Table 2.
Effects of storage in frost-free and nonfrost-free −20°C freezers on biochemical analytes in rat serum
| Mean (n = 10) percentage change from day 0 values |
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| Frost-free freezer |
Nonfrost-free freezer |
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| Analyte | Mean ± SE, day 0 | day 30 | day 90 | day 30 | day 90 |
| Glucose, mg/dL | 153.3 ± 7.0 | 0.6 | 0.7 | 2.5 | 0.3 |
| Blood urea nitrogen, mg/dL | 21.25 ± 0.67 | 0.6 | 3.6 | 4.8 | (1.2) |
| Sodium, mmol/L | 145.8 ± 0.5 | (1.9) | (1.7) | (0.1) | (2.4) |
| Potassium, mmol/L | 5.61 ± 0.07 | 1.1 | 0.4 | 3.1 | (0.1) |
| Chloride, mmol/L | 97.8 ± 0.5 | 2.6 | (1.8) | 5.1 | (3.0) |
| Carbon dioxide, mmol/L | 32.5 ± 0.07 | (12.1)a | (21.5)a | (10.7)a | (18.3)a |
| Amylase, U/L | 1243.0 ± 37.6 | (1.0) | (2.6) | (2.5) | (4.7) |
| Lipase, U/L | 91.5 ± 2.7 | 0.4 | (0.7) | 2.8 | (0.3) |
| Calcium, mg/dL | 11.03 ± 0.08 | 1.2 | (1.7) | 2.8 | (0.8) |
| Phosphorus, mg/dL | 8.64 ± 0.15 | (1.6) | (3.3) | 0.6 | (0.6) |
| Total protein, g/dL | 6.35 ± 0.04 | 2.0 | 4.9 | 3.4 | 4.5 |
| Albumin, g/dL | 3.70 ± 0.04 | 1.7 | 3.6 | 5.5 | 1.1 |
| Aspartate aminotransaminase, U/L | 111.9 ± 3.5 | (1.8) | (2.8) | 1.1 | (4.0) |
| Alanine aminotransaminase, U/L | 92.6 ± 1.6 | (4.8) | (8.8) | (2.0) | (10.3) |
| Lactate dehydrogenase, U/L | 887.0 ± 54.2 | 0.3 | 1.8 | 2.5 | 0.6 |
| Creatine kinase, U/L | 178.1 ± 19.2 | (1.3) | (5.7) | (1.0) | (2.7) |
| Alkaline phosphatase, U/L | 208.9 ± 13.2 | (1.3) | (5.6) | (1.9) | (3.6) |
Values in parentheses indicate decreases from day 0 value.
a
Values are significantly (P < 0.05) different from day 0 value.