CHANGES IN ENZYMES OF CARBOHYDRATE METABOLISM IN RAT UTERUS DURING EARLY PREGNANCY

Abstract

ABSTRACT The enzymes phosphofructokinase (PFK), pyruvate kinase (PK), isocitric dehydrogenase (ICDH), malic dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G-6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) have been measured in rat uterus during the first 9 days of pregnancy. It was found that after implantation on day 6, the activities of PFK and PK (the key glycolytic enzymes) increased in terms of dry weight — and in terms of protein in the implantation sites, but decreased in non-implanted tissue. The pentose shunt enzymes changed similarly to those of the glycolytic enzymes. ICDH activity increased in the non-implanted tissue and decreased in the implanted tissue. Changes in malic dehydrogenase were extremely variable and did not show a consistent pattern. Administration of Actinomycin D on day 6 of pregnancy abolished the increase in PK and PFK in the implantation sites and indeed led to a major decrease in activity. This implies that the increased PK and PFK in the implantation sites, arise from a DNA dependent RNA directed synthesis of new enzyme protein. The results are discussed in relation to the energy requirement of the decidualising tissue and the need for increased pentose for RNA synthesis. It is suggested that the extra NADPH resulting from the pentose shunt is involved in increased lipid synthesis.