Interactions of circulating estradiol and progesterone on changes in endometrial area and pituitary responsiveness to GnRH

Author(s):Show less -

Motta, Jessica C. L. ^{[1, 2]} ; Madureira, Guilherme ^{[1, 2]} ; Silva, Lucas O. ^[1] ; Alves, Rodrigo L. O. R. ^[1] ; Silvestri, Mayara ^[1] ; Drum, Jessica N. ^{[1, 2]} ; Consentini, Carlos E. C. ^[1] ; Prata, Alexandre B. ^{[1, 2]} ; Pohler, Ky G. ^[3] ; Wiltbank, Milo C. ^[2] ; Sartori, Roberto ^[1]

Affiliation

^[1] Univ Sao Paulo, Luiz de Queiroz Coll Agr ESALQ, Dept Anim Sci, Av Padua Dias 11, BR-13418900 Piracicaba, SP - Brazil

^[2] Univ Wisconsin Madison, Dept Anim & Dairy Sci, Madison, WI - USA

^[3] Texas A&M Univ, Dept Anim Sci, College Stn, TX 77843 - USA

• Document type: Journal article
• Source: BIOLOGY OF REPRODUCTION; v. 103, n. 3, p. 643-653, SEP 2020.
• Web of Science Citations: 0

Abstract

Changes in circulating progesterone (P4) and estradiol (E2) during proestrus produce dynamic changes in endometrial function and pituitary release of gonadotropins. Independent and combined effects of P4 and E2 on endometrium and pituitary were evaluated. In a preliminary study, an exogenous hormone model of proestrus was created by removal of corpus luteum and follicles >= 5 mm followed by gradual removal of intravaginal P4 implants during 18 h and treatment with increasing doses of estradiol benzoate during 48 h to mimic proestrus using high E2 (n = 9) or low E2 (n = 9). Decreased P4, increased E2, and increased endometrial area (EA) simulated proestrus in high-E2 cows and this was used subsequently. The main experiment used a 2 x 2 factorial design with: high E2 and low P4 (n = 11); high E2 and high P4 (n = 11); low E2 and high P4 (n = 11); low E2 and low P4 (n = 10). At 48 h, gonadotropin-releasing hormone (GnRH)-induced luteinizing hormone (LH) and follicle stimulating hormone (FSH) release was determined. Variables were analyzed using PROCMIXED of Statistical Analysis System. The EA increased dramatically during 48 h only in highE2 and low-P4 cows. For FSH, high-E2 cows had greater area under the curve (AUC) and FSH peak after GnRH than low E2, with mild negative effects of high P4. For LH, concentration at peak and AUC were 2-fold greater in high E2 compared to low-E2 groups, with low P4 also 2-fold greater than high-P4 groups. Thus, maximal changes in uterus and pituitary during proestrus depend on both low P4 and high E2, but different physiologic responses are regulated differently by E2 and P4. Changes in endometrium depend on low P4 and high E2, whereas GnRH-induced FSH secretion primarily depends on high E2, and GnRH-induced LH secretion is independently increased by high E2 or reduced by high P4. (AU)

• FAPESP's process: 18/03798-7 - Studies on ovarian and uterine physiology and improvement of Assisted Reproduction Technologies to increase reproductive efficiency in cattle
• Grantee: Roberto Sartori Filho
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 17/16701-9 - Influence of circulating concentrations of estradiol and progesterone on endometrial thickness and LH and FSH concentrations after GnRH treatment
• Grantee: Jéssica Cristina Lemos Motta
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 18/09266-7 - Comparing and improving techniques for progesterone and estradiol assays using bovine plasma samples from previous experiments that evaluated the influence of these steroids on endometrial thickness
• Grantee: Jéssica Cristina Lemos Motta
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree