Sexing of rat embryos with antisera specific for male rats.

Male-specific antigenicity (H-Y antigen) of rat embryos has been examined, and the feasibility of sexing rat embryos by use of H-Y antibodies has been studied. Rat H-Y antisera were produced by immunization of female Wistar rats with a homogenate of testes from male Wistar neonates. Male specificity of the antiserum (H-Y antibody) was determined by retention of cytotoxicity to male epidermal cells after absorption with female cells. After cultivation of rat embryos for 5 to 6 hr in the presence of antibody, half of the embryos were arrested at the morula stage. However, these embryos developed into blastocysts after removal of the antiserum, and then they grew into male young in recipient foster mothers. Eighty percent of the embryos that developed to blastocysts in the presence of the antiserum grew into female young.