Nucleic acid metabolism of placenta and fetus.

The preceding résumé of placental nucleic acid metabolism indicates considerable changes in RNA and DNA during the course of pregnancy in both human and animal experiments. The presence of an active protein-synthesizing apparatus closely allied with DNA and RNA metabolism has been observed in placental preparations; future studies should reveal even more direct relationships. The specific regulatory role of nucleic acids in normal and abnormal placental function is still unknown. In truth, such specific regulatory or control mechanisms are generally unproved among the entire mammalian (eukaryotype) system. Progress in learning about placental function and control may require more detailed information regarding RNA metabolism from molecular biology. The regulatory control of fetal or intrauterine growth as it relates to nucleic acids remains even more obscure. One of the major drawbacks in this study has been our inability to label fetal tissues adequately during the major portion of the pregnancy. The problem is made even more complex by the many factors involved in intrauterine growth, such as blood volume, uterine blood supply, oxygen flow and transfer, hormonal effects, and nutritional status, in addition to nucleic acids.