Changes in porcine,ovine, bovine and equine blood progesterone concentrations between collection and centrifugation

The aim of this study was to determine if different methods of handling porcine, ovine, bovine and equine blood between collection and centrifugation influence measurable progesterone levels. A 2 × 2 × 5 factorial experiment was conducted for each species with heparin (with or without), temperature of incubation (4 and 22°C) and time of incubation (0, 6, 12, 24 and 48 h) as the main effects. Following centrifugation, plasma and serum samples were stored at ?20°C until progesterone concentrations were determined by radioimmunoassay. Method of handling porcine and equine blood between collection and centrifugation did not affect the levels of progesterone. However, heparinized blood held at 4°C resulted in the most consistent levels of progesterone over time. Progesterone levels were fairly consistent across time in the ovine blood by all methods of handling except heparinized blood incubated at 22°C. By 24 h after collection, plasma progesterone concentrations decreased by 50% for the ovine blood incubated at 22°C with heparin. Decreases were detected by all the methods of handling the bovine blood between collection and centrifugation. The rate of decline, however, was considerably faster for blood held at 22°C than blood held at 4°C. At 12–48 h after collection, the concentrations of progesterone averaged only 5% of the time 0 sample for blood incubated at 22°C. In contrast, at least 30% of the progesterone values in the time 0 sample were detected between 12 and 48 h of incubation for the blood held at 4°C.