Impact of gonadotrophin dose on pre-embryo recovery and development in superovulated mice.

A dose-response analysis was performed by stimulating mice with Humegon, which contains approximately equal amounts of follicle stimulating hormone (FSH) and luteinizing hormone (LH). The effect of increasing stimulation was assessed by monitoring the number and developmental stages of pre-embryos flushed from the tubes, and the developmental potency of these pre-embryos after culturing for 72 h. Increasing the stimulation doses resulted in an increased recovery of 2-cell pre-embryos. A maximal plateau of 40-50 2-cell pre-embryos was reached after stimulation with 15-30 IU FSH/LH. Higher stimulation doses up to 50 IU FSH/LH showed no further increase in pre-embryo recovery. Increased stimulation doses did not affect the number of 1-cell pre-embryos or the number of pre-embryos which developed further than the 2-cell stage. An average of 88 +/- 1.7% of the flushed pre-embryos were 2-cell pre-embryos. The fraction of flushed pre-embryos which developed into blastocysts after 72 h of culturing was constant at all stimulation doses, with an average of 81 +/- 1.9%. A maximal plateau of 35-40 blastocysts was reached after stimulating with 15-30 IU FSH/LH. The group of pre-embryos at less advanced developmental stages and the group of degenerated pre-embryos showed a small but dose dependent increase in number. In conclusion, we found that increasing doses of Humegon resulted in an increased recovery of pre-embryos capable of preimplantation development. This increased recovery occurred despite the high level of LH contained in this FSH/LH stimulation.