ADRENOMEDULLIN SIGNALLING IN BOVINE CORPUS LUTEUM DURING OESTROUS CYCLE, GRAVIDITY AND INDUCED LUTEOLYSIS

Investigations on nonclassic regulators of angiogenesis could open new perspectives in understanding angiogenesis under physiological and pathological conditions. A proangiogenic effect has been demonstrated for adrenomedullin (AM), it´s co-factor activitymodifying protein 2 (RAMP-2) and the calcitonin receptor-like receptor (CALCLR). This signalling pathway is besides associated with lymphangiogenesis, that (in a physiologically way) is still only poorly understood in ovary and its structures. The aim of this study was therefore to evaluate mRNA expression of AM, RAMP-2 and CALCLR in bovine corpora lutea (CL) during different physiological stages. Experiment 1: CL were assigned days 1-2, 3-4, 5-7, 8-12, 13-16, 18 (after regression) of oestrous cycle and of gravidity (month 3, 3- 5, 6-7 and 8). Experiment 2: Induced luteolysis. Cows on days 8-12 were injected with a PGF2α analogue and CL were collected by transvaginal ovariectomy before and 0.5, 2, 4, 12, 24, 48 and 64 h after PGF2α injection. Tissue levels of mRNA were characterized by qPCR. All 3 factors were clearly expressed. AM and CALCRL showed significant changes in both experiments, RAMP-2 during induced luteolysis. For AM highest levels could be observed in the beginning and the end of the luteal phase, CALCRL remained at around the same levels. Both factors showed their most expression at the end of pregnancy. During induced luteolysis all factors started to decline not until structural luteolysis. In conclusion, our results could lead to the assumption that factors investigated may be involved in mechanisms regulating CL formation, function and regression – and a special impact in the final month of pregnancy