肽结合与游离氨基酸比例对离体乳腺组织酪蛋白合成的影响

Effects of the Proportion of Peptide Binding and Free Amino Acids on Casein Synthesis in the Mammary Gland Explants

本研究以离体培养的泌乳奶牛乳腺组织为材料,分别以Met-Met二肽或Arg-His-Ile三肽等量替代培养基中相应的FAA,替代比例为0%(对照)、5%、10%、15%、20%、40%、60%、80%和100%(三肽的替代比例以His的量为标准),检测乳腺组织酪蛋白-αs1(CSN1S1)、PepTⅡ、氨肽酶(ANPEP)的mRNA表达量及酪蛋白-β(β-casein)、PepTⅡ、氨肽酶(ANPEP)蛋白表达量。结果表明,Met-Met二肽替代FAA显著提高了CSN1S1的mRNA表达量、β-casein的蛋白表达量,以及PepTⅡ的mRNA和蛋白表达量(P<0.05),但对ANPEP的mRNA表达量没有显著影响(P>0.05);Arg-His-Ile三肽替代FAA对CSN1S1的mRNA和蛋白表达量影响不显著;但可以显著提高PepTⅡ的mRNA和蛋白表达量(P<0.05)。本研究的结果表明,以一定比例的小肽(如Met-Met)替代游离氨基酸可以被乳腺组织吸收利用并可促进酪蛋白合成,而且通过PepTⅡ载体转运进入乳腺上皮细胞是被吸收利用的主要途径。

The lactating bovine mammary tissue in vitro in the treatment medium was cultured in this study,FAA were substituted with different proportion of 0%(as control),5 %,10%,15%, 20%,40%,60%,80%and 100%of Met-Met or Arg-His-Ile(tripeptide Arg-His-Ile was substituted with His as of proportions).The mRNA expression levels of casein-αS1(CSN1S1),PepTⅡ, ammonia peptide enzyme(ANPEP)and the protein expression levels of casein-β(β-casein)PepT Ⅱand ANPEP were detected.The results show that:replacing FAA with Met-Met significantly increased the mRNA expression of CSN1S1,the protein expression ofβ-casein,and also both mRNA and protein expressions of PepTⅡ(P<0.05).However,the mRNA expression of ANPEP had no significant change(P>0.05).While,Arg-His-Ile substitution had no significant effect on either mRNA expression of CSN1S1or protein expression,but both mRNA and protein expression of PepTⅡwere significantly increased.This study support the hypothesis that mammary tissue can make use of Met-Met as amino acid source at certain percentage and enhance the synthesis of casein.Moreover,peptide transporterⅡ(PepTⅡ)may be the main mechanism allowing thesmall peptides be transported into the mammary epithelial cells.