Protein synthesis in tissues and in the whole body of laying hens during egg formation

The present study was conducted to investigate whether or not protein synthesis in tissues and in the whole body of laying hens would be affected by the position of an ovum passing along the oviduct during egg formation. Protein synthesis in tissues was measured in vivo by a primed-continuous infusion of [15N]methionine for 3 h, finishing at the time when an ovum would have stayed at one of the segments within the oviduct, i.e., infundibulum, magnum, isthmus, uterus, or vagina. The dissection of the entire oviduct immediately after the isotope infusion confirmed whether or not the ovum was in the expected position. Whole-body protein synthesis, estimated from plateau enrichment of free [15N]methionine in plasma at the end of the infusion, was not significantly affected by the position of an ovum along the various segments of the oviduct. The highest values were observed in the entire oviduct when an ovum was in the magnum portion, both for protein synthesis and protein synthesis per unit of RNA. Protein synthesis per unit of RNA in the sum of tissues other than the liver and oviduct was highest when an ovum was in the isthmus. The synthesis of liver protein was relatively constant and was not significantly affected by the position of the ovum passing along the oviduct.