AUTHOR=Jonczyk Agnieszka W. , Piotrowska-Tomala Katarzyna K. , Skarzynski Dariusz J. 

TITLE=Comparison of Intra-CL Injection and Peripheral Application of Prostaglandin F2α Analog on Luteal Blood Flow and Secretory Function of the Bovine Corpus Luteum

JOURNAL=Frontiers in Veterinary Science

VOLUME=8

YEAR=2022

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2021.811809

DOI=10.3389/fvets.2021.811809

ISSN=2297-1769

ABSTRACT=<p>We investigated the effects of different doses of dinoprost injected directly into the bovine corpus luteum (CL) on (i) concentrations of progesterone (P<sub>4</sub>) and oxytocin (OT) in peripheral blood and (ii) mRNA levels of steroidogenic acute regulatory protein (STAR), cytochrome P450 family 11 subfamily A member 1 (P450scc), hydroxy-delta-5-steroid dehydrogenase, 3 β- and steroid delta-isomerase 1 (HSD3B), and receptor-interacting protein kinases 1 and 3 (RIPK1, RIPK3) in CL tissue. Moreover, we examined the effects of dinoprost, injected intra-CL or administered intramuscularly (IM), on CL secretory function and on indicators of CL vascular network status: luteal tissue area (LTA), CL blood flow (CLBF), and the CLBF:LTA ratio (Adj. CLBF), in cows at the early and mid-luteal phases. In the Experiment 1, cows (day 10 of the cycle) were allocated to (i) an intra-CL injection of saline (control; <italic>n</italic> = 3); (ii) an intra-CL injection of dinoprost (1.25 mg; 2.5 mg, or 5 mg; <italic>n</italic> = 3 for each dose); (iii) an IM administration of saline (control; <italic>n</italic> = 3); or (iv) an IM administration of dinoprost (25 mg; positive control; <italic>n</italic> = 3). Concentrations of OT and P<sub>4</sub> were measured in plasma samples. The mRNA expression of steroidogenesis- or necroptosis-related factors was determined in CL tissue 4 h after treatments. In Experiment 2, cows on day 4 (<italic>n</italic> = 12) or day 10 (<italic>n</italic> = 12) were allocated to (i) an intra-CL injection of dinoprost (2.5 mg/0.5 ml; <italic>n</italic> = 6), or (ii) IM administration of dinoprost (25 mg/5 ml; <italic>n</italic> = 6). Concentrations of P<sub>4</sub> were measured in plasma samples. Luteal tissue area, CLBF, and Adj. CLBF were assessed based on color Doppler ultrasonography. An intra-CL injection of dinoprost increased OT and decreased P<sub>4</sub> levels in the jugular vein (JV) in a dose-dependent manner in cows at the mid-luteal phase. Increased CLBF and Adj. CLBF, accompanied by reduced P<sub>4</sub> levels, were observed 2 h after intra-CL dinoprost injection in middle-stage CL. Decreased <italic>STAR</italic> and increased <italic>RIPK1</italic> and <italic>RIPK3</italic> mRNA levels confirmed that 2.5 mg dinoprost injected directly into CL is the minimum dose that induces luteolytic cascade. Injection of dinoprost directly into the CL (at a dosage lower than recommended for peripheral application) results in a pattern similar to IM dinoprost administration.</p>