Rendle D I, Litchfield E, Gough S, Cowling A, Hughes K J
School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, New South Wales, Australia.
Equine Vet J. 2015 Sep;47(5):587-91. doi: 10.1111/evj.12319. Epub 2014 Oct 7.
Previous reports suggest that adrenocorticotrophic hormone (ACTH) degrades rapidly, limiting its use as a diagnostic test.
This study quantified effects of processing delays on ACTH concentrations and investigated the addition of N-phenylmaleimide (maleimide), a protease inhibitor, as a means of reducing ACTH degradation.
Experimental study.
Venous blood was collected from 8 healthy horses and 8 horses with pituitary pars intermedia dysfunction (PPID) with a range of ACTH concentrations. Baseline ACTH concentrations were established immediately using a chemiluminescent assay. Plasma samples were then: 1) centrifuged immediately, 2) centrifuged immediately with the addition of maleimide, or 3) allowed to separate by gravity followed by the addition of maleimide, before all samples were stored at 22°C and analysed at 4, 8, 24 and 48 h post collection. A linear mixed effects model and Bland-Altman analyses were performed. Significance was set at P < 0.05.
No significant effect of plasma treatment (P = 0.1) on change in ACTH concentration was identified. However, significant effects of horse health status (P < 0.001) and time (P < 0.001) on change in ACTH concentration were identified. No significant interactions were found. Significant decreases in ACTH concentration occurred in horses with PPID between 4 and 8 h after blood collection. In non-PPID horses, the decrease in ACTH concentration over time was not significant. Agreement with baseline values decreased over time and was greater for non-PPID horses than for PPID horses.
Clinically useful results are still obtained if ACTH concentration is measured up to 48 h after sample collection. Allowing samples to separate by gravity rather than centrifugation did not have a significant effect on ACTH concentration, and the addition of maleimide was of no benefit.
既往报告提示促肾上腺皮质激素（ACTH）降解迅速，限制了其作为诊断试验的应用。
本研究对处理延迟对ACTH浓度的影响进行量化，并研究添加蛋白酶抑制剂N-苯基马来酰亚胺（马来酰亚胺）作为减少ACTH降解的一种方法。
实验性研究。
采集8匹健康马和8匹患有垂体中间叶功能障碍（PPID）且ACTH浓度各异的马的静脉血。立即采用化学发光法测定基线ACTH浓度。然后将血浆样本：1）立即离心，2）添加马来酰亚胺后立即离心，或3）让其自然分层后添加马来酰亚胺，之后所有样本均在22°C保存，并在采集后4、8、24和48小时进行分析。进行线性混合效应模型和Bland-Altman分析。显著性设定为P < 0.05。
未发现血浆处理对ACTH浓度变化有显著影响（P = 0.1）。然而，发现马的健康状况（P < 0.001）和时间（P < 0.001）对ACTH浓度变化有显著影响。未发现显著的交互作用。PPID马在采血后4至8小时ACTH浓度显著下降。在非PPID马中，ACTH浓度随时间的下降不显著。与基线值的一致性随时间降低，且非PPID马比PPID马更大。
如果在样本采集后48小时内测量ACTH浓度，仍可获得临床有用的结果。让样本自然分层而非离心对ACTH浓度没有显著影响，添加马来酰亚胺也无益处。
