鲫鱼、草鱼离体肠道利用酪氨酸和脯氨酸合成蛋白质与脂肪的研究

THE STUDIES ON PROTEIN AND FAT SYNTHESIZED FROM L-TYROSINE AND L-PROLINE BY THE INTESTINES OF C.AURATUS AND GRASS CARP IN VITRO

该试验采用同位素示踪技术和肠道离体灌流模型分别测定了鲫鱼、草鱼肠粘膜中结合在蛋白质与脂类中的酪氨酸、脯氨酸的量。结果表明:用于合成脂肪的酪氨酸和脯氨酸比例在鲫鱼和草鱼均极显著高于用于合成蛋白质的相应氨基酸比例(p<0.01),但草鱼用于合成脂肪的酪氨酸和脯氨酸比例均显著高于鲫鱼(p<0.05)。在酪氨酸各浓度组中鲫鱼肠道利用其合成蛋白质与脂肪的绝对量几乎都高于草鱼,但从相对量上看,鲫鱼利用酪氨酸合成蛋白质和脂肪的能力显著不如草鱼(p<0.05)。对于每一浓度组的脯氨酸,鲫鱼肠道利用其合成蛋白质的绝对量和相对量均显著高于草鱼(p<0.05),说明鲫鱼利用脯氨酸合成蛋白质的能力显著高于草鱼;但从相对量来看,除了1.0mmol/L试验组外,鲫鱼利用脯氨酸合成脂肪的能力显著低于草鱼(p<0.05)。

Recent researches discover that the mucous membrane of gut renews frequently and it is the main tissue which consumes energy in vivo. The energy used by the mucosa of terrestrial animal gut accounts for 20% of the total energy in the body and amino acids such as Glutamine rather than Glucose are the leading energy material utilized by intestines. Therefore,amino acids absorbed from daily ration （or from blood） are partly used for oxidative decomposition or protein synthesis by intestines itself. Thus,the utilization of essential amino acids from daily ration by the mucosa of gut maybe influence the full development of nutrition value of daily ration. For the moment,a few articles which state the ab- sorption of amino acids by intestines of aquatic animals have been delivered, but the studies in which the absorption protein synthesis and liquid synthesis of amino acids by intestines are measured at the same time in identical conditions are few reported. The studies were conducted to determine protein and fat synthesized from L-Tyrosine and L-Proline by the intestines of C. auratus and Grass carp in vitro by using L-[4,5-3H] Tyrosine and L-[2,3,4,5-3H] Proline as tracers and adopting the in-vitro perfusion technique, and then approach general laws about both amino acids absorption and utilization by aquatic animals intestines and also offer necessary theoretical basis for formulating ideal feedstuff of amino acids balance. In this experlment,the concentrations of L-Tyr are designed 0. 5mmol/L, 1.5mmol/L and 2.5mmol/L and the concentrations of L-Pro are 1.0 mmol/L,5.0mmol/L and 10.0mmol/L respectively, according to the respective solvency of the two different amino acids. Experimental amino acids are infused into the whole in-vitro gut of fishes, meantime, the flux was controlled at the invariable speed of 2.0mL/min by pump. At the 40min of perfusion, transmural amino acids across gut wall, free animo acids retained in gut wall,protein-synthesized amino acids and fat-synthesized amino acids are meas-ured accurately. The results indicated that most amino acids retained in intestines compound fat and the others partly existed freely in guts, partly used for protein synthesis and so on. The percentage of amino acids used for fat synthesis was extremely markedly higher than that of amino acids used for protein synthesis in both C. auratus and Grass carp（p 〈0.01 ） ,and the percentage of amino acids for fat synthesis in Grass carp was markedly higher than that in C. auratus（p 〈0.05）. Experimental results showed that the absolute amount of L-Tyr of every concentration team used for protein synthesis in C. auratus was on the whole higher than that in corresponding Grass carp,and so was especially the absolute amount for fat synthesis,but the ability of C. auratus utilizing L-Tyr for protein synthesis and fat synthesis was markedly lower than that of Grass carp（p 〈 0.05）. To every Pro concentration team, the absolute amount and relative percentage of proteinbound L-Pro in C. auratus were all markedly higher than those in corresponding Grass carp（p 〈 0.05 ） , which indicated that the ability of C. auratus using L-Pro for protein synthesis was markedly higher than that of Grass carp（p 〈 0.05） ;but the ability of C. auratus using L-Pro for fat synthesis was markedly lower than that of corresponding Grass carp except for 1.0mmol/L experimental team （p 〈 0.05 ）.