Submitted to: International Symposium on Fungal Endophytes of Grasses
Publication Type: Abstract Only
Publication Acceptance Date: April 19, 2010
Publication Date: June 28, 2010
Citation: Foote, A.P., Klotz, J.L., Bush, L.P., Strickland, J.R., Harmon, D.L. 2010. An Extract of Endophyte Infected Tall Fescue Seed Induces Vasoconstriction of Bovine Foregut Vasculature. International Symposium on Fungal Endophytes of Grasses. pp 33-34. Technical Abstract: An ethanol extract of tall fescue seed was produced to further understand the interactions of toxic compounds that cause fescue toxicosis. We hypothesized that the combination of alkaloids present in the extract would have a greater vasoconstrictive response than individual alkaloids. The objective of this study was to compare the vasoconstrictive response of right ruminal artery and vein to ergovaline (ERV), lysergic acid (LSA), and an extract (EXT) adjusted to a measured ERV concentration. Segments of right ruminal artery and vein were collected from the ventral coronary groove of predominately Angus heifers (n=10) shortly after slaughter and placed in a modified Krebs-Henseleit buffer. Vessels were cleaned of connective tissue and fat, sliced into 2-3 mm segments and suspended in a multi-myograph chamber with 5 mL of continuously oxygenated Krebs-Henseleit buffer (95 %O2/5% CO2; pH 7.4; 37°C). Arteries and veins were equilibrated to 1.0 g and 0.5 g respectively for 90 min followed by addition of 120 mM KCl. Increasing concentrations (10-11M to 10-6M) of each compound were added to the respective chamber every 15 min following buffer replacement. Data were normalized as a fraction of the contractile response induced by KCl and were analyzed as a completely randomized design using PROC MIXED of SAS. Contractile response was greater in the artery than vein for ERV and EXT (P<0.05) but not LSA. Increasing concentration of LSA did not affect contractile response in either vessel (P>0.05). The maximum contractile response observed was higher for EXT than ERV for the artery (P<0.05). The greatest ruminal vein response to EXT was seen at 10-7M which was greater than ERV at equal concentration (P<0.05) and was similar to 10-6M ERV. These data indicate that the combinatorial effect of alkaloids is greater than individual alkaloids and that ERV is not solely responsible for fescue toxicosis symptoms.