Expression Profile of Luteinizing Hormone Receptor Gene in Hierarchal Follicles and Regressing Oviduct Tissues of White Leghorn Hens During Moulting R Agarwal 1 , KVH Sastry 1 , V Tripathi 2 , R Singh 1 , R Saxena 1 , J Mohan 1 and RP Singh 1,3 1 Physiology and Reproduction Division, Central Avian Research Institute, Izatnagar, Bareilly, India; 2 Department of Animal Science, M. J. P. Rohilkhand University, Bareilly, India; 3 Avian Physiology and Genetics Division, Salim Ali Centre for Ornithology and Natural History, Anaikatty, Coimbatore, India Contents In the present study, the expression profile of luteinizing hormone receptor (LHR) was investigated in the ovary, magnum and uterus and in hierarchcal follicles (F-1, F-2, F-3 and F-4) of hens subjected to moulting to establish their involvement in moulting and presence in non-gonadal tissues. Fifty-two layers (72 weeks) were subjected to moult for a period of 14 days. Four birds were sacrificed each time on 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12 and 14 days of moulting, and samples (ovary, magnum, uterus and hierarchal folli- cles) were collected aseptically for the quantitative study by real-time polymerase chain reaction. The ovary, isthmus, uterus and magnum weight reduced significantly during induced moulting. From the 4 DOM, this reduction was drastic and reached approximately 80% of original weight in the case of ovary, isthmus and magnum and approximately 65% of original weight in the case of uterus on 14 DOM. Ovarian yellow follicles decreased gradually from 1 DOM to 4 DOM, after that no normal yellow follicle was observed in moulted bird. The number of atretic follicles increased gradually during the course of induced moulting, reaching the peak at 5 DOM. The LHR mRNA was detected in non- gonadal tissues like magnum and uterus. The LHR expres- sion was significantly (p < 0.05) down regulated in ovary, magnum and uterus throughout the treatment. These results indicated that LHR may have a role in reproductive tissue regression during moulting. Introduction Moulting in avian species may be generally defined as the periodic shedding and replacement of feathers. In this physiological event, birds substantially reduce their feed intake and cease egg production. During moult- ing, the reproductive system of birds undergoes com- plete remodelling, that is, regression and regeneration. In the jungle fowl (Gallus gallus), the wild progenitor of the laying hen, establishment of broodiness appears to be the primary initiating factor for moulting. With the onset of broodiness, the jungle fowl hen experi- ences involution of the reproductive organs, a halt to egg laying and, eventually, the shedding and replace- ment of feathers (Sherry et al. 1980). The broody jungle fowl hen exhibits a voluntary reduction in food intake, which has been referred to as spontaneous anorexia (Mrosovsky and Sherry 1980). The hen loses approximately 20% of her body weight, and approx- imately half the bodyweight loss is owing to involution of the reproductive organs (Sherry et al. 1980). Many bird species, including the chicken, survive with little or no food for relatively long periods of time during moulting is a normal feature of their physiology. The physiological phenomena associated with moulting of feathers and remodelling of reproductive system is less understood. Reproductive remodelling appears to be a complex physiological mechanism involving endocrine, reproductive and immune systems (Berry 2003). In chickens, regression of the ovary and oviduct during moulting is achieved through apoptosis that is induced mainly by the withdrawal of oestrogen and progesterone (Bell 2003; Anish et al. 2008; Sun- daresan et al. 2008). During moulting, the pituitary response to luteinizing hormone–releasing hormone (LHRH) for the secretion of LH is reduced (Kawa- shima et al. 1992) which may result in inhibition of gonadotrophin-sensitive steroidogenesis in hens. Absence ⁄ inhibition of sex steroids leads to the regres- sion of oviduct through up regulation of pro-apopto- tic genes like caspases-1 and caspases-2 (Anish et al. 2008). Besides, decreased circulating levels of luteiniz- ing hormone were reported during moulting (Dicker- man and Bahr 1989) which might be responsible for the regression in ovary. However, there have been conflicting reports about the role of LH in the reproductive tissue regression in mammals. Yacobi et al. (2004) reported that LH enhances caspase activity and apoptosis in the theca-interstitial cells of rat pre-ovulatory follicles in culture. In contrast to this, Slot et al. (2006) reported that LH protects ovarian cells against Fas-induced apoptosis through a signalling cascade involving PKA. Our previous results also suggested that the presence of two different pathways that are responsible for reproductive tissue regression during moulting (Anish et al. 2008). We hypothesized that the LHR expression varies accord- ing to tissue owing to involvement of different apoptotic pathways. Therefore, we investigated the expression of LH receptor in the regressing reproduc- tive tissues during moulting. The luteinizing hormone receptor (LHR) has been classically described as a receptor present in gonads (ovary and testis) controlling various reproductive processes. However, recent evidences suggest the pres- ence of LHR in the extragonadal tissue, particularly in the female reproductive tract of human, bovine, porcine, rat, mouse, rabbit and turkey (Mukherjee et al. 1994; Friedman et al. 1995; You et al. 2000). However, to the best of our knowledge, there is no information regarding the expression of this receptor in the oviduct of hens. Therefore, LHR expression in the oviduct and its role during moulting was examined in the present investigation. Reprod Dom Anim doi: 10.1111/j.1439-0531.2012.02145.x ISSN 0936-6768 Ó 2012 Blackwell Verlag GmbH