Abstract
It is well known that hamster embryos cannot complete the second cleavage division in vitro (2-cell block), if cultured in glucose and inorganic phosphate (Glu/Pi) containing medium. It is unclear how the block to development in vitro is caused in the presence of Glu/Pi. In the present study, the ATP in hamster embryos at the 2-cell block in M199 supplemented with 5% heated calf serum was examined and compared to the ATP in 2-cell embryos just recovered from oviducts and preimplantation hamster embryos developing in vitro from 2-cell to blastocyst stages in Glu/Pi-free medium (HECM3). ATP in hamster embryos was measured by an ATP-dependent luciferin - luciferase bioluminescence assay. The average ATP content and SEM was 44.5 ± 7.4 fmol/embryo at the 2-cell stage, 13.1 ± 1.2 fmol/embryo at the 4-cell stage, 72.3 ± 21.0 fmol/embryo at the 8-cell stage and 22.7 ± 6.6 fmol/embryo at the blastocyst stage. A significant decrease in ATP content was observed at the 4-cell stage and blastocyst stage as compared to the 8-cell stage (P<0.05). The other hand, the average amount of ATP and SEM in the 2-cell block embryos was 98.3 ± 17.1 fmol/embryo and was much higher than that in the preimplantaion embryos developing in vitro. We therefore suggest that the 2-cell block of hamster embryos may be due, in part to the high ATP content, that is, low levels of cytochrome activity and low levels of ATP synthesis.
