DEVELOPMENT OF PREIMPLANTATION GUINEA-PIG EMBRYOS IN SERUM-FREE MEDIA

This study was undertaken to determine how far preimplantation guinea- pig embryos can develop normally in vitro with serum-free media genera lly used for mouse (Whitten's medium, WM) and rabbit (Kane's medium, K M) embryos. Preimplantation guinea-pig embryos were recovered from nat urally mated females at each day of pregnancy between Day 1 and Day 6, and were cultured in vitro with either WM or KM at 37 degrees C in 5% CO2 in air. One-cell (Day 1) and 2-cell (early Day 2) embryos culture d in WM developed to the 4-cell and morulae stages respectively, where as the corresponding embryos cultured in KM arrested development at th e 2-cell and 8-cell stages respectively. In contrast, 4-cell (late Day 2 and Day 3) embryos proceeded to the blastocyst stage in KM, but not in WM. Eight-cell embryos (Day 4) and morulae (Day 5) developed to bl astocysts in either medium. However, hatching of the blastocysts and t rophoblast outgrowth on the culture dish were supported only by KM eve n when collected at the blastocyst stage. The present study suggests t hat, in guinea-pig embryos, a distinct change in nutritional requireme nts occurs around the time of the second cell division and that, unlik e in the mouse, trophoblast outgrowth in the guinea-pig requires no su pplementation of serum or extracellular matrices.