Time and temperature effects, between collection and centrifugation, on nellore cows serum and plasma progesterone concentration

Abstract

The objective of this study was to determine the effects of time and temperature, between collection and centrifugation, on the progesterone levels in serum and plasma samples. Seventy-two blood samples (with and without heparin) from three nelore pregnant cows were collected and incubated at 4 or 28°C during 0, 1, 2, 4, 8 and 24 hours. Immediately after each incubation period, the samples were centrifuged and the serum and plasma stored at -20^oC until analyses. The evaluation of the progesterone concentration in the samples was done by radioimmunoassay. A significative reduction (over 60%; P < 0.05) in relation to the initial values, in the serum levels of progesterone occurred after four hours in the samples stored at 4°C and after two hours in the samples at 28°C. The reductions in the levels of progesterone in plasma was over 70% (P < 0.01) for the samples stored at 4 or 28°C. Thus, for the determination of progesterone levels, the blood samples must be centrifuged as quickly as possible after collection, and maintened at 4°C during this period.