Effect of hypoxia/reoxygenation on the contractility of the isolated bovine digital vein.

The bovine digital vasculature contractility has been implicated in the development of laminitis. To investigate the effect of hypoxia/reoxygenation on the contractility of isolated peripheral bovine digital veins (BDVs), vessel rings were studied under isometric conditions and submitted to 30 min of hypoxia (95%N(2)-5%CO(2)) and reoxygenation (95%O(2)-5%CO(2)) conditions, respectively. The BDVs contracted with a high K(+) depolarizing solution, developed hypoxia-induced relaxation, followed by an increase in tension upon reoxygenation. In contrast, phenylephrine-contracted BDVs displayed a rapid, sustained and reversible hypoxia-induced contraction. Reoxygenation caused a rapid relaxation in phenylephrine-contracted BDVs. The presence of the endothelium did not modify the hypoxia/reoxygenation effects and hypoxia-induced contraction was still observed in a nominal Ca(2+)-free Krebs, however, the last effect was not maintained over time. The hypoxia-induced contraction in an isolated peripheral vein may contribute to the understanding of the physiology and pathophysiology of superficial venous smooth muscle contractility, particularly in the alteration of bovine digital haemodynamics under hypoxia/reoxygenation conditions.