Studies on the binding of antibody against mouse lactate dehydrogenase (isoenzyme X) by preimplantation mouse embryos

The binding of antibodies against LDH-X by preimplantation mouse embryos was studied to detect LDH-X from spermatozoa in embryos after fertilization. Incubation of preimplantation mouse embryos with rabbit anti-mouse-LDH-X-IgG and then with peroxidase-labelled goat anti-rabbit IgG revealed a strong peroxidase staining of the zona pellucida of normal fertilized and unfertilized 1-cell ova. However, the reaction was significantly weaker with both fertilized and unfertilized 1-cell ova from females induced to superovulate and normal and superovulated blastocysts. Pure antibody against mouse LDH-X was obtained by affinity chromatography of the rabbit anti-mouse LDH-X-IgG on pure mouse LDH-X covalently bound to sepharose. The pure antibody against mouse LDH-X reacted immunochemically identically to anti-mouse LDH-X-IgG, but it was not bound by any stage of preimplantation mouse embryos. The IgG fractions which had passed through the affinity column during the purification procedure and which did not contain any anti-LDH-X activity were bound by the zonae of preimplantation mouse embryos in the same manner as was unpurified anti-mouse LDH-X-IgG. Histochemical studies indicated LDH activity only in the embryo proper, but not on the zona pellucida. It is concluded that LDH-X is not present in preimplantation mouse embryos.