Protein turnover in tissues of the rat fetus following maternal starvation.

The effects of maternal starvation upon protein turnover in various tissues of the fetal rat were determined. Protein synthesis was determined in fetal tissues by the intravenous injection of "massive" amounts of 3H-phenylalanine into the maternal circulation, followed by measurements of tissue free and protein-bound phe specific radioactivity in fetal diaphragm, heart, liver, and brain. Rates of protein degradation in fetal tissues were assessed by subtracting protein accretion rates from protein synthesis. Fractional rates of protein synthesis were minimally affected by maternal starvation in diaphragm, heart, and brain. The major factor contributing to reduced fetal protein accretion in these fetal tissues during maternal starvation was enhanced protein breakdown. These findings differ from those previously reported in young adult rodents following fasting or malnutrition.