Promoting Effect of IGF-I on Prehierarchical Follicle Development in Laying Chickens

【Objective】The aim of the experiment is to investigate the effect of IGF-I on prehierarchical follicle development from laying chickens.【Method】IGF-I receptor(IGF-IR) expression in granulosa and theca cells was studied in the prehierarchical follicles of laying chickens via immunohistochemistry and RT-PCR.In addition,the effects of IGF-I on small yellow follicle(SYF) development were investigated.【Result】The expression of IGF-IR gradually increased in both granulosa and theca layers from the prehierarchical follicles.Moreover,IGF-IR displayed the highest expression in SYF.Compared with control,treatment with IGF-I and FSH alone or in combination significantly increased cell density,thickness of granulosa and theca layers,stimulated the expression IGF-IR in both granulosa and theca layer from SYF.Furthermore,IGF-I and FSH displayed an additive effect.【Conclusion】 These results indicate that IGF-I may increase follicular cell number,thickness of granulosa and theca layers and stimulated IGF-IR mRNA expression in SYF.In addition,IGF-I exhibited synergistic effect with FSH to enhance prehierarchical follicular cell proliferation.Therefore,these results may facilitate delineating the mechanism of intra-ovarian endocrine regulation of poultry follicle development.