Evidence that glucose is not always an inhibitor of mouse preimplantation development in vitro

A factorial experimental design was used to examine the effects of 16 combinations of four concentrations of glucose (0.20, 0.60, 1.8, 5.4 mmol/l) and four concentrations of potassium dihydrogen phosphate (KH(2)PO(4); 0.05, 0.15, 0.45, 1.35 mmol/l) on the development in vitro of outbred CF1 mouse zygotes. Three responses were measured: (i) the number of zona-enclosed blastocysts; (ii) the number of blastocysts that started to hatch; and (iii) the total cell counts in the blastocysts. General linear modelling was used to estimate the most parsimonious two-dimensional concentration-response surfaces that represent the three responses to the different concentrations of glucose and KH(2)PO(4). There were no significant interactions between the effects of glucose and KH(2)PO(4) in all cases. Thus, the effects of glucose and phosphate are independent. No significant effects of glucose on blastocyst formation and the initiation of hatching were observed. Increasing the concentration of KH(2)PO(4) inhibited slightly (less than or equal to 20%) the development of zygotes into blastocysts and the initiation of hatching. The slight inhibitory effects of KH(2)PO(4) appeared to be due to the inhibition of the development of a few sensitive embryos. No significant effects of glucose and KH(2)PO(4) were observed on the total cell counts.