Journal List > Korean J Lab Med > v.29(2) > 1011523

Kim, Kwon, and Lee: The Comparison of Parathyroid Hormone Degradation Effect by Various Protease Inhibitors in Blood Specimen

Abstract

Background

The objective of this study was to evaluate the role of proteases on the degradation of parathyroid hormone (PTH) in blood samples.

Methods

Protease inhibitors with specificity against serine proteases (aprotinin), cysteine proteases (E-64), serine and cysteine proteases (leupeptin), metalloproteases (EDTA), or a protease inhibitor cocktail with a broad spectrum of inhibitory activity were added to blood samples. After storage at room temperature (0-48 hr), PTH levels were measured.

Results

PTH levels in samples with the protease inhibitor cocktail did not change significantly after 48 hr of storage at room temperature, but the average PTH levels decreased by 40.7% and 20.1%, in samples stored at room temperature and stored at 4°C without protease inhibitors, respectively. PTH levels in samples with leupeptin were stable for up to 24 hr. After 48 hr, the mean PTH levels decreased by 17.1%, 16.0%, 26.2%, and 32.1%, with 500 KIU/mL aprotinin, 100 μmol/L leupeptin, 10 μmol/L E-64, and 10 μmol/L EDTA, respectively, in the samples stored at room temperature.

Conclusions

The decrease in PTH levels in blood samples seemed to be due to the degradation of PTH by proteases. Various proteases, including especially serine proteases, would act together to degrade PTH in blood specimen. The PTH degradation may be inhibited in blood specimen with protease inhibitor cocktail.

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Fig. 1.
Time-dependent changes of the PTH levels in samples with different kinds of protease inhibitors. Data points are the mean ±SD (error bars) of PTH levels. Six groups of samples were stored at room temperature and the other group was stored at 4°C. Abbreviation: PTH, parathyroid hormone.
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Table 1.
Changes of PTH levels in blood specimen according to different storage conditions
Storage condition PTH levels (pg/mL) P
Zero time After 12 hr After 24 hr After 48 hr
Storage at room temperature          
 Without protease inhibitors 35.4±13.1 28.1±8.4 23.8±.4 21.0±6.2 0.005
 With protease inhibitors          
  Inhibitor cocktail 34.7±12.4 33.6±12.7 33.14±11.9 33.3±11.5 0.139
  Aprotinin, 500 KIU/mL 35.6±12.6 33.5±11.8 31.8±12.7 29.5±11.0 0.005
  Leupeptin, 100 μmol/L 45.0±9.0 43.6±15.9 41.9±15.7 37.8±14.2 0.028
  E-64, 10 μmol/L 34.3±12.2 30.6±10.9 28.7±11.3 25.3±9.9 0.005
  EDTA, 10 μmol/L 34.9±13.5 30.1±9.8 26.4±9.5 23.7±8.3 0.008
Storage at 4°C          
 Without protease inhibitors 35.9±14.2 33.6±13.7 30.6±12.4 28.7±11.1 0.009

, PTH levels are given as mean ±SD;

, Comparison between zero time PTH levels and those after 48 hr was performed using the Wilcoxon signed-rank test.

Abbreviations: PTH, parathyroid hormone; EDTA, ethylene diamine tetra-acetic acid

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