ENERGY-METABOLISM OF THE TROPHECTODERM AND INNER CELL MASS OF THE MOUSE BLASTOCYST

The two cell populations of the day 5 mouse blastocyst-the inner cell mass (ICM) and trophectoderm (TE)-were isolated by immunosurgery and T E biopsy. The uptake of glucose and pyruvate and the production of lac tate were measured in the isolated cell populations and in single day 5 blastocysts, using a non-invasive ultramicrofluorescence technique. The number of cells in isolated ICMs, TE vesicles, and intact blastocy sts were counted after differential labeling with fluorochromes. The u ptake of glucose and the formation of lactate were approximately three and five times greater, respectively, in the ICM cells compared with the TE cells. All the glucose consumed by the ICM could be accounted f or by lactate formation, whereas the value for TE was 55%. The uptake of pyruvate was low in both cell types. The results are consistent wit h the proposition that the TE acts as a transporting epithelium, spari ng nutrients for metabolism by the ICM. (C) 1993 Wiley-Liss, Inc.