Steroid Maintenance of Pregnancy in Rats in the Absence of Dietary Protein1

Abstract

Investigation was made into the alterations of blood, liver, skeletal muscle, uterus, placenta and fetuses of mother rats fed a 0% casein diet and injected with estrone and progesterone from days 3-20 gestation. Successful maintenance of pregnancy by steroid injections into protein-depleted rats was not associated with increased food intake, decreased nitrogen excretion, excessive enlargement or mobilization of hepatic or uterine protein sources when compared with appropriate control animals. It is suggested that the transfer of maternal protein to developing fetuses in the absence of dietary protein emanates to a large extent from skeletal muscles where both total size and protein concentration were decreased in response to the steroid regimen. Muscle glycogen levels of the steroid-injected protein-depleted pregnant rats were markedly reduced as compared with complete diet-fed pregnant controls. Though smaller in size and fewer in number, the placentae of the experimental rats did not differ significantly from control placentae histologically or with respect to nucleic acid and protein concentrations.