Vasoconstriction induced by ergot alkaloids affects oocyte developmental capacity in pregnant sheep

Authors: ELGARRESTA, C - Clemson University; MUELLER, V - Clemson University; ZARZACA, I - Clemson University; CULLER, H - Clemson University; DUCKETT, SUSAN - Clemson University; Klotz, James; HERSOM, M - Clemson University; CHECURA, CELINA - Clemson University

Submitted to: The International Embryo Technology Society
Publication Type: Abstract Only
Publication Acceptance Date: 7/29/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Consumption of ergot alkaloids from endophyte-infected tall fescue induces vasoconstriction in livestock. Previous work indicates that ergot alkaloid exposure influences vasoactivity through serotonin receptors, by acting as both an agonist and antagonist. The objective of this work was to study the effect of systemic vasoconstriction caused by ergot alkaloids (E+) on the developmental capacity of sheep oocytes, and the potential role of 5-HTP to ameliorate the E+ effects. Suffolk cross ewes were synchronized in 9 weekly groups and bred to a ram fitted with a chest marker. Pregnancy was confirmed around day 45 post-marking, and on day 80 of gestation for each weekly group, 3 ewes carrying twins were randomly assigned to one of three treatments. Ewes were individually fed total mixed ration (TMR) starting on day 80, and treatments started on day 86 as follows: 1: Control (TMR w/no treatment), 2: E+ and 5-HTP (TMR + 1.77 mg/ewe E+ in fescue seed + 2.5 mg/kg BW 5-HTP); and 3: E+ (TMR + E+ in fescue seed). Carotid diameter was obtained by ultrasonography on days 80, 90, 100, and 111. Ovaries were retrieved after euthanasia on day 112 of gestation. Oocytes were collected by aspiration and placed into in vitro maturation (IVM) media (Stroebech IVM for Small Ruminants) at 38.5 ºC, 5% CO2, in high humidity. At 24 hours of IVM, oocytes were vortexed for 1 minute to remove excess cumulus cells and stained with MitoTracker TM Red CMXRos (MTR) to determine mitochondrial membrane potential (3 ewes x 4 reps = 12 ewes) or BioTracker ATP-Red (ATP) for intracellular ATP (3 ewes x 5 reps = 15 ewes). All oocytes were co-stained with Hoechst to determine nuclear maturation. Statistical analysis: Each ewe was considered an experimental unit. A Mixed model of repeated measures was used to analyze carotid diameter over time with main effects of treatment, time, and their interaction, blocked by replicate. Only MII oocytes were used for MTR and ATP statistical analyses. A Mixed model was used for each single endpoint considering the main effect of treatment, blocked by replicate. Significance was set at p<0.05. Carotid diameter showed treatment, time, and interaction effects: both E+ treatments presented a decrease in Carotid diameter by day 90 with an increase to day 100. In treatment 3, carotid diameter on day 111 was still different than the baseline diameter from day 80. Mean oocyte recovery rate was no different among groups, 15.15 ± 1.66 oocytes/ewe. Maturation rates showed a treatment effect, treatment 1 was higher than 2 and tended (p=0.052) to be higher than 3 (31.0 ± 10.2; 11.1 ± 4.4; 14.5 ± 2.9 MII oocytes/stained oocytes for treatments 1, 2, and 3 respectively). Mean relative fluorescence units for MTR and ATP in mature oocytes were not different among treatments. These results indicate that ergot alkaloids induced vasoconstriction and their systemic effects altered the developmental capacity of oocytes to reach nuclear maturation after IVM. The MTR and ATP levels, however, were not affected by the treatments. Further research is needed in this area, considering that only a small number of mature oocytes were included in each bioenergetic analysis.