Assessment of vasoconstrictive capacity of tasll fescue alkaloids using fescue naive lateral saphenous veins of crossbred heifer cattle

Abstract

Vasoconstriction is one response associated with consumption of toxic endophyte-infected tall fescue. Because it is not known if endophyte-produced alkaloids act alone or collectively, the objective of this study was to examine the vasoconstrictive potentials of D-lysergic acid, ergovaline, and N-acetylloline individually or in paired combinations using bovine lateral saphenous veins biopsied from fescue naïve cattle. Segments (2- 3 cm) of vein were surgically biopsied from healthy Brahmaninfluenced yearling cattle (n=22; 330 ± 8 kg). The data indicated that ergovaline is a more potent vascular toxicant than lysergic acid and N-acetylloline. Further, the presence of N-acetylloline did not inhibit or potentiate the effects of the ergot alkaloids on vascular activity. The contractile responses of the remaining combinations did appear to differ from the individual concentration responses. This supports the possibility that a combinatorial or repetitive alkaloid exposure effect may exist in vivo and should be considered during in vitro evaluations of ergot alkaloids. Keywords: fescue-naïve cattle, fescue toxicosis, vasoconstriction