Lower sodium lactate in Whitten's medium improves in vitro developmental capacity of one-cell mouse embryos

A modification of Whitten's medium, involving a reduced content of Na-lactate syrup (0.2 ml/100 ml; 11.65 mM) and osmolarity (251 mOsm), was compared with normal Whitten's medium (0.37 ml/100 ml; 21.6 mM) for ability to support mouse embryonic development in vitro from one-cell to the blastocyst stage. In a pilot study utilizing 10 ICR donor female mice, in vitro developmental capacity (IVDC; percentage of fertilized one-cell embryos developing to blastocysts in vitro per female donor) was significantly enhanced by the modified medium (68.0 versus 24.0%; P<0.001). In the main study, utilizing 134 ICR and 17 ICR x C57BL/6J F(1) donor females, the modified medium supported increased IVDC for both ICR (67.9 versus 51.1%; P<0.001) and F(1) females (98.5 versus 89.4%; P<0.05). A large degree of among donor-female variation in IVDC was observed for both media in the ICR stock (SD = 30.0). The beneficial role of the reduction of Na-lactate in Whitten's medium may be related to an improved provision of energy requirements for first cleavage and/or a more suitable osmolarity for development.