Carbohydrate metabolism in 'delayed implanting' mouse blastocysts undergoing activation in utero and in vitro

Delayed blastocysts were activated by injecting oestradiol-17 beta to delayed implanting mice or by exposure to culture medium lacking serum. Four enzymes of carbohydrate metabolism (phosphofructokinase, pyruvate kinase, lactate dehydrogenase, malate dehydrogenase) were studied at different time periods and specific time-dependent changes were found during activation. A characteristic feature was a marked decline by 6 h in the activities of phosphofructokinase and pyruvate kinase. Blastocyst activation in vitro and in utero showed similar trends in metabolic patterns during the 24-h period studied.