Abstract
The zona pellucida is an extracellular glycocalyx that surrounds the growing oocyte and mediates specific biological functions essential to early mammalian development. We have isolated by a novel technique intact zonae pellucidae from a murine follicle culture system which mimics in vivo granulosa cell-oocyte interactions. Using radioactive precursors we have demonstrated that all three zona proteins, ZP-1, ZP-2, and ZP-3, are sulfated glycoproteins. Incubation of the follicle culture with tunicamycin (0.5 microgram/ml), an antibiotic that blocks N-glycosylation, inhibits new protein deposition in the zona. Under these same conditions overall protein synthesis is decreased only 30%. Biosynthetic studies indicate that after 6 days in culture the zona proteins are produced at 0.4 pg/oocyte/h, which represents 2-3% of the total oocyte protein synthesis. This synthesis stops at or before ovulation and the extremely long half-life (greater than 100 h) of the zona may be essential to preserve its known biological functions, all of which occur after ovulation.
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