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Journal of Animal Science, Vol 76, Issue 11 2853-2856, Copyright © 1998 by American Society of Animal Science

JOURNAL ARTICLE

Endophytic fungal toxin effect on adrenergic receptors in lateral saphenous veins (cranial branch) of cattle grazing tall fescue

J. W. Oliver, J. R. Strickland, J. C. Waller, H. A. Fribourg, R. D. Linnabary and L. K. Abney
Department of Comparative Medicine, University of Tennessee, Knoxville 37901, USA.

The objective of this research was to characterize the adrenergic receptor response in veins of cattle that grazed tall fescue (Festuca arundinacea Schreb.), with (E+) and without (E-) fungal endophyte (Neotyphodium coenophialum) infection. Measurement of contractile response of lateral saphenous veins to selective adrenergic receptor agonists (alphal, phenylephrine; alpha2, BHT-920) revealed enhanced reactivity (greater contractile response) only for the alpha2 adrenergic receptor in E+ pastured cattle. This response was consistent over a 3-yr grazing period. Significant contractility differences in response to BHT-920 occurred at concentrations of 3x10(-6) M and greater. Early research has reasoned that the enhanced reactivity is due to endophyte toxin effect on intracellular signaling systems. The enhanced contractile effect would alter blood flow dynamics and contribute to clinical signs and pathologic change in animals. The alpha2-adrenergic receptor is also involved in the control of many metabolic reactions. Thus, for drug therapy to be successful in reversing the adverse effects of E+ tall fescue exposure in cattle, effects on the alpha2-adrenergic tissue receptors must be neutralized.


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J. L. Klotz, B. H. Kirch, G. E. Aiken, L. P. Bush, and J. R. Strickland
Effects of selected combinations of tall fescue alkaloids on the vasoconstrictive capacity of fescue-naive bovine lateral saphenous veins
J Anim Sci, April 1, 2008; 86(4): 1021 - 1028.
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Copyright © 1998 by the American Society of Animal Science.