Effects of dexamethasone administration to diestrus cows on systemic progesterone, estrogen and uterine cyclooxygenase production.

摘要

Nine cycling crossbred beef cows were maintained on pasture in Louisiana, USA, and given twice daily injections of 8 mg dexamethasone (Azium, treated group) or vehicle (control group) during days 13-22 of a normal oestrous cycle. Uterine endometrialbiopsies were collected on days 16, 19 and 22 of the treatment cycle and blood samples were collected daily on days 13-22. Serum oestradiol concentration in treated cows remained at a stable level (～1picog/ml) from days 15-22 whereas control animals showed 2 peaks of oestradiol concentration on days 15 and 20-22 (P<0.01). There was no difference in serum progesterone concentration between treated and control groups on days 10-17 and 21-22, but on days 18-20 progesterone concentration was lower in treated animals than in controls (P<0.01). The treatment oestrous cycle of treated cows was longer than that of control cows (31 and 24 days, respectively, P<0.01). Cyclooxygenase-1 was sporadically detected in endometrial tissue with no difference betweenthe 2 groups; cyclooxygenase-2 was not detected.