Protein Anabolism in the Organs and Tissues of Pregnant Rats at Different Levels of Protein Consumption

Abstract

The total quantity of protein formed during pregnancy is dependent on the protein intake. At low levels the quantity newly formed is even less than that of non-pregnant controls but with increasing protein intake it rises high above the control values and after attaining a maximum decreases as unusually large amounts of protein are consumed. The protein added to the mother's body (total protein less the protein of the uterus and its contents) is considerably less than that of non-pregnant rats when the protein intake is reduced to a gram per day, but when 2 or 3 gm. are eaten daily, the body of the pregnant rat gains more protein than the bodies of controls. In the organs the main effect of pregnancy is a pronounced increase in the protein of the liver at moderate and high levels of protein consumption. The concentration of protein in the organs and tissues of pregnant rats is lower than that in non-pregnant rats at all levels of protein consumption. An attempt to reproduce in non-pregnant rats part of the hormone conditions of the pregnant state by the injection of estradiol propionate failed to support the hypothesis that the lowered protein concentrations were due to an increase in estrogenic substances. At the end of pregnancy the gross distribution of protein in the body (organ or tissue protein per 100 gm. total protein) is not appreciably influenced by the amount of protein that has been taken as food. Roughly 8% of the total protein is assigned to the uterus and embryos, 80% to the carcass and blood and 12% to the internal organs. All of the protein of the uterus and its contents represents that deflected from the carcass and blood which, in controls, accounts for 88% of the total. The proportion allocated to the internal organs is no different from that found in non-pregnant rats. Although the proportion of the total protein assigned to the internal organs is about the same as the proportion found in non-pregnant animals the distribution among the various organs is different. In pregnant rats the liver obtains more protein and the other organs less. The preponderance of liver protein increases with increase in protein consumption.