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ARS Home » Midwest Area » Lexington, Kentucky » Forage-animal Production Research » Research » Publications at this Location » Publication #242101
Title: Contractile response of fescue-naïve bovine lateral saphenous veins to increasing concentrations of tall fescue alkaloids

Author
item Klotz, James
item KIRCH, BRETT - Colorado State University
item Aiken, Glen
item BUSH, LOWELL - University Of Kentucky
item Strickland, James

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2009
Publication Date: 9/25/2009
Citation: Klotz, J.L., Kirch, B.H., Aiken, G.E., Bush, L.P., Strickland, J.R. 2009. Contractile Response of Fescue-Naïve Bovine Lateral Saphenous Veins to Increasing Concentrations of Tall Fescue Alkaloids. J Anim Sci. 88:408-415.

Interpretive Summary: Various alkaloids found in endophyte-infected tall fescue have been shown to elicit different effects in the grazing animal. As part of an ongoing characterization of vascular response generated by different alkaloids, the objective this study was to examine the vasoconstrictive potentials of ergonovine (a simple lysergic acid derivative) and a-ergocryptine, ergocristine, and ergocornine (all ergopeptine alkaloids) using bovine lateral saphenous veins (cranial branch) biopsied from fescue-naïve cattle. Findings in this study indicate that ergopeptines structurally different only at a single position of the peptide moiety do not exhibit differing contractile responses when considering contractile intensity. This difference may alter the potency when considering ergocornine was less potent than ergocryptine or ergocristine. These alkaloids may need to be considered when evaluating causative agents vasoconstriction associated with tall fescue-induced toxicosis.

Technical Abstract: Various alkaloids found in endophyte-infected tall fescue have been shown to elicit different effects in the grazing animal. As part of an ongoing characterization of vascular response generated by different alkaloids, the objective this study was to examine the vasoconstrictive potentials of ergonovine (a simple lysergic acid derivative) and a-ergocryptine, ergocristine, and ergocornine (all ergopeptine alkaloids) using bovine lateral saphenous veins (cranial branch) biopsied from fescue-naïve cattle. Segments (2-3 cm) of vein were surgically biopsied from healthy cross-bred yearling cattle (n = 18; 274 ±8 kg). Veins were trimmed of excess fat and connective tissue, sliced into 2-3 mm sections and suspended in a myograph chamber containing 5 mL of oxygenated Krebs-Henseleit buffer (95% O2/5% CO2; pH = 7.4; 37'C). Tissue was allowed to equilibrate at 1 g of tension for 90 min prior to initiation of treatment additions. Increasing doses of each alkaloid (1×10-10 to 1×10-4 M) were administered every 15 min following buffer replacement. Data were normalized as a percent of contractile response induced by a reference dose of norepinephrine (1×10-4 M). Exposure of vein segments to increasing concentrations of ergocryptine, ergocristine, and ergonovine did not result in a contractile response until 1×10-7 M, and ergocornine was even less potent (P < 0.05). Ergonovine had a greater maximal contractile intensity than ergocristine and ergocryptine (P < 0.05), with the 1×10-4 M responses of ergonovine, ergocristine, ergocryptine, and ergocornine reaching maximums of 68.5 '4.1, 45.5 ±4.5, 42.9 '4.1%, and 57.2 ±9.9% of the norepinephrine maximum, respectively. The contractile response to increasing concentrations of ergonovine vs. ergocryptine, ergocristine, and ergocornine were opposite from previous evaluations of ergoline (e.g. lysergic acid) and ergopeptine (e.g. ergovaline) alkaloids using this bioassay, where the ergopeptine generated the greater contractile intensity. These data indicate that ergopeptines structurally different only at a single position of the peptide moiety do not exhibit differing contractile responses when considering contractile intensity. This difference may alter the potency when considering ergocornine was less potent than ergocryptine or ergocristine. These alkaloids may need to be considered when evaluating causative agents vasoconstriction associated with tall fescue-induced toxicosis.