Following the insertion of copper wire into their uterine horns, rabbits were mated and cytochemical and ultrastructural observations carried out on blastocysts and on the left (control) and right (treated) horns of the pregnant uteri. The blastocysts and uterine tissue from the control horns were normal in all respects. Blastocysts obtained from the treated horns on Day 6 of gestation contained numerous membrane-bound vacuoles, identified as lysosomes by acid-phosphatase staining, that contained amorphous material in which the presence of copper was revealed by the rubeanic acid procedure. No blastocysts were recovered from treated horns after Day 6.
Significant changes were observed in lysosomes of uterine epithelial cells on Days 6 to 10 of gestation. The effects were localized to the segment of uterus containing the copper wire and involved uptake of copper, autophagy, formation of myeloid bodies and shedding of epithelial cells containing such structures into the uterine lumen.
There was evidence to suggest that the entry of copper into blastocyst lysosomes was followed by release of lysosomal enzymes, cellular autolysis and death of the affected cells. In the uterus, the toxic effects of copper appeared to be confined to the epithelial cells, whose detachment from the mucosal surface may constitute a protective mechanism. The early effect of copper on the blastocyst suggests that this is the primary site of action of the metal.