Location: Forage-animal Production ResearchTitle: Endophyte-infected tall fescue seed extract induces constriction of bovine vasculature) Author
Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract only
Publication Acceptance Date: 3/8/2011
Publication Date: 7/11/2011
Citation: Foote, A.P., Harmon, D.L., Brown, K.R., Strickland, J.R., Mcleod, K.R., Bush, L.P., Klotz, J.L. 2011. Endophyte-infected tall fescue seed extract induces constriction of bovine vasculature. Joint Meeting of the ADSA, AMSA, ASAS and PSA. 89(E-Suppl. 1):49-50. Interpretive Summary:
Technical Abstract: Ergovaline (ERV) has been extensively used to study vasoactive effects of endophyte (Neotyphodium coenophialum) infected tall fescue (Lolium arundinaceum). However preliminary in vitro tests show that an extract of toxic tall fescue seed (E+EXT) is more potent than ERV alone indicating other compounds contribute to vasoconstriction. Thus, experiments were conducted to determine if vasoactivity of an E+EXT is different than a mixture of ergot alkaloids (ALK) of equal concentration and to determine if an endophyte-free extract (E-EXT) is vasoactive. Segments of lateral saphenous vein and right ruminal artery and vein were collected from steers (n=6) shortly after slaughter. Vessels were cleaned of excess connective tissue and fat and sliced into segments that were suspended in a multi-myograph chamber with 5 mL of continually oxygenated Krebs-Henseleit buffer, equilibrated for 90 min, and exposed to a reference compound, 120 mM KCl for ruminal vessels and 0.1 mM norepinephrine for saphenous vein. Increasing concentrations of each treatment (E+EXT, E-EXT, ALK, and ERV) were added to the respective chamber every 15 min following buffer replacement. Data were normalized as a % of maximal contractile response of the reference compound and analyzed as a CRD. For saphenous vein, ALK and E+EXT induced similar responses (P=0.1847 for 10-6 M; P=0.2835 for 10-7 M) that were greater than 10-6 M ERV (P=0.0028 and P=0.088 respectively) and 10-7 M ERV (P<0.0001 and P=0.0019 respectively). ERV displayed a greater EC50 than ALK and E+EXT (P<0.0014) in saphenous vein indicating ERV alone was less potent. For ruminal artery, ALK and E+EXT induced similar responses (P=0.31 for 10-6; P=0.056 for 10-7) that were greater than ERV at 10-6 M (P=0.001 and P<0.0001 respectively) and 10-7 M (P=0.04 and P=0.0001 respectively). For ruminal vein, ALK and E+EXT induced similar responses (P=0.13) but E+EXT didn’t differ from ERV (P=0.61). E-EXT didn’t induce a contractile response in any vessel tested (P>0.1). Although low in concentration, non-ergovaline alkaloids in E+EXT contribute to the observed contractile response and should be considered when studying fescue toxicosis.