Cartwright James, Green Richard M
Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire, RG42 6EY, UK.
Vet Clin Pathol. 2010 Sep;39(3):354-7. doi: 10.1111/j.1939-165X.2010.00231.x.
The enzyme 4-hydroxyphenylpyruvate dioxygenase (HPPD) is key in tyrosine catabolism. Inhibition of HPPD results in tyrosinemia and increased urinary excretion of 3 phenylketones: 4-hydroxyphenylpyruvate (HPPA), 4-hydroxyphenyllactate (HPLA), and 4-hydroxyphenylacetate (HPAA). A previous study involving administration of a novel HPPD inhibitor to dogs resulted in detection of ketonuria in treated animals using urine dipsticks read by reflectance photometry. Dipstick-positive results were suspected to be false because high concentrations of urinary phenylketones have been reported to react with ketone test fields of urine dipsticks, but visual confirmation was not performed.
The purpose of this study was to determine which of the 4- hydroxyphenolic acids produced by HPPD inhibition react with ketone test fields of 3 commercially available urine dipsticks.
Canine urine samples were prepared with HPPA, HPLA, HPAA, and lithium acetoacetate (positive control) at 6 concentrations. Unmodified urine samples were used as negative controls. All samples were tested for ketones using Combur 10 Test M dipsticks read by a Miditron dipstick analyzer. Urinalysis was also performed by visually inspecting ketone test fields on the Combur 10 Test M, Multistix 10 SG, and Aution 10 EA dipsticks.
Urine samples containing HPPA were positive for ketones with Combur 10 Test M dipsticks read by the Miditron analyzer and produced a red–brown color change in ketone test fields of all 3 dipsticks. Urine samples containing HPLA and HPAA were negative by all methods.
The phenylketone HPPA reacts with ketone test fields of 3 commercially available urine dipsticks, producing a red–brown color change that may be misinterpreted as positive for ketones by reflectance photometry.
4-羟基苯丙酮酸双加氧酶（HPPD）是酪氨酸分解代谢中的关键酶。抑制HPPD会导致酪氨酸血症，并增加3种苯酮在尿液中的排泄：4-羟基苯丙酮酸（HPPA）、4-羟基苯乳酸（HPLA）和4-羟基苯乙酸（HPAA）。先前一项对犬类施用新型HPPD抑制剂的研究，通过反射光度法读取尿试纸条检测到受试动物出现酮尿症。尿试纸条呈阳性结果被怀疑是假阳性，因为据报道高浓度的尿中苯酮会与尿试纸条的酮类检测区发生反应，但未进行目视确认。
本研究的目的是确定HPPD抑制产生的4种羟基酚酸中，哪一种会与3种市售尿试纸条的酮类检测区发生反应。
用6种浓度的HPPA、HPLA、HPAA和乙酰乙酸锂（阳性对照）制备犬尿液样本。未处理的尿液样本用作阴性对照。所有样本均使用由Miditron试纸条分析仪读取的Combur 10 Test M试纸条检测酮类。还通过目视检查Combur 10 Test M、Multistix 10 SG和Aution 10 EA试纸条上的酮类检测区进行尿液分析。
用Miditron分析仪读取Combur 10 Test M试纸条时，含HPPA的尿液样本酮类呈阳性，并且在所有3种试纸条的酮类检测区均产生红棕色颜色变化。含HPLA和HPAA的尿液样本通过所有方法检测均为阴性。
苯酮HPPA与3种市售尿试纸条的酮类检测区发生反应，产生红棕色颜色变化，通过反射光度法可能会被误判为酮类阳性。
