中文摘要：

目的筛选并鉴定对大鼠乳腺发育和泌乳调控起关键作用的微RNAs（mi RNAs）。方法以U6为内参基因,运用实时荧光定量PCR,比较mi R-142-3p、mi R-145-3p在泌乳21 d大鼠乳腺、肝、心、脾、肺、肾、卵巢、子宫各器官的组织样品表达量的差异及不同泌乳阶段（1、7、21 d）乳腺组织mi R-142-3p、mi R-145-3p的表达规律。结果mi R-142-3p在泌乳21 d各组织的表达存在差异,乳腺中的表达量显著高于心、脾、肺、肾、卵巢和子宫,仅次于肝中的表达量（P〈0.05）。mi R-145-3p在乳腺中的表达量显著高于肝、脾和肾,而在心、肺、卵巢和子宫中差异无统计学意义（P〉0.05）。乳腺组织在泌乳1、7、21 d比较,mi R-142-3p的相对表达量持续下调,而mi R-145-3p的相对表达量先下调后上调。结论 mi R-142-3p和mi R-145-3p在大鼠各组织及不同生理时期存在表达差异;mi R-142-3p可通过调节靶基因催乳素受体（Prlr）来调控乳腺的发育和泌乳的形成,mi R-145-3p可能具有与mi R-145、mi R-145-5p相似的功能。

英文摘要：

Objective To screen and identify the key mi RNAs during mammary gland development and milk secretionof rats. Methods Gene U6 was taken as interior label gene by real time-PCR to compare the differences of expression levelsof mi R-142-3p and mi R-145-3p in the mammary gland, liver, heart, spleen, lung, kidney, ovary and uterus after 21 postpartum.Moreover, the expressions of mi R-142-3p and mi R-145-3p in different stages（1, 7 and 21 d） of lactation were summarized.Results There was significant difference in mi R-142-3p in lactation 21 d between different tissues. The expression of mi R-142-3p was significantly higher in mammary gland than that in heart, spleen, lung, kidney, ovary and uterus tissues, which wassecond only to the expression in liver（P 0.05）. The expression of mi R-145-3p was significantly higher in mammary glandthan that in liver, spleen and kidney. There was no significant difference in the expression of mi R-145-3p between heart, lung,ovary and uterus（P 0.05）. Furthermore, the relative expression level of mi R-142-3p was continuing downward continued todecline in breast at different stages of lactation, while the relative expression level of mi R-145-3p was up-regulated after down-regulating. Conclusion mi R-142-3p and mi R-145-3p are differentially expressed in different tissues and physiological periodsin rats. In addition, mi R-142-3p can regulate the growth of mammary gland and the formation of lactation by targeting prolactinreceptor（Prlr）, mi R-145-3p may have the same function with mi R-145 and mi R-145-5p.