The Comparison of Parathyroid Hormone Degradation Effect by Various Protease Inhibitors in Blood Specimen

Abstract

Parathyroid hormone (PTH) is released from the parathyroid glands and regulates bone and mineral metabolism. It is a single-chain 84-amino acid polypeptide with a molecular weight of 9,425 Daltons. It is synthesized and secreted by the parathyroid glands, and rapidly cleared from plasma (half-life <5 min). PTH is metabolized to C-terminal fragments by the liver and kidneys, and cleared by the kidney, either as intact PTH or as C-terminal fragments [1]. 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 μ mol/L leupeptin, 10 μ mol/L E-64, and 10 μ mol/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. (Korean J Lab Med 2009;29:104-9)

The effect of different protease inhibitors on stability of parathyroid hormone, insulin, and prolactin levels under different lag times and storage conditions until analysis

“…Consistent with previous reports, we found that PTH levels in samples without protease inhibitors to be significantly decreased starting from 24 hours, which exceeded DBL at 48 and 72 hours when stored at RT . Additionally, we have shown that storing the samples at 4°C, even without protease inhibitors preserves PTH levels.…”

“…T A B L E 6 The medians (25-75 percentile), percent change values, and statistical analyses for insulin, PTH, and prolactin measurements in K 2 -EDTA tubes which were stored at 4°C or RT, until analyzed at 6, 24, 48, and 72 hours in 10 healthy adults stored at RT. 18,19 Additionally, we have shown that storing the samples at 4°C, even without protease inhibitors preserves PTH levels.…”

CASE REPORT: Metastatic pancreatic polypeptide-secreting islet cell tumor in a dog

“…Peptide hormones tend to degrade with time if not treated with protease inhibitors, such as apotrinin. 14 The prevalence of pure PP-secreting islet cell tumors is very low in dogs. There is only 1 study reporting a tumor exhibiting positive immunolabeling exclusively for PP.…”