Assessment of vasoconstrictive potential of D-lysergic acid using an isolated bovine lateral saphenous vein bioassay1

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.

BOARD-INVITED REVIEW: St. Anthony's Fire in livestock: Causes, mechanisms, and potential solutions1,2

“…However, a series of studies have been published recently that examined the potency and efficacy of selected ergot alkaloids to induce constriction of the bovine lateral saphenous vein in vitro (Klotz et al, 2006(Klotz et al, , 2007(Klotz et al, , 2008(Klotz et al, , 2010. Ergovaline was shown to be approximately 1,000-fold more potent and 5-fold more efficacious in causing vasoconstriction than lysergic acid (Klotz et al, 2006(Klotz et al, , 2007. Ergotamine and ergovaline reportedly have very similar contractile dose response curves (Klotz et al, 2007).…”

“…Although potency and efficacy studies are routinely conducted on drugs, the study of ergot alkaloid potency and efficacy in the vasculature system of livestock has not received a great deal of attention. However, a series of studies have been published recently that examined the potency and efficacy of selected ergot alkaloids to induce constriction of the bovine lateral saphenous vein in vitro (Klotz et al, 2006(Klotz et al, , 2007(Klotz et al, , 2008(Klotz et al, , 2010. Ergovaline was shown to be approximately 1,000-fold more potent and 5-fold more efficacious in causing vasoconstriction than lysergic acid (Klotz et al, 2006(Klotz et al, , 2007.…”

A vascular contractility bioassay using bovine right ruminal artery and vein1,2

“…Accepted January 19, 2011 arundinaceum) toxicosis syndrome, and ergot alkaloids produced by the fungus Neotyphodium coenophialum have been demonstrated as causative agents of vasoconstriction (Strickland et al, 2009). Much of in the vitro research demonstrating this has been done using peripheral blood vessels (Williams et al, 1975;Solomons et al, 1989;Klotz et al, 2006), and of the few available in vivo reports investigating fescue toxicosis and ergot alkaloids (Walls and Jacobson, 1970;Harmon et al, 1991;Rhodes et al, 1991;Aiken et al, 2007), only Rhodes et al (1991) and Harmon et al (1991) have evaluated blood fiow to viscera. Delineating how ergot alkaloids are absorbed and transported from the digestive tract to the affected peripheral tissues has been elusive.…”

Fescue toxicosis and its influence on the rumen microbiome: mitigation of production losses through clover isoflavones

“…The authors determined that including yeast-derived cell wall improved serum prolactin post-calving in cows, and may alleviate concerns with high-alkaloid tall fescue, however, excretion of lysergic acid and ergovaline were not affected by the yeast-derived cell wall treatment. Klotz et al (2006) concluded that ergovaline is exponentially more powerful in stimulating vasoconstriction within in vitro bovine vasculature compared to lysergic acid, and more potent throughout host physiology as a whole. Ruminal microorganisms interact with feedstuffs in three established ways: those within the ruminal fluid, those loosely attached to feed particles and those firmly attached to feedstuffs (Cheng and McAllister 1997), thus breakdown of feedstuffs is essential for several types of microorganisms to access nutrients.…”