Expression of Progesterone Receptor in the Utero-tubal Junction after Intra-uterine Insemination in Sows

Introduction Recently, a new procedure for intrauterine insemination (IUI) in sows has been established (1,2). The procedure consists of a specially designed catheter that can be passed through the cervix allowing the deposition of sperm in the uterus. Using this technique, the number of spermatozoa per dose can be reduced by up to 1 billion spermatozoa. It has been demonstrated that the IUI technique with a 3-times reduction in the sperm number per dose resulted in the same conception rate and litter size, under farm conditions, as conventional artificial insemination (AI) (1). However, Rozeboom et al. (3) found that IUI with ≤1 x 10 spermatozoa per dose resulted in a smaller litter size compared to a conventional AI with 4x10 spermatozoa per dose. The mechanism of sperm transport from the insemination site to the fertilization area is complex and is regulated by many factors involving both the female genital tract and the spermatozoa (4). Additionally, ovulation has been postulated to affect sperm transport by initiating the redistribution of spermatozoa from the sperm reservoirs. This redistribution may be regulated by a change in the hormonal profile that occurs during ovulation (4, 5). Sperm distribution and fertilization after IUI with a reduced number of spermatozoa have been demonstrated (2). Progesterone (P4) significantly increased soon after ovulation in pig and influences the transportation of spermatozoa and embryos (5). The mechanism of P4 on sperm transportation in the female reproductive tracts is related the expression of progesterone receptor (PR) in the uterine horn and the oviduct of pig (6). It is well established that estrogen (E2) up-regulated PR and P4 downregulates PR (6). PR was higher in inseminated sows compared to cyclic sows (6) The immunostaining of PR in the uterus was high during 5-6 h to 70 h after insemination (6). The expression of PR after IUI in pig has never been investigated. The present study was performed to investigate the expression of PR in the utero-tubal junction of sows at 24 h after IUI compared with conventional AI.