Progesterone metabolism during storage of blood samples from Gyr cattle: Effects of anticoagulant, time and temperature of incubation

Abstract

Ten Gyr cows with a functional corpus luteum were used to evaluate the effects of time and temperature of incubation of blood samples on progesterone (P4) concentrations detected in plasma or serum. From each cow, a blood sample was collected into a flask containing no anticoagulant, another into an heparinized flask and a third into a flask containing sodium fluoride. The blood from each flask was divided into 46 aliquots. One of them was centrifuged within 5 min of collection. The remaining 45 aliquots were divided into three groups and kept at three different temperatures: 4°C, 17°C, or 37°C. For each anticoagulant, aliquots from every cow and incubation temperature were centrifuged every 30 min for 6 h, and then at 8, 12 and 24 h. Plasma or serum were separated immediately after centrifugation and were kept frozen at −20°C until assayed for progesterone. The mean initial concentration of P4 in serum (8.3 ng/ml) significantly diminished (P<0.05) to 6.7 ng/ml after 5 h of incubation at 4°C, 3 h at 17°C, or 2 h at 37°C. In plasma from heparinized blood the initial concentration (7.8 ng/ml) declined significantly after 6 h of incubation at 4°C, 2 h at 17°C, or 1 h at 37°C. Sodium fluoride used as anticoagulant prevented the degradation of P4 since the initial concentration of P4 (6.7 ng/ml) never declined during incubation at either 4°C or 37°C; the only significant reduction occurred after 24 h of incubation at 17°C.