NGF systems is differentially expressed in the ovary, oviduct and uterus of rabbit does although independent of serum hormonal levels

Abstract

Both NGF and its receptors (TrkA and p75) have been demonstrated to be present in the female tract of some species. Our goal was to study if NGF and its receptors showed a differential expression in the reproductive tract in follicular (FP) and luteal phase (LP) and its relationship with blood estradiol (E2), progesterone (P4) and NGF serum concentrations in rabbit females. Ovary, uterus and oviduct of eCG treated animals were removed 48 h later (FP) or 7 days after GnRH injection (LP) and fixed. Blood samples were recovered at the same points and hormones determined by ELISA. Immunohistochemistry of paraffined samples with the ABC method was performed for NGF, TrkA and p75. NGF was expressed in oocytes of smaller follicles, and in granulose and theca cells in secondary follicles, stronger stained in the LF. Corpus luteum (CL) showed strong immunoreaction. Both oviduct and uterus expressed NGF in both phases. TrkA was highly expressed in all the structures studied, slightly more intense in the LP. However, p75 only was found in secondary and preantral follicles in the vascular layer between the thecas, and in the CL. Signal in the uterus and oviduct was scarce. Vessels were very immunoreactive for all the NGF system. Similar levels of E2 were found in both phases (44.85 ± 8.2 vs.45.70 ± 6.02 pg/ml) whereas P4 concentration was higher in the LF (0.67 ± 0.11 vs.22. 28 ± 3.73 ng/ ml; p < 0.05). NGF concentration was maintained during the cycle (345.42 ± 77.45 vs.301.72 ± 69.66 pg/ml) and no correlation was found with serum steroid levels. In conclusion, NGF system seems to have an important role during both phases in the rabbit female tract and is independent of hormonal environment. (Funds by AGL2015-65572-C2-2-R Grant and Predoctoral Contract UCM-Santander.)