Plasma Proteins And Protein Synthesis In Rat Uterus During Decidual Development

An in vivo isotope dilution experiment was designed to test the idea that the mechanism of tissue growth in the development of deciduomata, following uterine trauma in pseudopregnant rats, might involve utilization of plasma proteins by growing decidual cells. Uterine growth was induced in pseudopregnant rats 2 days after the injection of plasma protein-S35 and plasma protein- I131. The rats were autopsied after 3 and 5 days of uterine growth, when the total protein of the uterus had increased 2-fold and 5-fold, respectively. The specific activity (cpm/mg) of methionine-S35 isolated from endometrial and myometrial protein was far less than that isolated from plasma protein. Measurement of I131 in the tissue protein samples (before hydrolysis) provided corrections for contaminating plasma protein. The I131 data also indicated that extensive infiltration of plasma protein into interstitial spaces of the growing decidual uterus occurred. Nevertheless, these extravascular plasma proteins apparently remained stable during the uterine growth period, as indicated by the relatively low specific activity of methionine-S36 in the uterine tissue proteins.