The expression of growth hormone (GH) receptors depends on numerous factors, including ontogenetic and endocrine ones. In domestic hens (Gallus domesticus), a short-term increase in the blood levels of reproductive hormones observed in each ovulatory cycle causes a rise in the concentration of GH receptors in the granulosa layer of hierarchical follicles. However, it remains unclear whether this change is related to an increase in the content of the corresponding mRNA. We performed a comparative study of the expression of the GH receptor gene (GHR) in granulosa and theca cells of two largest preovulatory follicles F1 and F2 at different stages of the ovulatory cycle depending on the hen age and reproductive aging. Three groups of birds were used in experiments: young hens with long egg clutches (YLC), old hens with long clutches (OLC), and old hens with short clutches (OSC). The expression level of the GHR gene in follicular cells was assessed by the content of the GH receptor mRNA, which was determined by real-time reverse transcription-PCR, followed by the data analysis using the 2–ΔΔCt method. A significant rise (p 0.05) in the content of the studied mRNA in granulosa cells from the largest hierarchical follicle F1 was found in OLC hens during the preovulatory hormonal surge, compared to the middle of the ovulatory cycle. These birds also showed a higher (p 0.001–0.01) expression of GHR in the granulosa layer of F1 and F2 follicles at both stages of the ovulatory cycle compared with YLC and OSC groups. In addition, in OLC hens, the hormone preovulatory surge increased (p 0.01) the relative level of GH receptor mRNA in theca cells of F2 follicles. Concurrently, the highest content of GHR transcripts in the thecal layer of F2 follicles was observed in YLC hens in the middle of the ovulatory cycle and in OLC hens during the preovulatory surge (p 0.01–0.05). The findings suggest that the increase in the GHR gene expression in granulosa cells of large hierarchical follicles, especially under the influence of the preovulatory surge of reproductive hormones on F1 follicles, may have a compensatory significance for maintaining a high egg laying intensity in aged hens.
Smekalova et al. (Thu,) studied this question.