LIPID BIOSYNTHESIS IN AMPHIBIAN OOCYTE AND EMBRYONIC CELL-FREE PREPARATIONS

The utilization of [2-3H]glycerol-3-phosphate in the synthesis of lipids during early embryogenesis was studied in cell-free preparations from oocytes or embryos of Bufo arenarum Hensel. The precursor was incorporated in all stages of development up to gill circulation, which indicates that oocytes and embryos have the enzymatic machinery necessary to synthesize at least part of their own lipids. A significant decrease in the labeling of most lipids took place after fertilization, especially in gastrulas, but at gill circulation lipid synthesis was highly stimulated. The incorporation pattern is similar in unfertilized oocyte, fertilized oocyte and gastrulas, where phosphatidylglycerol has the highest amount of radioactivity. At gill circulation stage phosphatidylethanolamine and neutral lipid biosynthesis also became significant. A different regulation of the lipid biosynthetic routes through the appearance of new enzymes or modulators of preexisting enzymes during amphibian development is suggested.