Abstract
The present study was conducted to find out the changes of progesterone and 20$\alpha$-dihydroprogesterone(20$\alpha$-OHP) levels before and after parturition, 4 pluriparous goats were offered for this experiment. Blood samples were taken from jugular vein on Days, 5, 3, 2 and 1 before parturition, the day of parturition, 1, 3, 5, 7 and 9 after parturition. The blood samples were centraifuged and stored at -2$0^{\circ}C$ until hormone assay. The serum levels of progesterone and 20$\alpha$-OHP were measrued by radioimmunoassay. The changes of serum progesterone level during peripartum period were characterized as a remarkable decrease. The progesterone level was 4.05$\pm$0.52ng/ml on 56 days before parturition and decreased to 2.24$\pm$0.38ng/ml on 1 day before parturition and 0.79$\pm$0.09ng/ml on the day of parturition and the basal level was maintained through 9 days of postpartum period. The serum level of 20$\alpha$-OHP during the peripartum period was 1.25$\pm$0.21ng/ml on 5 days before paturition and increased to 1.32$\pm$0.25 on 3 days and 1.59$\pm$0.24ng/ml on 1 day before parturition, and reached a peak level of 1.78$\pm$0.25ng/ml just prior to parturition and then decreased greatly to 0.31$\pm$0.03ng/ml on 1 day postpartum and the basal level was remained until 9 days postpartum. The high serum level of 20$\alpha$-OHP, which was peak just prior to parturition, was maintained for 2 days following the onset of remarkable decrease in the serum level of progesterone. From the above results, it was concluded that the enzyme 20$\alpha$-hydroxysteroid dehydrogenase (20$\alpha$-HSD) catalyzing the conversion of progesterone to a biologically inactive steroid, 20$\alpha$-OHP was active properly in the luteal cells in Korean native goats.
