半胱胺盐酸盐(CSH)对尼罗罗非鱼(Oreochromis niloticus)生长及生长轴相关基因表达的影响

EFFECTS OF CSH ON THE GROWTH AND GENE EXPRESSIONS OF THE GROWTH AXIS IN NILE TILAPIA OREOCHROMIS NILOTICUS

为了分析半胱胺盐酸盐(CSH)对尼罗罗非鱼生长调节的作用,设计了长期和短期2个实验,采用腹腔注射(剂量100μg/g体重)方法,分析CSH对尼罗罗非鱼绝对生长率、特定生长率、肝体系数和肥满度的影响,并应用荧光实时定量PCR方法检测在注射CSH后不同时段(6h,12h,24h,2周)尼罗罗非鱼垂体GH、肝脏GHR和肝脏IGF-I基因的表达变化。结果表明,CSH组尼罗罗非鱼的绝对生长率、特定生长率、肝体系数、肥满度均显著高于对照组(P<0.05);注射CSH后12h、24h垂体GH和肝脏GHRmRNA表达水平均显著升高(P<0.05),2周后恢复到对照组水平;注射CSH后6h肝脏IGF-ImRNA表达水平显著升高(P<0.05),12h恢复到对照组水平,24h和2周表达水平极显著上升(P<0.01)。以上结果提示,CSH可显著上调尼罗罗非鱼生长轴相关基因的表达,从而促进鱼类的生长。

Regulations of the synthesis and secretion of growth hormone （GH） in teleosts are based on the dual control of hypothalamic stimulators, gonadotropin-releasing hormone （GnRH）, dopamine （DA）, growth hormone-releasing hormone （GHRH）, and hypothalamic inhibitors, somatostatin （SS） and norepinephrine （NE）. SS is the main inhibitor of basal and neuroendocrine-stimulated GH release. Cysteamine （CS） is a potent somatostatin depletory, and significantly promotes animal growth. Nile tilapia （Oreochromis niloticus） is a fresh-water fish with sexual dimorphism. The effects of CSH on the growth and expressions of GH, GHR and IGF-I mRNA in Nile tilapia remain unclear. Two experiments, designated as long-period and short-period experiments, were carried out. In the long-period experiment, two hundreds Nile tilapias of similar body weight were randomly assigned into the control group （intraperitoneal injection with phosphate saline ） and the CSH group （intraperitoneal injection with CSH, 100μg/g body weight） and fed under the same conditions for 70 days. The absolute growth rates （AGR）, special growth rates （SGR）, condition factor （CF） and hepatosomatic index （HSI） were obtained by measuring the body length, body weight and hepatic weight at different stages. The AGRw （or AGRL） of CSH-treated male and female were increased by 26.48% and 21.48% （or 10.58% and 28.90%）, respectively, comparing to control group （P〈0.05）. During 0--2, 2--6, and 6--10 weeks, the SGRw （or SGRL） of CSH-treated male was elevated by 25.54%, 1.83%, and 49.94% （or 7.87%, 1.08%, and 25.00%）, respectively, comparing to the control group （P〈0.05）; similarly, the SGRw （or SGRL） of CSH-treated female was increased by 25.10%, 10.82%, and 1.77% （or 8.06%, 33.33%, and 23.08%）, respectively （P〈0.05）. Furthermore, the CF and HIS of the CSH group were also significantly higher than those of the control group （P〈0.05）. In the short-period experiment, one hundred and twenty Nile tilapias of similar body weight were randomly assigned into the control group （intraperitoneal injection with phosphate saline） and the CSH group （intraperitoneal injection with CSH, 1001ag/g body weigth） and sampled at 6, 12, 24h, and 2 week. Real time quantitative PCR was applied to detect the expressions of GH in pituitary and GHR and IGF-I in liver at different stages after injection. The expressions of GH in pituitary and GHR in liver were elevated at 12h and 24h （P〈0.05）, but showed no changes at 6h and 2 week. The expression of IGF-I in liver was elevated at 6h （P〈0.05） and returned to the level of control group at 12h, but was elevated significantly at 24h and 2 week （P〈0.01）. The results indicated that CSH could increase the mRNA expressions of GH in pituitary and GHR and IGF-I in liver, and significantly promote growth of Nile tilapia.