Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 2/23/2007
Publication Date: 7/8/2007
Citation: Klotz, J.L., Kirch, B.H., Aiken, G.E., Arrington, B.C., Bush, L.P., Strickland, J.R. 2007. Ergocryptine and Ergonovine Induced Contractile Responses in Fescue Naive Bovine Lateral Saphenous Veins. J. Anim. Sci. Vol. 85, Suppl. 1/J. Dairy Scit. Vol. 90, SUppl. 1/Poult. Sci. Vol. 86 Suppl 1. pg 13. Interpretive Summary:
Technical Abstract: Alpha-Ergocryptine (ERP; ergopeptine alkaloid) and ergonovine (ERN; ergoline alkaloid) are two alkaloids found in endophyte-infected tall fescue. 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 ERP and ERN 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=6; 280 '26 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 ERP or ERN (1x10-11 to 1x10-4 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 (1x10-4 M). Exposure of vein segments to increasing concentrations of ERP and ERN did not result in appreciable contractile response until 1x10-7 M. The two alkaloids did not differ in potency, but did in contractile intensity, with the 1x10-4 M response to ERN reaching a maximum of 68.5 '7.7% and 42.9 '7.9% for ERP. The contractile response to increasing concentrations of these alkaloids 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 greatest contractile intensity. This experiment demonstrates two additional causative agents that may be involved in the loss of vascular plasticity concomitant with consumption of toxic endophyte-infected tall fescue.