Park Jin Woo, Jin Ye Hwa, Oh Sung-Yong, Kwon Joon Yeong
Marine Ecosystem and Biological Research Center, Korea Institute Ocean Science & Technology, Ansan 15627, Republic of Korea.
Dept. of Aquatic Life Medical Sciences, Sunmoon University, Asan 31466, Republic of Korea.
Comp Biochem Physiol B Biochem Mol Biol. 2016 Dec;202:31-38. doi: 10.1016/j.cbpb.2016.07.009. Epub 2016 Aug 3.
It has been suggested that kisspeptin influences reproduction and onset of puberty in fishes. Unlike mammals, which produce only one kisspeptin (Kiss1), some teleosts have two, Kiss1 and Kiss2, both thought to be involved in the stimulation of gonadotropin (GTH) secretion. In Nile tilapia (Oreochromis niloticus), however, only Kiss2 has been identified so far. The effect of Kiss2 on GTH release varies significantly depending on species and reproductive stage. Furthermore, its physiological function in this species is not clearly defined. In this study, kiss2 gene expression profiles were examined using quantitative real-time PCR (qRT-PCR) in the brain, pituitary, and gonads of Nile tilapia at different reproductive stages (male: immature, pre-spermiation, post-spermiation; female: immature, pre-spawning, post-spawning). The kiss2 mRNA expression profiles of the brain, pituitary, and gonads of both sexes shared a similar pattern their expression was significantly higher at the immature stage than at the mature or post-spawning stages, implying it is involved in early gonadal maturation in this species. To investigate the effect of kisspeptin on the hypothalamus-pituitary-gonad (HPG) axis in vivo, synthetic kisspeptin2 (FNYNPLSLRF) was injected into immature male and female tilapia intraperitoneally (i.p.) at a dose of 200pmol/g body weight. The results showed that synthetic Kiss2 administration increased the expression of GnRH I, fshβ and lhβ mRNA in the brain and increased 17β-estradiol (E) and 11-ketotestosterone (11-KT) levels in the plasma. These results suggest that Kiss2 stimulates the expression of GnRH and GTH genes in immature Nile tilapia.
有人提出，亲吻素会影响鱼类的繁殖和青春期的开始。与只产生一种亲吻素（Kiss1）的哺乳动物不同，一些硬骨鱼有两种亲吻素，即Kiss1和Kiss2，它们都被认为参与了促性腺激素（GTH）分泌的刺激过程。然而，在尼罗罗非鱼（尼罗口孵非鲫）中，到目前为止只鉴定出了Kiss2。Kiss2对GTH释放的影响因物种和生殖阶段的不同而有显著差异。此外，它在该物种中的生理功能尚未明确界定。在本研究中，使用定量实时PCR（qRT-PCR）检测了尼罗罗非鱼在不同生殖阶段（雄性：未成熟、精子发生前期、精子发生后期；雌性：未成熟、产卵前期、产卵后期）的脑、垂体和性腺中kiss2基因的表达谱。雌雄两性的脑、垂体和性腺中kiss2 mRNA的表达谱呈现出相似的模式——它们在未成熟阶段的表达显著高于成熟或产卵后期，这意味着它参与了该物种早期性腺的成熟过程。为了研究亲吻素在体内对下丘脑-垂体-性腺（HPG）轴的影响，以200pmol/g体重的剂量将合成的亲吻素2（FNYNPLSLRF）腹腔内（i.p.）注射到未成熟的雄性和雌性罗非鱼体内。结果表明，给予合成的Kiss2可增加脑中GnRH I、fshβ和lhβ mRNA的表达，并提高血浆中17β-雌二醇（E）和11-酮睾酮（11-KT）的水平。这些结果表明，Kiss2可刺激未成熟尼罗罗非鱼中GnRH和GTH基因的表达。
