Estradiol and progesterone affect enzymes but not glucose consumption in a mink uterine cell line (GMMe)

Cells lining the uterus are responsible for storage and secretion of carbohydrates to support early embryonic development. Histotrophic secretions contain glycogen and glycolytic products such as lactate and pyruvate. Insufficient carbohydrate storage as glycogen has been correlated with infertility in women. While it is clear that changes in estrogen (17-β-estradiol (E(2))) and progesterone (P(4)) in vivo affect the distribution of glucose in the uterine cells and secretions, the biochemical mechanism(s) by which they affect this crucial allocation is not well understood. Furthermore, in cultured uterine cells, neither E(2) nor P(4) affect glycogen storage without insulin present. We hypothesized that P(4) and E(2) alone affect the activity of glycolytic enzymes, glucose and glycolytic flux to increase glycogen storage (E(2)) and catabolism (P(4)) and increase pyruvate and lactate levels in culture. We measured the rate of glucose uptake and glycolysis in a mink immortalized epithelial cell line (GMMe) after 24-h exposure to 10 μM P(4) and 10 nM E(2) (pharmacologic levels) at 5 mM glucose and determined the kinetic parameters (V(max), K(m)) of all enzymes. While the activities of many glycolytic enzymes in GMMe cells were shown to be decreased by E(2) treatment, in contrast, glucose uptake, glycolytic flux and metabolites levels were not affected by the treatments. The cellular rationale for P(4)- and E(2)-induced decreases in the activity of enzymes may be to prime the system for other regulators such as insulin. In vivo, E(2) and P(4) may be necessary but not sufficient signals for uterine cycle carbohydrate allocation.