Effect of growth factors in culture medium on the rate of mouse embryo development and viability in vitro.

The development of mouse embryos from two cells to blastocysts in Whittingham's T6 medium containing the growth factor insulin or the serum replacement Nu-Serum was studied and compared with development in vivo. The rate of embryo development to blastocysts was increased by the addition of Nu-Serum to T6 and there was a significant increase in the implantation rate of embryos grown in T6 + Nu-Serum compared with T6 alone or with insulin. However, the rate of embryo development in vitro was retarded compared with that in vivo and the number of normal fetuses following transfer to recipients of blastocysts grown in T6 + Nu-Serum was not different from the number for those grown in T6 alone or with insulin. The addition of neither insulin nor Nu-Serum to T6 optimizes embryo development or viability.