DIFFERENTIAL EXPRESSION OF ZPC IN THE BOVINE OVARY, OOCYTE, AND EMBRYO

Using nonradioactive in situ hybridization (ISH), the mRNA encoding th e zona glycoprotein bZPC was localized in bovine ovaries, oocytes, and embryos. In the ovary, the distribution of the mRNA was correlated wi th the developmental stage of the follicle. Whereas in primordial and primary follicles the mRNA was predominantly seen in the oocyte, it wa s found in both the oocyte and the follicle cells of secondary and ter tiary follicles. In 2-day-old embryos produced by in vitro fertilizati on (IVF), no mRNA encoding ZPC could be demonstrated. Immunoblotting u sing monospecific polyclonal antibodies against porcine ZPC revealed a distinct band at a molecular weight of 47 kD in the ovarian cortex of cows, calves, and fetuses as well as in bovine follicle cells. Immuno histochemistry using the ZPC antibody displayed a strong signal in the zona pellucida of bovine oocytes and 2- to 6-day-old embryos as well as in the follicle cells. Our results show that during follicular deve lopment bovine ZPC is synthesized by the oocyte of the primary follicl e and by both the oocyte and the follicle cells of the secondary and t ertiary follicle. After fertilization, the synthesis of the zona prote in is finished. (C) 1998 Wiley-Liss, Inc.