The effect of hypothermic ischemia on the α‐adrenergic mechanisms of the canine tibia vascular bed

Abstract

The effect of hypothermic ischemia on α-1 and -2 adrenergic receptor mediated vasoconstriction has been studied in an in vitro perfused canine tibia preparation. Bones were perfused at a constant rate with aerated (95% O₂, 5% CO₂) modified Krebs Ringer solution and the effect of bolus injections of norepinephrine (0.025–6.4 nmol) on the perfusion pressure was studied. For all bones the first dose-response curve was produced under control conditions. In one group the second dose-response curve was generated during a constant infusion of prazosin (α-1 adrenergic antagonist); in another it was produced during a constant infusion of rauwolscine (α-2 adrenergic antagonist); in the control group it was generated under control conditions. The results demonstrate that, after 48 h of hypothermic ischemia, α-1 adrenergic-mediated vasoconstriction was significantly attenuated (p < 0.001). However, α-2 adrenergic-mediated vasoconstriction was unaffected by increasing periods of hypothermic ischemia.