Profiles of prostaglandin F2α metabolite in dairy cattle during luteal regression and pregnancy: implications for corpus luteum maintenance†

Abstract

Mechanisms of bovine corpus luteum (CL) maintenance during the second month of pregnancy have not been adequately investigated, despite significant reproductive losses. In the first month, interferon-tau is believed to suppress oxytocin-stimulated prostaglandin F2α (PGF) production, yet there are conflicting reports of circulating PGF metabolite (PGFM). In this study, characterization of PGFM and P4 occurred through continuous bihourly blood sampling in cows undergoing CL regression (day 18–21, n = 5), and during the first (day 18–21, n = 5) and second month (day 47–61; n = 16) of pregnancy. Cattle in the second month were assigned to control (n = 8) or oxytocin treatment (n = 8; three pulses to mimic luteolysis) to evaluate if oxytocin receptors were active. All cows but one (which had elevated PGFM prior to oxytocin treatment) maintained the pregnancy. Basal PGFM concentrations were low (11.6 ± 0.7 pg/mL) in the first month but increased 2.54-fold in the second month. Few (0.26 ± 0.12 pulses/day) PGFM pulses with low peak concentrations (28.8 ± 3.1 pg/mL) were observed during the first month of pregnancy, similar to cows not undergoing regression. However, in the second month, frequency (1.10 ± 0.26 pulses/day) and peak concentration (67.2 ± 5.0 pg/mL) of PGFM pulses increased, displaying similar frequency but lower peak PGFM than seen in regression (1.44 ± 0.14 pulses/day; 134.5 ± 18.9 pg/mL). Oxytocin treatment increased likelihood of PGFM pulses post-treatment and increased peak concentration (89.7 ± 10.1 pg/mL) in cows during the second month. Thus, cows have more PGFM pulses during second than first month of pregnancy, possibly induced by endogenous oxytocin, indicating suppression of PGF production is an important mechanism for CL maintenance during first but not second month of pregnancy.

Downregulated luteolytic pathways in the transcriptome of early pregnancy bovine corpus luteum are mimicked by interferon-tau in vitro

“…On the one hand, pregnant ruminants were reported to have higher concentrations of basal PGF2A than cyclic animals have [ 47 , 48 ]. However, recent publications have suggested that although the numbers of PGF2A pulses per day were significantly higher during luteolysis, compared with pregnant animals, they were similar in the pregnant animals and in those at the late luteal phase [ 40 , 49 ]. Additionally, PGF2A can reach the CL during early pregnancy as shown by Banu and coworkers [ 50 ].…”

Effect of route of administration of dinoprost tromethamine on plasma profiles of 13,14-dihydro-15-keto-prostaglandin F2α and progesterone in lactating Holstein cows

“…All cows were housed in a tiestall barn, fed a standard herd diet, and milked twice daily. On d 6, all cows were fitted with an indwelling jugular catheter as described elsewhere (Mezera et al, 2019) and randomized to 1 of 2 treatments on the morning of d 7 after collection of baseline blood samples 24, 2, 1, and 0 h before treatment. Cows were randomized to the following 2 treatments: (1) 25 mg (2 mL) of dinoprost tromethamine (Lutalyse HighCon; Zoetis) adminis-Effect of route of administration of dinoprost tromethamine on plasma profiles of 13,14-dihydro-15-keto-prostaglandin F 2α and progesterone in lactating Holstein cows M. A. Mezera, 1,2 M. R. Lauber, 1 A. D. Beard, 1,2 E. M. Cabrera, 1 M. C. Wiltbank, 1 and P. M. Fricke 1 * tered intramuscularly in the semitendinosus muscle (IM; n = 6), or (2) administered subcutaneously in the neck contralateral to the jugular catheter (SC; n = 6).…”

“…Concentrations of PGFM were evaluated using an ELISA based on the method reported by Ginther et al (2010) with minor modifications reported by Mezera et al (2019). The intra-and interassay coefficients of variation (CV) were 8 and 14%, respectively, and sensitivity was 5.2 pg/mL.…”

Identification of stable genes in the corpus luteum of lactating Holstein cows in pregnancy and luteolysis: Implications for selection of reverse-transcription quantitative PCR reference genes

“…Multiparous Holstein cows were housed in a tiestall barn, milked twice per day, and fed a standard herd diet. As previously described (Mezera et al, 2019), 32 cows were synchronized, with half bred and half uninseminated. Blood was collected from the jugular vein on d 18 to 21 to analyze circulating progesterone (P4) and PGF 2α metabolite (PGFM) to determine regression status, while biopsies were collected daily from d 18 to 21 with a transvaginal guided ultrasound probe, as described and validated by Tsai et al (2001).…”