犬猫血浆中游离及总胱氨酸的测定。

Determination of free and total cyst(e)ine in plasma of dogs and cats.

作者信息

Tôrres Cristina L, Miller Joshua W, Rogers Quinton R

机构信息

Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA.

出版信息

Vet Clin Pathol. 2004;33(4):228-33. doi: 10.1111/j.1939-165x.2004.tb00378.x.

DOI:10.1111/j.1939-165x.2004.tb00378.x

PMID:15570560

Abstract

BACKGROUND

In human blood, the amino acid cysteine forms disulfide bonds with itself and with other sulfhydryl compounds in their free form and with sulfhydryls in protein. Protein-bound cysteine is lost when plasma proteins are removed before amino acid analysis.

OBJECTIVE

The purpose of this study was to assess the time course and extent of cyst(e)ine (cysteine + half-cystine) loss in dog and cat plasma.

METHODS

An equal volume of 6% sulfosalicylic acid was added to plasma aliquots at 0, 2, 4, 10, 16, 24, 36, 48, 60, and 72 hours after separation of blood cells. Tris-2-carboxyethyl-phosphine hydrochloride (TCEP - HCl), a reducing agent, was used to regenerate total plasma cyst(e)ine after 3 months of sample storage (-20 degrees C).

RESULTS

Initial free cyst(e)ine concentrations (mean +/- SEM) were higher in canine plasma (77 +/- 4 micromol/L) than in feline plasma (37 +/- 3 micromol/L). Free plasma cyst(e)ine concentrations in dogs and cats decreased after first-order kinetics, with a half-life of 23 and 69 hours, respectively. Total plasma cysteine after TCEP - HCl treatment was similar for dogs (290 micromol/L) and cats (296 micromol/L), but the percentage of free cysteine was higher (P = .02) in dogs (27%) than in cats (13%). Over half of the cyst(e)ine, homocysteine, cysteinylglycine, and glutathione were bound in vivo to plasma proteins.

CONCLUSION

These results emphasize the importance of removing plasma proteins within 1 hour after blood collection for reliable assay of free plasma cyst(e)ine.

摘要

背景

在人体血液中，氨基酸半胱氨酸会自身形成二硫键，也会与其他游离形式的巯基化合物以及蛋白质中的巯基形成二硫键。在进行氨基酸分析之前去除血浆蛋白时，与蛋白质结合的半胱氨酸会丢失。

目的

本研究旨在评估犬猫血浆中胱（基）氨酸（半胱氨酸+半胱氨酸）丢失的时间进程和程度。

方法

血细胞分离后0、2、4、10、16、24、36、48、60和72小时，向血浆样本中加入等体积的6%磺基水杨酸。使用还原剂盐酸三（2-羧乙基）膦（TCEP - HCl）在样本储存3个月（-20℃）后再生总血浆胱（基）氨酸。

结果

犬血浆中初始游离胱（基）氨酸浓度（均值±标准误）（77±4 μmol/L）高于猫血浆（37±3 μmol/L）。犬猫血浆中游离胱（基）氨酸浓度呈一级动力学下降，半衰期分别为23小时和69小时。TCEP - HCl处理后的犬总血浆半胱氨酸（290 μmol/L）和猫（296 μmol/L）相似，但犬游离半胱氨酸的百分比（27%）高于猫（13%）（P = 0.02）。超过一半的胱（基）氨酸、同型半胱氨酸、半胱氨酰甘氨酸和谷胱甘肽在体内与血浆蛋白结合。