Different reactivity of two rabbit vessels under hypoxia

The effect of hypoxia on isolated rabbit vessel reactivity to vasoconstrictive agents was studied. Short-lasting hypoxia (30 min.) enhanced the responses to noradrenaline, 5-hydroxytryptamine, histamine and endothelin in the ear artery. Increased reactivity was also found with KCl depolarization solution. Deendothelization of the ear artery did not influence the enhanced responses to noradrenaline and endothelin in hypoxia. In similar experimental conditions the femoral artery reactivity to noradrenaline was not affected by hypoxia, the constrictory responses to 5-hydroxytryptamine were decreased. It can be concluded that hypoxic facilitation of vasoconstrictive activity is probably independent on receptor-related mechanisms and/or on the presence of endothelium. The results obtained confirm also the difference in reactivity of rabbit vessels from two vascular beds to vasoconstrictive agents under hypoxia.