Plasma atrial natriuretic peptide degraded by >50% in 1 month even at -80 degrees C, remaining stable for 1 month only when stored at -196 degrees C in liquid nitrogen.
What are the optimal storage conditions to prevent degradation of human plasma atrial natriuretic peptide (ANP)?
Plasma ANP is highly unstable under standard storage conditions (-80°C), requiring storage at -196°C (liquid nitrogen) to maintain stability for 1 month, raising concerns about the validity of prior literature.
BACKGROUND: Atrial natriuretic peptide (ANP) is a hormonal regulator of cardiovascular fluid volume. More than 1,000 scientific articles were written about ANP between 1987 and 1991. Because some articles hinted at problems with storing ANP, this study examined the effect of numerous techniques for storing and processing human ANP samples. METHODS AND RESULTS: Samples were obtained repeatedly from three patients, treated, and stored under a variety of conditions. Experiment 1 evaluated the effects of different preservatives at 35, 21, 14, 10, and 7 days before assay. Experiment 2 evaluated nonspecific binding of ANP to different storage tubes during 28 days of storage. Experiment 3 evaluated the effect of storage at -20 degrees C, -80 degrees C, and -196 degrees C for 1 month. ANP was very unstable, degrading as much as 30% after 3 days of storage and by more than 50% in 1 month even when stored at -80 degrees C. Only storage at -196 degrees C (in liquid nitrogen) kept ANP stable for 1 month. Extraction and lyophilization of the samples before freezing and assay within 7 days of freezing only partially minimized the amount of degradation. All other processing techniques had little effect on slowing the degradation of ANP. CONCLUSIONS: These findings raise disturbing questions about the interpretation of the substantial literature on ANP.
Nelesen et al. (1992) studied this question. Storage at -196 degrees C (liquid nitrogen) vs. Storage at -20 degrees C and -80 degrees C, various preservatives and tubes was evaluated on ANP stability and degradation. Plasma atrial natriuretic peptide degraded by >50% in 1 month even at -80 degrees C, remaining stable for 1 month only when stored at -196 degrees C in liquid nitrogen.