GH/IGF-Ⅰ轴对半滑舌鳎(Cynoglossus semilaevis)卵巢发育的调控作用

摘要

为深入认识半滑舌鳎(Cynoglossus semilaevis)生殖调控机制,研究了生长轴(GH/IGF-Ⅰ axis)对半滑舌鳎卵巢发育调控的作用及可能机制;分析了卵巢不同发育时期垂体中的生长激素(GH),脑、性腺和肝脏中的类胰岛素生长因子Ⅰ (IGF-Ⅰ)mRNA的表达水平变化;检测了卵巢不同发育期,血清GH、IGF-Ⅰ、雌二醇(E2)、睾酮(T)的表达水平变化,并分析了生长因子与性腺指数(GSI)、E2和T表达变化的关系.结果显示,垂体GH mRNA表达水平在Ⅳ期卵巢时显著升高,至Ⅴ期时达峰值,随后(Ⅵ期)显著降低,垂体GH mRNA表达水平与GSI、血清GH与IGF-Ⅰ表达水平呈显著正相关.血清GH与垂体GHmRNA表达水平表现出相似的变化趋势.肝脏IGF-ⅠmRNA表达水平在Ⅳ期和Ⅴ期卵巢时较低,但Ⅵ期时又显著升高,其与脑IGF-Ⅰ mRNA及血清IGF-Ⅰ表达水平呈显著正相关,而与血清E2和T表达水平呈显著负相关.脑IGF-Ⅰ mRNA表达水平自Ⅱ期卵巢开始显著升高,至Ⅳ期时达峰值,并与血清IGF-Ⅰ表达水平呈显著负相关.卵巢IGF-ⅠmRNA表达水平自Ⅱ期开始显著升高,并在Ⅳ期时达峰值,但在Ⅴ期时明显下降,并保持至Ⅵ期,与血清E2表达水平呈显著正相关,而与血清IGF-Ⅰ表达水平呈显著负相关.血清IGF-Ⅰ变化趋势与肝脏IGF-ⅠmRNA相似.结果揭示了GH、IGF-Ⅰ在转录和血清水平上以协同或者拮抗的方式共同参与了半滑舌鳎卵巢发育的过程,其作用途径可能与性类固醇激素的合成与分泌有关,表明GH/IGF-Ⅰ轴对卵巢发育具有重要的调控作用,为深入认识半滑舌鳎卵巢发育的调控机制提供了新的思路和素材.%In order to deeply understand underlying mechanisms for regulating reproductive trait of Cynoglossus semilaevis,the physiological role of GH/IGF-Ⅰ axis in ovarian development was explored.The levels of growth hormone (GH) mRNA of pituitary and IGF-Ⅰ mRNA of liver,brain,and ovary at different ovarian development stages were determined by quantitative real-time PCR (qRT-PCR) analysis.Meanwhile,the expression levels of serum GH,IGF-Ⅰ,estradiol (E2) and testosterone (T) were detected by radioimmunoassay (RIA) and ELISA methods,respectively.Furthermore,the correlation between the mRNA and peptides expression levels of GH,IGF-Ⅰ and gonadosomatic index (GSI),and the one between the expression levels of serum E2 and serum T during ovarian development was calculated with statistical methods.The results showed that,the levels of pituitary GH mRNA significantly increased at stage Ⅳ ovary,and peaked at stage Ⅴ ovary,but decreased significantly post spawning (stage Ⅵ).It has significantly positive relationship with the expression levels of GSI,serum GH and serum IGF-Ⅰ during ovarian development.The serum GH levels showed similar trend with pituitary GH mRNA expression levels.Liver IGF-Ⅰ mRNA achieved the minimum levels at stage Ⅳ and stage Ⅴ ovaries,but with a significant increase at stage Ⅵ ovary.It was significantly positive correlated with brain IGF-Ⅰ mRNA levels and serum IGF-Ⅰ levels,but significantly negative correlated with serum E2 and serum T levels during ovarian development.Brain IGF-Ⅰ mRNA levels significantly increased since stage lⅡ ovary and peaked at stage Ⅳ ovary,and showed a significant negative relationship with serum IGF-Ⅰ levels.Ovary IGF-Ⅰ mRNA levels significantly increased at stage Ⅱ ovary and peaked at stage Ⅳ ovary,then significantly declined at stage Ⅴ ovary until stage Ⅵ ovary.It was significantly correlated with serum E2 levels but negatively correlated with serum IGF-Ⅰ levels.Serum IGF-Ⅰ levels showed similar trend with liver IGF-Ⅰ mRNA levels,which significantly decreased at stage Ⅳ ovary,but then significantly ascended to peak at stage Ⅵ ovary.These results revealed that GH and IGF-Ⅰ synergistically or antagonistically play physiological role in ovarian development of C.semilaevis in endocrine or paracrine ways,and their regulation functions are related with synthesis/secretion during ovary development regulation.The present results could provide a new clue for better understanding the possible mechanism for reproductive regulation of C.semilaevis.