[Expression of mRNAs for GHR, IGF-IR, FSHR and LHR in granulosa and theca layers of ovarian follicles of Shaoxing ducks].

Expression of genes encoding growth hormone receptor (GHR), type I insulin-like growth factor receptor (IGF-IR), follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) was measured in granulosa and theca layers of the largest (F1), third largest (F3), fifth largest (F5) preovulatory follicles and large white follicles (LWF) in the ovary of Shaoxing ducks, with relative quantitative reverse transcription-polymerase chain reaction (RT-PCR) using beta-actin as an internal standard. The results showed that GHR mRNA was more abundant in theca layer than in granulosa layer in all the follicles investigated, in theca layer, the LWF follicle expressed highest the level of GHR mRNA, while no differences in granulosa layer were observed among follicles at different stages of development. In contrast, the expression of IGF-IR mRNA in theca layer was evidently lower than that in granulosa layer, but no significant changes were found among different stages of follicles in either layers, except that LWF trended to express higher IGF-IR mRNA in the theca layer compared to other preovulatory follicles. Similar to IGF-IR mRNA, FSHR mRNA was more abundant in granulosa layer and no significant differences were found among different stages of follicles in either layers. In contrast, the expression of LHR mRNA followed a different pattern. In the theca layer, the expression level maintained consistent, while in the granulosa layer, a significant stepwise increase was observed as the follicles matured, resulting in higher mRNA level of LHR in the granulosa layer of largest follicles (F1), but lower mRNA level of LHR in the granulosa layer of smaller follicles (F5 and LWF). These results suggest that GH and IGF-I regulate ovary function by respective dominant sites in the follicles, and they cooperate with LH and FSH to regulate the follicle development via their respective receptors. The high expression of LHR mRNA in granulosa layer of large follicles might be related to the establishment of the follicle hierarchy and ovulation.