Effect of follicle-stimulating hormone on ZPC protein secretion by quail granulosa layer

In avian species, ZPC, a glycoprotein of the inner layer of the vitelline membrane, is synthesized in the granulosa cells of developing follicles. We have previously reported that follicle‐stimulating hormone (FSH) is one of the factors that stimulate ZPC production in quails. In the present study, we examined the effect of FSH on ZPC secretion, and the mode of ZPC secretion from pieces of granulosa layer. Western blot analysis demonstrated that, in the absence of FSH, the intensity of ZPC bands in the medium faded after 6 h of incubation. The addition of FSH caused an increase in intensity of ZPC bands when incubated for more than 6 h. The ZPC secretion during the first 6 h of incubation was depressed by the addition of either cycloheximide or actinomycin D. These results show that the ZPC found in the medium during short‐term incubation is newly synthesized protein and is secreted from the granulosa cells by the constitutive secretory pathway.