Stability of ovine serum protein fractions under different storage conditions

We evaluated the effect of different storage conditions on the concentration of serum total proteins and their electrophoretic fractions in sheep. Blood samples were collected from 12 female Comisana sheep, and each serum obtained was divided into 4 aliquots. The first aliquot was analyzed immediately after separation (T0); the second was refrigerated at 4°C and analyzed after 24 h (T1), 48 h (T2), and 72 h (T3); the third was stored at -20°C immediately after centrifugation and analyzed after 2 days (T4); and the last aliquot was stored at -20°C after 24-h refrigeration and analyzed after 1 wk (T5). The concentrations of serum total proteins and their electrophoretic fractions (albumin, α-, β1-, β2-, and γ-globulins) was determined. A statistically significant ( p < 0.05) effect of storage conditions on all serum electrophoretic protein fractions and on the albumin-to-globulin (A/G) ratio was found. The values of albumin, α-globulins, and A/G ratio increased at T4 with respect to T0. The levels of α-globulins were higher at T1 than T0; the β1-globulins levels changed at T3, whereas the β2- and γ-globulins values as well as the A/G ratio changed at T2 and T3. At T4, we found an increase in the serum concentrations of albumin, α₁-globulins, and on the A/G ratio, and a decrease of γ fraction. At T5, the concentration of α-globulins was higher than at T0. Hence, we recommend electrophoretic analysis of fresh ovine serum samples or of samples refrigerated for no more than 24 h to obtain accurate data.