Expressions of TLR4, MyD88, IRAK4 and NF-κΒ in the oviduct of Chinese brown frog (Rana dybowskii)

One special physiological phenomenon of the Chinese brown frog (Rana dybowskii) is that its oviduct goes through expansion prior to pre-hibernation instead of expanding during the breeding period. Our previous study discovered that some cytokines such as interleukin-1 beta (IL-1β) and its receptor type I (IL1R1) proteins were expressed in the oviduct of Rana dybowskii. In this study, we continued to investigate the localizations and expression levels of cytokines including toll-like receptor 4 (TLR4) and its related factors, myeloid differentiation factor 88 (MyD88), interleukin-1 receptor-associated kinase (IRAK) and nuclear factor kappa B (NF-κΒ) in the oviduct of Rana dybowskii during the breeding period and pre-hibernation. Morphological results showed that there were significant differences in oviductal weight and pipe diameter with significantly higher values in pre-hibernation than those of the breeding period. Strong immunostaining of TLR4, MyD88, IRAK4 and NF-κΒ were observed in the pre-hibernation. These proteins levels had no significant difference between these two periods except MyD88 which was significantly higher in the pre-hibernation. The mRNA expression levels of MyD88 and NF-κΒ were obviously higher in pre-hibernation than those of the breeding period. These findings suggested that TLR4/MyD88 signal pathway might participate in the oviductal functions of Rana dybowskii during the breeding period and pre-hibernation.