ENZYMES OF PURINE SALVAGE AND CATABOLISM IN THE MOUSE PREIMPLANTATIONEMBRYO MEASURED BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The activities of five enzymes involved in purine salvage and cataboli sm - hypoxanthine phosphoribosyl transferase (HPRT), adenine phosphori bosyl transferase (APRT), adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP) and guanase - were measured in mouse embryo extra cts, from the one-cell to the blastocyst stage. Xanthine oxidase activ ity was not detected. The analyses were performed using high performan ce liquid chromatography and the enzymes showed different patterns of activity during development. Activities of HPRT, APRT and PNP were low before morula formation, and then increased until the blastocyst stag e. ADA and guanase showed high activities after fertilization; guanase activity decreased sharply after the two-cell stage and ADA activity decreased sharply after the morula stage. Blastocyst formation was acc ompanied by a further decline in activity of both enzymes. The methods used may be suitable for measuring these enzymes in single human embr yos, or in biopsies derived from them.