Interaction between neurotrophin 4 and gonadotrophin in bovine oviducts

The expression and localization of neurotrophin 4 (NT4) and its receptor, tyrosine kinase B (TRKB), in the bovine oviduct, and their interaction with gonadotrophins in bovine oviduct epithelial cells (BOECs), were examined. Transcripts for NT4 and TRKB were detected by reverse transcription polymerase chain reaction (RT-PCR) in bovine oviducts in the follicular and luteal phases, and their proteins were immunolocalized in BOECs. Based on real time PCR, NT4 mRNA did not differ significantly between the two phases of the cycle, although TRKB mRNA expression was higher (P < 0.05) in the luteal phase than that in follicular phase. The BOECs were treated with various concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in vitro; for NT4, mRNA and protein were higher (P < 0.05) than those in the control (based on real time PCR and enzyme-linked immunosorbent assay (ELISA) assays). The effects of NT4 and the TRKB inhibitor (K252a) on the expression of LH receptor (LHR) and FSH receptor (FSHR) in the oviduct epithelial cells were also studied using a monolayer culture model. Expression levels of LHR and FSHR mRNA in BOECs treated with various concentrations of NT4 were higher (P < 0.05) than those in the control. However, these expressions were blocked by treatment with K252α. We concluded that neurotrophin 4 may have a role in regulating the function of bovine oviducts by interacting with gonadotrophins.