THE EFFECT OF OVARIECTOMY ON RABBIT BLASTOCYSTS

Abstract

SUMMARY: The behaviour of rabbit blastocysts and their uterine environment after ovariectomy was studied; the experimental period after ovariectomy varied from 17 to 26 hr. Most of the experiments were concerned with blastocysts recovered from rabbits spayed at 6 days; a few relate to embryos from animals spayed on day 5 or 7 of gestation. Ovariectomy resulted in variable, often considerable, embryonic loss. Following bilateral ovariectomy at 6–6½ days, implantation on day 7 was completely prevented; those blastocysts which survived showed evidence of expansion and differentiation during the interval after ovariectomy. This provided an opportunity (1) to assess the stage of development, and mitotic activity, as well as certain biochemical characteristics, in embryos surviving ovariectomy, and (2) to use the free-lying 7-day-old blastocysts for culture experiments. It was found that mitotic activity went on in blastocysts after ovariectomy. Upon transfer to suitable culture media the unimplanted 7-day-old blastocysts continued to grow and differentiate, the most advanced stage observed at the end of a 24 hr. period of incubation in vitro being the development of blood islands, primitive groove, and head process. The fresh weight, and the content of bicarbonate and glucose of the 7-day-old unimplanted blastocysts differed little from those of normally implanted blastocysts of the same age; their content of lactate, however, was distinctly lower. Carbonic anhydrase activity after spaying was fully maintained in the endometrium which showed little involutional change either on gross or on microscopical examination.