Acute Changes in the Concentrations of Prostaglandin F2α (PGF) and Cortisol in Uterine and Ovarian Venous Blood During PGF‐induced Luteolysis in Cows

Abstract

Prostaglandin F2α (PGF) is considered to be the main luteolysin in cattle. We have previously demonstrated that cortisol (Cr) suppresses PGF production in non-pregnant bovine endometrium. This study was carried out to test whether exogenous PGF increases ovarian and/or uterine PGF production and to determine the temporal relationship between PGF and Cr in ovarian and uterine circulations during PGF-induced luteolysis in cows. Catheters were inserted into the ovarian vein (OV), uterine vein (UV) and jugular vein (JV) of 10 cows on Day 9 of the oestrous cycle (Ovulation = Day 0) for frequent blood collection. On Day 10, the cows were divided randomly into two groups and treated with a luteolytic dose of a PGF analogue (cloprostenol) or saline solution. Blood samples were collected at -0.25, 0, 0.25, 0.5, 1 and 2 h and then at 2-h intervals until 12 h after treatment (0 h). The basal concentrations of PGF and Cr in OV and UV plasma were not significantly different. Injection of a PGF analogue induced more than twofold increases in the levels of PGF between 0.25 and 1 h in UV plasma, but not in OV plasma. PGF increased (p < 0.05) the concentrations of Cr in OV, UV and JV plasma between 0.5 and 1 h. The Cr levels in OV, UV and JV plasma were similar. The PGF levels in UV plasma decreased after Cr reached its highest levels. The overall results suggest that the uterus rather than the ovary increases PGF production in response to PGF injection. Based on the temporal changes of PGF and Cr in the ovarian and uterine circulations, Cr may act to reduce uterine PGF production in non-pregnant cows in vivo.

Conversion of Cortisone to Cortisol and Prostaglandin F2α Production by the Reproductive Tract of Cows at the Late Luteal Stage In Vivo

“…Recent in vivo studies (Shrestha et al. 2010; Duong et al. 2011b) have shown that Cr plays a role in regulating PGF secretion in the bovine uterus during PGF‐induced luteolysis.…”

“…2010). Furthermore, a concomitant elevation of uterine PGF and Cr concentrations was observed after an analogue of PGF injection and then concentration of PGF decreased after Cr reached its highest levels (Duong et al. 2011b).…”

“…At surgery, 18‐gauge catheters were inserted into the UV 3–5 cm from uterine horn before joining the utero‐ovarian vein ipsilateral to the functional CL (Woclawek‐Potocka et al. 2010; Duong et al. 2011b), the VCC and AA and fixed to the surrounding connective tissue (Skarzynski et al.…”

“…2009). We recently showed that injection of PGF in vivo induced acute increases in the levels of circulating Cr (Duong et al. 2011b).…”

Effects of Cortisol on Pregnancy Rate and Corpus Luteum Function in Heifers: An <i>In Vivo</i> Study

“…Thus, for the initiation of bovine luteal regression, the pulsatile character of PGF 2α is much more important and plays a mandatory role rather than its absolute levels [56,57]. Furthermore, cortisol has been suggested to act in reducing the high levels of uterine PGF and to be one of the factors responsible for the generation of PGF 2α pulses in vivo in cattle [58]. Cortisol is well-known as a local regulator/modulator of PG secretion [8].…”