Differential Neurotrophin-4 mRNA Expression in Reproductive Organs of Prepubertal Gilts with Different Dietary Energy Level
The development of reproductive system in prepubertal gilts was affected not only by gonadotropins but also by other cytokines and growth factors. Recent studies have revealed that Neurotrophins (NTs) which are well known for their essential roles in neural system also expressed in mammalian reproductive organs and involved in the regulation of mammalian reproduction. Dietary energy level is an important factor affecting domestic animal reproductive performance including central effects on Hypothalamic Pituitary Gonadal (HPG) axis and local effects on gonads. In the present study, the expression of Neurotrophin-4 (NT-4) which is a member of NTs in reproductive tissues of prepubertal gilts including ovary, oviduct and uterus was studied by immunohistochemistry. The effects of dietary energy on NT-4 mRNA expression were also investigated by quantitative PCR. The results show that NT-4 was localized in all classes of follicles in ovaries of prepubertal gilts including primordial follicles, primary follicles and secondary follicles, NT-4 was localized in mucosal epithelial cells in oviducts and glandular epithelium and endometrial epithelium in uteri. Furthermore, different dietary energy levels altered mRNA expression level of NT-4 in ovaries, uteri and oviducts of prepubertal gilts. NT-4 mRNA expression level in ovaries and uteri was higher in high dietary energy group than that in mid and low-energy groups. In oviduct, the expression pattern of NT-4 mRNA among three different dietary energy groups is similar as that occurred in in ovaries and uteri but with more significant differences. These results suggest that NT-4 may be one of the signals that links metabolic status and neuroendocrine control of reproduction in pig.