Abstract
ABSTRACTIn this study, endometrial samples were collected in 14 Nelore cows on days zero (ovulation), five, nine, thirteen and nineteen of the estrous cycle (biopsy group), and in 15 females these collections weren't performed (control group). Biopsies were done on the uterine horn endometrium contralateral to the ovary with corpus luteum. Blood samples were taken at -24, -16, -8, 0 +8, +16 and +24 hours in relation to progesterone drop (<1ng/mL, zero moment) and evaluated for 13, 14-dihydro-15-keto prostaglandin F2-alpha (PGFM) by radioimmunoassay (RIA). Plasma progesterone concentration was determined by RIA every 24 hours. Data were analyzed by ANOVA using the PROC GLM and MIXED of the SAS. The mean value for PGFM during the entire period evaluated was greater in the biopsy group. The mean concentration of PGFM at moment zero was not different between the groups; the mean concentration of PGFM was higher in the biopsy group before and after the drop in progesterone level. The maximum mean concentration observed was not different between the groups; however, the mean minimum concentration was different with high values in the biopsy group. Although the PGFM concentrations were higher in the biopsy group, the biopsy and control groups had similar length of estrous cycle showing that repeated endometrial biopsy on the side contralateral to the ovary with corpus luteum does not affect luteolysis and the length of the estrous cycle.
Highlights
Luteolysis is a physiological event that occurs between days 15 and 19 of the estrous cycle and is essential to determine the end of the luteal phase, growing of an ovulatory follicle and estrus
It was found that the average value for PGFM during the whole period was greater in the biopsy group compared with controls (81.9±10.8 vs 51.1±9.8pg/mL respectively, P
On the day of luteolysis, there was no difference between the biopsy and control groups (18.3±1.0 vs 18.3±0.6pg/mL days respectively, P=0.2) and the estrous cycle length was similar between the groups (23.69±0.49, control group vs 23.64±0.86, biopsy group, P>0.05)
Summary
Luteolysis is a physiological event that occurs between days 15 and 19 of the estrous cycle and is essential to determine the end of the luteal phase, growing of an ovulatory follicle and estrus. The release of endometrial prostaglandin F2-alpha (PGF2 ) occurs in a pulsatile nature and is essential to induce luteolysis and regression of the corpus luteum (CL) (Okuda et al, 2002; Ginther et al, 2009). The release of PGF2α occurs in response to binding of oxytocin to newly developed receptors in the uterine endometrium (Silvia et al, 1991; Mann et al, 1999). The concentration of plasma PGFM is usually used to evaluate the release of endometrial PGF2α secretion, once it has a longer half-life in peripheral circulation (Kindahl et al, 1976; Granström and Samuelsson, 1978; Kindahl et al, 1984; Mishra et al, 2003)
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