Location: Forage-animal Production ResearchTitle: Tall fescue alkaloids cause vasoconstriction in equine medial palmar artery and vein Author
Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract Only
Publication Acceptance Date: 2/25/2010
Publication Date: 7/11/2010
Citation: Klotz, J.L., Mcdowell, K.J. 2010. Tall fescue alkaloids cause vasoconstriction in equine medial palmar artery and vein. J. Anim. Sci. 88(2/J). Dairy Sci. 93(1)/Poult. Sci. 89(1):55. Interpretive Summary:
Technical Abstract: Mares grazing endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum) typically exhibit reproductive dysfunction rather than peripheral vasoconstriction as a primary sign of the fescue toxicosis syndrome. Recent work using Doppler ultrasonography demonstrated that consumption of endophyte-infected tall fescue seed causes measurable vasoconstriction in the medial palmar artery. The objective of this study was to evaluate contractile responses of medial palmar artery (PA) and vein (PV) to increasing concentrations of alkaloids, ergotamine (ERT), ergonovine (ERN), ergocryptine (ERP), ergocristine (ERS), ergocornine (ERO), and lysergic acid (LSA) and biogenic amines norepinephrine (NE) and 5-hydroxytryptamine (5HT). Medial PA and PV were collected immediately following euthanasia from 18 horses of mixed breed, age and gender along the third metacarpal proximal to the fetlock joint from both forelimbs and placed in modified Krebs-Henseleit buffer. Vessels were separated, cleaned of excess connective and adipose tissue, divided into 2-3 mm cross-sections and suspended in a multi-myograph chamber with continuously oxygenated Krebs-Henseleit buffer (95%O2/5%CO2; pH=7.4; 37'C). Following a 90-min equilibration and recovery from a 1x10-4 M NE reference addition, increasing concentrations of each compound were added every 15 or 20 min for PV and PA, respectively. Data were normalized as a % contractile response induced by the 10-4 M NE addition. Response between PA and PV for alkaloid or biogenic amine did not differ. All alkaloids produced a contractile response, except neither PA nor PV responded to LSA. Both NE and 5HT had a 2-fold greater maximal response than all alkaloids in both PA and PV (P<0.05), ERN had the greatest response in the PV, and ERN and ERO had greatest maximal responses in PA (P<0.05). Although horses do not outwardly appear to be affected by peripheral vasoconstriction as observed in cattle, these data indicate that tall fescue alkaloids are vasoactive and suggest that potential exists for peripheral vascular effects of tall fescue alkaloids in horses.