CARBOHYDRATE UPTAKE BY QUIESCENT AND REACTIVATED MOUSE BLASTOCYSTS

The mouse, Mus musculus, can maintain blastocysts in embryonic diapaus e in the uterus while suckling young. This study used microfluorimetry to simultaneously examine glucose and pyruvate uptake by quiescent bl astocysts, and at four hourly intervals after administration of the re activating stimulus, oestradiol-17 beta. Following the non-invasive an alysis of energy metabolism, blastocysts were incubated in colcemid (0 .2 mg/ml), and mitotic activity determined. Mitoses and cell numbers i n reactivated embryos increased significantly within 8 and 12 hours, r espectively, after oestradiol-17 beta administration, compared to thos e of diapause (control) blastocysts (0.5 +/- 0.1 vs. 0.22 +/- 0.03 mit oses/embryo; P < 0.05, and 141.8 +/- 1.5 vs. 133.8 +/- 2.4 cells/embry o; P < 0.05). Similarly, pyruvate uptake by reactivating blastocysts ( 9.3 +/- 1.1) was significantly higher than controls (5.8 +/- 0.8 pmol/ embryo/hour; P < 0.05), within 4 hours of oestradiol-17 beta, but by 1 6 hours after oestradiol-17 beta administration, pyruvate uptake by re activating blastocysts was no longer significantly different from the delayed controls. In contrast, significant differences in glucose upta ke between the reactivated and control groups were not evident until 1 6 hours after oestradiol-17 beta (reactivating, 14.9 +/- 1.5; control, 10.6 +/- 1.7 pmol/embryo/hour; P < 0.05). These results demonstrate t hat pyruvate rather than glucose could supply the additional energy re quired during the first 12 hours of reactivation in the mouse, but fro m 16 hours after injection of the reactivating stimulus oestradiol-17 beta, glucose is the predominant energy source. (C) 1996 Wiley-Liss, I nc.