Studies on the Luteal Function in the Late Pregnant Cow

Corpora lutea (CL) from cows at 270 (5) or 250 (5) days of gestation were incubated with LH or cAMP. CL of cows at 250 days had increased progesterone accumulation in response to LH and cAMP while the group at 270 days did not respond to LH. Higher plasma concentrations of estrogens were found in the group at 270 days pregnant however progesterone and PGFM were not different among groups. In a second experiment, 8 cows at 245 days of gestation received intravenous infusion of estrone or vehicle during 5 days. CL were removed at 120 hours after the beginning of the infusion for in vitro incubations with LH and cAMP. Estrone infusion caused an increase in the concentrations of unconjugated estrone, and unconjugated and conjugated estradiol-17B in plasma but no change occurred in conjugated estrone, progesterone, cortisol, PGF2a, PGFM and LH concentrations. In vitro luteal function was not affected by estrone infusion. However, maximal luteal response was correlated with pre-infusion concentrations of conjugated estrogens suggesting a negative association between endogenous conjugated estrone and luteal function. The third experiment was undertaken after the lutectomy following estrone or vehicle infusion in experiment 2. PGF2a was estimated in the uterine vein, PGFM in the carotid artery and progesterone in both sampling sites. Higher concentrations of progesterone as well as a slower rate of progesterone decline were observed in the uterine vein than in the carotid artery. These results indicated that the placenta is an active source of progesterone at 250 days of gestation. The high plasma concentrations of estrogens induced by estrone did not affect placental production of progesterone. No changes over time were observed in PGF2a and PGFM concentrations after lutectomy in both groups. However, plasma concentrations of PGF2a were higher in the estrone-infused group than in the control group.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Veterinary Medical Science

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Pimentel, Claudio Alves

• Biology, Veterinary Science

Identifier

(UMI)AAI8209617

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71291