Immunohistochemical Localization of Luteinizing Hormone Receptor in the Cyclic Gilt Ovary

Luteinizing hormone receptor (LHR) is a specific membrane receptor on the granulosa and theca cells that bind to luteinizing hormone (LH), resulting in androgen and progesterone production. Hence, the regulation of LHR expression is necessary for follicle maturation, ovulation and corpus luteum formation. We examined the immunolocalization of LHR in cyclic gilt ovaries. The ovaries were obtained from 21 gilts aged 326.0 ± 38.7 days and weighing 154.6 ± 15.7 kg. The ovarian tissues were incubated with rabbit anti-LHR polyclonal antibody. The follicles were categorized as primordial, primary, preantral and antral follicles. Ovarian phase was categorized as either follicular or luteal phases. The immunolocalization of LHR was clearly expressed in primary, preantral and antral follicles. LHR immunostaining was detected in the cytoplasm of granulosa, theca interna and luteal cells. LHR immunostaining was evaluated using imaging software. LHR immunostaining in the theca interna cells in antral follicles was almost twice as intense as that in preantral follicles (65.4% versus 38.3%, P < 0.01). LHR immunostaining was higher in the follicular phase than in the luteal phase (58.6% versus 45.2%, P < 0.05). In conclusion, the expression of LHR in the theca interna cells of antral follicles in the follicular phase was higher than in the luteal phase. The expression of LHR in all types of the follicles indicates that LHR may impact follicular development from the primary follicle stage onwards.