title: Assessment of vasoconstrictive potential of D-lysergic acid using an isolated bovine lateral saphenous vein bioassay.
abstract: Vasoconstriction has been associated with several symptoms of fescue toxicosis thought to be alkaloid induced. Lysergic acid, an ergot alkaloid, has been proposed as a toxic component of endophyte-infected tall fescue. The objective of this study was to examine the vasoconstrictive potential of D-lysergic acid using a bovine lateral (cranial branch) saphenous vein bioassay. Before testing lysergic acid, validation of the bovine lateral saphenous vein bioassay for use with a multimyograph apparatus was conducted using a dose-response to norepinephrine to evaluate the effects of limb of origin (right vs. left) and overnight storage on vessel contractile response. Segments (2 to 3 cm) of the cranial branch of the lateral saphenous vein were collected from healthy mixed breed cattle (n = 12 and n = 7 for the lysergic acid and norepinephrine experiments, respectively) at local abattoirs. Tissue was placed in modified Krebs-Henseleit, oxygenated buffer and kept on ice or stored at 2 to 8 degrees C until used. Veins were trimmed of excess fat and connective tissue, sliced into 2- to 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 degrees C). Tissue was allowed to equilibrate at 1 g of tension for 90 min before initiation of treatment additions. Increasing doses of norepinephrine (1 x 10(-8) to 5 x 10(-4) M) or lysergic acid (1 x 10(-11) to 1 x 10(-4) M) were administered every 15 min after buffer replacement. Data were normalized as a percentage of the contractile response induced by a reference dose of norepinephrine. Veins from both left and right limbs demonstrated contractions in a dose-dependent manner (P < 0.01) but did not differ between limbs. There were no differences in dose-response to norepinephrine between tissue tested the day of dissection and tissue tested 24 h later. Exposure of vein segments to increasing concentrations of lysergic acid did not result in an appreciable contractile response until the addition of 1 x 10(-4) M lysergic acid (15.6 +/- 2.3% of the 1 x 10(-4) M norepinephrine response). These data indicate that only highly elevated concentrations of lysergic acid result in vasoconstriction. Thus, in relation to the symptoms associated with vasoconstriction, lysergic acid may only play a minor role in the manifestation of fescue toxicosis.
authors.affiliation: Forage-Animal Production Research Unit, USDA-ARS, Lexington, KY 40546, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Klotz
authors.forename: L P
authors.initials: LP
authors.lastname: Bush
authors.forename: D L
authors.initials: DL
authors.lastname: Smith
authors.forename: W D
authors.initials: WD
authors.lastname: Shafer
authors.forename: L L
authors.initials: LL
authors.lastname: Smith
authors.forename: A C
authors.initials: AC
authors.lastname: Vevoda
authors.forename: A M
authors.initials: AM
authors.lastname: Craig
authors.forename: B C
authors.initials: BC
authors.lastname: Arrington
authors.forename: J R
authors.initials: JR
authors.lastname: Strickland
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods / Q000662:veterinary; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D005260:Female; D066298:In Vitro Techniques; D008237:Lysergic Acid / Q000737:chemistry / Q000494:pharmacology*; D008297:Male; D015394:Molecular Structure; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology; D015203:Reproducibility of Results; D012501:Saphenous Vein / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D014662:Vasoconstrictor Agents; D008237:Lysergic Acid; D009638:Norepinephrine