Role of the Endothelium in the Reactivity of Bovine Isolated Digital Veins

Digital venoconstriction has been implicated in the development of laminitis. However, the in vitro reactivity of bovine isolated digital veins (BDV) is not entirely described. The response of BDV (n=10) to phenylephrine (PHE), acetylcholine (ACh) and sodium nitroprusside (SNP) was studied in endothelium-intact (E+) or denuded (E-) BDV using isometric tension recording. The effect of L–NAME (300 µM) and indometacine (10 µM) w as determined in E+ BDV. Relaxation responses to ACh and SNP were assessed in PHE-contracted rings.
Comparisons were performed using Student’s t tests. PHE response was not affected by the treatments. ACh caused relaxation (-53±5%) only in E+ BDV and contraction (14±3%) in E- rings. Treatment with L-NAME reduced (P<0.05) the response to ACh (-7±2%), suggesting that ACh-induced endothelium-dependent relaxation in BDV is primarily mediated by nitric oxide.
Indometacine did not reduce ACh-induced response significantly. Therefore, the contribution ...