Department of Biochemistry and Molecular Biology, Mississippi State University, Box 9650, 39762, MS.
Fish Physiol Biochem. 1996 Apr;15(2):131-42. doi: 10.1007/BF01875592.
Three separate experiments were conducted to investigate the utilization of dietary free amino acids by white sturgeon,Acipenser transmontanus. In the first experiment, sturgeon were fed for 8 weeks with isoenergetic and isonitrogenous diets containing either intact protein, an amino acid mixture, or a neutralized amino acid mixture of similar composition. Sturgeon fed the two amino acid diets grew significantly (p<0.05) less, mainly because of reduced feed intake. In the second experiment, postprandial changes in plasma free amino acids of sturgeon force-fed the above diets were monitored at 2, 4, 6, 8, 12, and 24 h Total plasma amino acids in sturgeon force-fed the intact protein diet showed a gradual increase and reached peak levels at 8 h. In contrast, plasma amino acids of fish force-fed the amino acid diets showed a rapid increase and reached maximal levels at 2 h. In the third experiment, free amino acid diets showed a urine of sturgeon force-fed the three diets was monitored at 4, 8, 12, 16, 20, and 24 h. In all dietary groups, peak excretion of indispensable amino acids was detected at 8 h after feeding but with significantly higher levels from fish force-fed the amino acid diets. Sturgeon force-fed the neutralized amino acid diet excreted 35% less amino acids compared to fish force-fed the non-neutralized diet. Sturgeon force-fed the intact protein diet excreted significantly higher amounts of ammonia. Under amino acid feeding conditions, sturgeon excreted more amino acids in its urine, but the urinary excretion of amino acids was not a major route in dealing with the rapid absorption of dietary free amino acids.
三项独立实验研究了白鲟（Acipenser transmontanus）对饲料游离氨基酸的利用。在第一项实验中，白鲟连续 8 周摄食等能量和等氮的饲料，其中包含完整蛋白、氨基酸混合物或组成相似的中性氨基酸混合物。摄食两种氨基酸饲料的白鲟生长显著减少（p<0.05），主要是由于采食量降低。在第二项实验中，摄食上述饲料的白鲟被强制灌食后，监测其血浆游离氨基酸的餐后变化，在 2、4、6、8、12 和 24 小时进行检测。摄食完整蛋白饲料的白鲟的总血浆氨基酸逐渐增加，在 8 小时达到峰值。相比之下，摄食氨基酸饲料的鱼的血浆氨基酸在 2 小时达到最大水平。在第三项实验中，监测摄食三种饲料的白鲟的尿液在 4、8、12、16、20 和 24 小时的变化。在所有饮食组中，摄食后 8 小时检测到必需氨基酸的排泄峰值，但摄食氨基酸饲料的鱼的排泄水平显著更高。与摄食未中和氨基酸饲料的鱼相比，摄食中性氨基酸饲料的白鲟排泄的氨基酸减少 35%。摄食完整蛋白饲料的白鲟排泄的氨显著更高。在氨基酸摄食条件下，白鲟在尿液中排泄更多的氨基酸，但尿液中氨基酸的排泄不是处理膳食游离氨基酸快速吸收的主要途径。
