Repeated induction of abortion in bitches and the effect on plasma concentrations of relaxin, progesterone and estradiol-17β

The aim of the present study was to investigate the effects of two medications on two subsequent abortions and plasma hormone concentrations of dogs. For this purpose, two groups of bitches (n = 5 each), received the antiprogesterone aglepristone (Alizine®) at 10 mg/kg body weight on two subsequent days around day 30 after mating. In group II, the antiprolactin cabergoline (Galastop®) was additionally administered po at 5 μg/kg body weight until the start of abortion. The plasma concentrations of relaxin, progesterone (P4) and estradiol-17β (E2) were measured before, during and after each abortion. During the next cycle after the abortion, the same bitches were mated again and in pregnant animals, induction of abortion was performed as before. During the third cycle, pregnant bitches were allowed to whelp. Termination of first pregnancy occurred significantly earlier after the combined treatment (6.8 versus 10.6 days, p < 0.05). In both groups and during both abortions, relaxin varied between individuals; however, there was a continuous decrease after the abortions and no significant differences between groups (p > 0.05). In one bitch with high relaxin concentrations before treatment (11.6 ng/ml), a cystic endometrial hyperplasia was diagnosed. In the aglepristone only group, P4 concentrations increased significantly after the first application (p < 0.05), then decreased continuously until day 45 after the beginning of abortion. In the combined group, there was a continuous decrease until day 45 (p > 0.05). At this time, P4 concentrations between 0.47 and 84.9 nmol/l were measured in both groups. The level of E2 over time was not influenced by any medication. We therefore note that the two medications mainly influenced plasma concentrations of P4 in different ways, probably due to specific treatment-hormone interactions. However, all measurements fell within the range considered normal.