Endocrine and cellular characteristics of corpora lutea from cows with a delayed post-ovulatory progesterone rise

Robinson, R.S.; Hammond, A.J.; Nicklin, L.T.; Schams, D.; Mann, G.E.; Hunter, M.G.

doi:10.1016/j.domaniend.2005.10.003

« Previous Next »Domestic Animal Endocrinology
Volume 31, Issue 2 , Pages 154-172, August 2006

Endocrine and cellular characteristics of corpora lutea from cows with a delayed post-ovulatory progesterone rise

R.S. Robinson
- Division of Animal Physiology, University of Nottingham, Sutton Bonington Campus, Loughborough, Leics LE12 5RD, UK
- Corresponding author. Tel.: +44 115 9516342; fax: +44 115 9516302.
A.J. Hammond
- Division of Animal Physiology, University of Nottingham, Sutton Bonington Campus, Loughborough, Leics LE12 5RD, UK
L.T. Nicklin
- Division of Animal Physiology, University of Nottingham, Sutton Bonington Campus, Loughborough, Leics LE12 5RD, UK
D. Schams
- Department of Physiology, Technical University Munich-Weihenstephan, Weihenstephaner Berg 3, D-85350 Freising, Germany
G.E. Mann
- Division of Animal Physiology, University of Nottingham, Sutton Bonington Campus, Loughborough, Leics LE12 5RD, UK
M.G. Hunter
- Division of Animal Physiology, University of Nottingham, Sutton Bonington Campus, Loughborough, Leics LE12 5RD, UK

Received 11 July 2005; received in revised form 26 September 2005; accepted 5 October 2005. published online 14 November 2005.

Abstract

The timing of the post-ovulatory progesterone rise is critical to the embryonic development and survival. The aim of this study was to determine the underlying causes of delayed post-ovulatory progesterone rises. Two groups of non-lactating dairy cows with early (n=11) or late (n=9) post-ovulatory progesterone rises were created by inducing luteolysis in the presence of either a large (>10mm) or small (<10mm) follicle, respectively. LH pulses were measured on days 4 (all cows) and 7 (n=7, early; n=5, late) (day 1=ovulation). The cows were slaughtered on day 5 (n=4 each group) or 8 (n=7, early; n=5, late). Immunohistochemical analysis for endothelial cells (von Willebrand Factor, VWF), steroidogenic cells (3β-HSD) and proliferation marker (Ki67) were performed. The basal progesterone production and LH responsiveness (0.001–100ng/ml) of dispersed luteal cells was investigated. The luteal concentrations of FGF-2 and VEGF were measured by ELISA and RIA, respectively. There were no differences in LH pulse characteristics, area of VWF staining, proliferation index, steroidogenic cell characteristics, basal or LH-stimulated progesterone production by luteal cells between cows with an early or late progesterone rise (P>0.10). However, the area of VWF staining increased from days 5 to 8, while the proliferation index decreased (P<0.05). Furthermore, the luteal cells were more responsive to LH on day 8 (P<0.01). Luteal concentrations of FGF-2 were higher on day 5 (P=0.05), while VEGF was greater on day 8 (P<0.01). In conclusion, we have clearly shown that LH support, degree of vascularization or luteal cell steroidogenic capacity were not the major factors responsible for inadequate secretion of progesterone by the developing bovine CL.