Allegri Graziella, Costa Carlo V L, Ragazzi Eugenio, Bertazzo Antonella, Biasiolo Monica
Department of Pharmaceutical Sciences, University of Padova, Via Marzolo 5, I-35131 Padova, Italy.
Adv Exp Med Biol. 2003;527:465-71. doi: 10.1007/978-1-4615-0135-0_54.
In some animals, the administration of repeated doses of tryptophan can cause death. It has been reported that guinea pig does not survive repeated doses of tryptophan, due to the absence of the hormonal induction mechanism of liver tryptophan 2,3-dioxygenase (TDO). Therefore, it was of interest to investigate if guinea pig is an animal model suitable for studying tryptophan metabolism. The activities of the enzymes of the kynurenine pathway were determined. Liver TDO was present only as a holoenzyme; kynurenine 3-monooxygenase showed similar, but very high, activity in both liver and kidney. Liver and kidney kynureninase values were also similar, whereas kynurenine-oxoglutarate transaminase activity was higher in kidney than in liver. 3-Hydroxyanthranilate 3,4-dioxygenase gave similar, but very high, values in both liver and kidney, whereas aminocarboxymuconate-semialdehyde decarboxylase activity was double in kidney with respect to liver, but much lower than that of 3-hydroxyanthranilate 3,4-dioxygenase. Total and free tryptophan concentrations in serum were also determined. The free fraction was about 10% of total tryptophan.
在一些动物中，重复给予色氨酸会导致死亡。据报道，由于缺乏肝脏色氨酸2,3-双加氧酶（TDO）的激素诱导机制，豚鼠无法在重复给予色氨酸后存活。因此，研究豚鼠是否是适合研究色氨酸代谢的动物模型很有意义。测定了犬尿氨酸途径中各种酶的活性。肝脏TDO仅以全酶形式存在；犬尿氨酸3-单加氧酶在肝脏和肾脏中的活性相似，但非常高。肝脏和肾脏中的犬尿氨酸酶值也相似，而犬尿氨酸-酮戊二酸转氨酶活性在肾脏中高于肝脏。3-羟基邻氨基苯甲酸3,4-双加氧酶在肝脏和肾脏中的值相似，但非常高，而氨基羧基粘康酸半醛脱羧酶活性在肾脏中是肝脏的两倍，但远低于3-羟基邻氨基苯甲酸3,4-双加氧酶。还测定了血清中总色氨酸和游离色氨酸的浓度。游离部分约占总色氨酸的10%。
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