Phosphoribosyltransferase Activity during Early Mammalian Development

Abstract

The activities of hypoxanthine-guanine phosphoribosyltransferase and adenine phosphoribosyltransferase were determined in pre- and postimplantation mouse embryos and in preimplantation rabbit embryos. Both enzymes increase in activity during the preimplantation period, with hypoxanthine-guanine phosphoribosyltransferase having a sharp increase during the 3rd day of mouse embryo development. Postimplantation activity of hypoxanthine-guanine phosphoribosyltransferase parallels the weight of the embryo between Days 8 and 13. Preimplantation mouse embryos cultured in vitro have the same patterns of enzyme activity as do embryos developing in vivo, and changing environmental factors are not responsible for alterations in enzyme activity. Despite differences in the rate of development in vivo and in vitro, enzyme activity remains closely correlated with morphogenesis.