Evaluation of the expression of a male-specific antigen on cells of equine blastocysts.
This experiment was designed (1) to determine if H-Y antigen is expressed on the cell surface of pre-implantation equine blastocyst stage embryos, (2) if so, to identify differences in expression on inner cell mass (ICM) verses trophectoderm cells and (3) to evaluate whether the detection of this glycoprotein would aid in the identification of equine embryonic sex. A total of 33 blastocyst stage horse embryos were collected 6-7 days post-ovulation by trans-cervical flush and were immediately evaluated for the presence of H-Y antigen. Additionally, 17 embryos, collected at similar stages and cultured for 72 h, were similarly evaluated. Embryos were recovered and evaluated by use of a dissecting microscope and then washed for 5 min in phosphate buffered saline supplemented with 1 g/l glucose, 36 mg/l pyruvate, 1% antibiotic-antimycotic and 10% fetal calf serum (FCS) (PBS-2). Embryos were placed in the primary antibody medium and cultured for 60 min. The primary antibody medium consisted of monoclonal antibodies to H-Y antigen (previously determined to have male-specific activity) dilute 1/5 (v/v) with PBS-2 (without FCS, PBS-1). Following an additional wash, embryos were cultured in PBS-1 containing 1/10 (v/v) fluorescein isothiocyanate conjugated goat anti-mouse or rabbit antimouse IgM Fc specific antiserum. Embryos were evaluated at 200-400 x to identify cell specific fluorescence of either trophectoderm or ICM cells. Following evaluation, embryonic sex was independently verified with karyotypes to identify sex chromosomes. Of the 50 embryos evaluated, 29 were evaluated as non-fluorescent and 21 fluorescent. Expression of H-Y antigen was detected on both trophectoderm and ICM cell types in those embryos classified as fluorescent.(ABSTRACT TRUNCATED AT 250 WORDS)