β-酪啡肽7促大鼠胃内胃泌素的表达

Effect of β-casomorphin 7 on expression of gastrin mRNA in rat stomach

本实验研究了β-酪啡肽7(β-casomorphin7,βCM7)在成年大鼠胃内的吸收及对胃黏膜中胃泌素(gas-trin)表达的影响。实验包括3个部分:1)将成年大鼠胃贲门和幽门结扎,并分别对胃伴行血管和网膜进行结扎和不结扎处理,采用反相HPLC法发现,胃注射βCM7在两种不同处理中相同时间点的βCM7浓度无统计学差异;2)体外酶解实验表明,βCM7能抗成年大鼠胃黏膜酶水解并以完整的分子形式存在;3)将成年雄性SD大鼠设为对照组和3个试验组,分别灌喂1ml生理盐水、7·5×10-9mol/L纳洛酮(Naloxone,NaL)、7·5×10-9mol/LβCM7和7·5×10-9mol/LNaL+7·5×10-9mol/LβCM7。饲养周期为30d。半定量RT-PCR法观察了大鼠胃黏膜中胃泌素和生长抑素(Somatostatin,SS)mRNA表达的变化。结果显示:βCM7组能显著刺激胃黏膜中胃泌素基因的表达(n=8,P<0·05),且该效应不能被纳洛酮逆转;NaL组大鼠胃黏膜中胃泌素基因的表达极显著低于对照和各试验组(n=8,P<0·01);仅βCM7组能显著抑制胃黏膜中SS基因的表达(n=8,P<0·05)。上述结果表明:βCM7不能被成年大鼠胃黏膜吸收且能以完整的肽结构存在;βCM7可能通过抑制SSmR-NA表达来促进胃黏膜中胃泌素的表达。

The aim of the present study was to evaluate the characteristic absorption of native bovine β-CM7 in stomach of adult rats, and the local effect of β-CM7 on expression of gastrin from gastric mucosa. 1 ） To characterize the absorption of the β-CM7, the different surgical procedures were designed in experimental and control group respectively. Both gastric cardia and pylorus were ligated, and then the blood vessel in the omentum accompanying with the greater and lesser of stomach was tied and cut off just in control group to block absorption. A similar descended tendency of the dynamic variety of infusing β-CM7 （0.1 mg/L, 1 ml） concentration in digesta of stomach was observed between experimental and control （block absorption） groups by RP-HPLC. 2） To characterize the metabolic processes of the β-CM7 in vitro, the peptide was digested with rat gastric mucosa homogenate, and then was analyzed by HPLC. The result implied that β-CM7 could exit as intact molecular in stomach. 3） SD rats were randomly assigned to four treatment groups respectively, basal diet ＋ physiological saline, basal diet ＋ naloxone （7.5× 10^9 mol/L）, basal diet ＋ β-CM7 （7.5 × 10^-9 mol/L）, basal diet ＋ β-CM7 ＋ naloxone （containing equal mol of drug 7.5 × 10^-9 mol/L）, bovine β-CM7 （7.5 × 10^-9 mol/L） after luminal administration for 30 days contributed to gastric mucosa gastrin mRNA expression （132.8 % of control, P 〈 0.05）. But the effect on gastrin mRNA expression was not blocked by naloxone simultaneity applied with β-CM7. This peptide also significantly inhibited the expression of somatostatin mRNA （28.64 % of control, P 〈 0.05）. In conclusion, the present data demonstrated that natural bovine β-CM7 existed in stomach of adult rats as intact molecule. The effect of β-CM7 on regulation of expression of gastrin mRNA might not be related to its opioid activity. One could speculated that β- CMs might have a local effect on regulating the expression of gastrin mRNA by direct or indirect affection on expression of somatostatin mRNA .