Expression of Anti-Müllerian Hormone and Its Type 2 Receptor in the Ovary of Pregnant and Cyclic Domestic Cats

SIMPLE SUMMARY: In female cats, AMH is secreted by ovarian follicles and exerts its effects via its specific receptor AMHRII. Its main function is regulation of cell proliferation and inhibition of excess recruitment of primordial follicles. Since the serum concentration is typically elevated in intact cats, multiple studies have investigated the usefulness of AMH measurement to assess intactness or for diagnosis of ovarian remnant syndrome. However, no study is available concerning the expression and regulation of AMH and AMHRII in feline ovaries. In this study, the site and degree of expression was investigated by using western blot and immunohistochemistry and related to follicle and corpora lutea number, as well as serum AMH concentration in estrus and interestrus cats, during different pregnancy stages. ABSTRACT: To evaluate the expression of AMH and its receptor AMHRII, ovaries of 33 p cats were investigated by western blot and immunohistochemistry. After ovariohysterectomy, the cats were grouped according to pregnancy stages and ovarian/placental endocrine activity: group I (n = 3, 24–29 days), II (n = 8, 32–40 days), III (n = 4, 41–46 days), IV (n = 6, 53–61 days) and according to cycle stages: V (n = 6, interestrus) and VI (n = 6, estrus). Serum progesterone- and AMH-concentration was measured. Follicle numbers did not differ between groups. The number of corpora lutea was higher in pregnant cats than in the non-pregnant cats. Serum AMH concentration was at maximum between day 30 and 50 of gestation, and was higher than in non-pregnant cats, then decreased towards term (p < 0.05). In the ovaries, AMH immunopositivity was observed in granulosa cells of secondary and antral follicles, and in interstitial cells of corpora lutea; highest percentage of immunopositive areas was detected in group III (p < 0.05). A positive correlation between the number of corpora lutea and the positive AMH signals in ovarian tissue was determined (r(2) = 0.832, p < 0.05); however, only during mid-gestation (group II). Expression of AMHRII was in close co-localization with AMH and strong in the interstitial cells surrounding follicles undergoing atresia. AMHRII expression did not differ between pregnant groups but was higher compared to estrus cats (p ˂ 0.05). We conclude that AMH and AMHRII expression in the feline ovary is comparable to other species. The high serum AMH concentration and ovarian AMHRII expression between day 30 and 50 of gestation are probably related to ovarian activity and follicular atresia.