DIRECT VS INDIRECT EFFECTS OF TRYPAN BLUE ON THE ECTODERMAL CELLS OF THE 11.5-DAY RAT EMBRYO

The effect of trypan blue on the 11.5-day rat conceptus after intravit elline vessel administration is described. For comparison, conceptuses injected with varying volumes of Hanks' BSS have also been studied. T rypan blue significantly retarded the growth and development of concep tuses after 6 hours incubation in vitro. The SEM revealed rounded ecto dermal cells, some of which appeared disrupted. These cells seemed to cause some of the intersomitic grooves to disappear, making a number o f the somites indistinct from the outside. Unlike cells of uninjected embryos, the surfaces of the affected ectodermal cells lacked microvil li and their perimeters were lined with microvilli-like structures whi ch appeared matted together. It was concluded that trypan blue affecte d the embryo directly probably by disturbing its fluid and ionic balan ce.