Dihydrofolate Reductase in Starfish Oocytes and Embryos: Developmental Consequences of Its Inhibition by Methotrexate : (starfish/dihydrofolate reductase/methotrexate/DNA synthesis/early development).

Dihydrofolate reductase in immature oocytes of the starfish, Asterina pectinifera, is estimated to be 12 pg per oocyte. After completion of meiosis, the quantity of the enzyme is approximately 20 pg per egg. The content of the enzyme in the egg is kept nearly constant at this value from fertilization to the beginning of blastulation.