The Effects of Prostaglandin E 2 Treatment on the Secretory Function of Mare Corpus Luteum Depends on the Site of Application: An in vivo Study.

We examined the effect of prostaglandin (PG) E ₂ on the secretory function of equine corpus luteum (CL), according to the application site: intra-CL injection vs. an intrauterine (intra-U) administration. Moreover, the effect of intra-CL injection vs. intra-U administration of both luteotropic factors: PGE ₂ and human chorionic gonadotropin (hCG) as a positive control, on CL function was additionally compared. Mares were assigned to the groups ( n = 6 per group): (1) an intra-CL saline injection (control); (2) an intra-CL injection of PGE ₂ (5 mg/ml); (3) an intra-CL injection of hCG (1,500 IU/ml); (4) an intra-U saline administration (control); (5) an intra-U administration of PGE ₂ (5 mg/5 ml); (6) an intra-U administration of hCG (1,500 IU/5 ml). Progesterone (P ₄ ) and PGE ₂ concentrations were measured in blood plasma samples collected at -2, -1, and 0 (pre-treatment), and at 1, 2, 3, 4, 6, 8, 10, 12, and 24 h after treatments. Moreover, effects of different doses of PGE ₂ application on the concentration of total PGF _2α (PGF _2α and its main metabolite 13,14-dihydro-15-keto-prostaglandin F _2α - PGFM) was determined. The time point of PGE ₂ , hCG, or saline administration was defined as hour "0" of the experiment. An intra-CL injection of PGE ₂ increased P ₄ and PGE ₂ concentrations between 3 and 4 h or at 3 and 12 h, respectively ( p < 0.05). While intra-U administration of PGE ₂ elevated P ₄ concentrations between 8 and 24 h, PGE ₂ was upregulated at 1 h and between 3 and 4 h ( p < 0.05). An intra-CL injection of hCG increased P ₄ concentrations at 1, 6, and 12 h ( p < 0.05), while its intra-U administration enhanced P ₄ and PGE ₂ concentrations between 1 and 12 h or at 3 h and between 6 and 10 h, respectively ( p < 0.05). An application of PGE ₂ , dependently on the dose, supports equine CL function, regardless of the application site, consequently leading to differences in both P ₄ and PGE ₂ concentrations in blood plasma.
Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2022 Piotrowska-Tomala, Jonczyk, Szóstek-Mioduchowska, Żebrowska, Ferreira-Dias and Skarzynski.)