a rotatory whole-embryo culture apparatus for a period of up to 60 min. 3. An adequate combination of measurement time points was examined by comparing fractional synthesis rates calculated by the simplified two-time-point method with those estimated by a full curve-fitting method which would give best estimates. The effect of fragmented bovine growth hormone added to the culture medium on fractional synthesis rates was also tested. 4. The results indicated that the closest fractional synthesis rates by the simplified two-time-point method to the one by the full curve-fitting method were obtained by taking the time points of t(1) at 10 min and t(2) at 30 or 60 min with intraperitoneal injection of the tracer prior to the culture period. 5. With the simplified two-time-point method, the fragmentation of bovine growth hormone was shown to increase the biopotency in inducing fractional synthesis rates approximately 100 times as high as that of the intact growth hormone. 6. It was concluded, therefore, that the present assay method would be convenient and sensitive for searching physiologically active compounds in promoting growth and protein synthesis in the chicken.