O2 metabolism in blood vessel walls with stenoses

Vascular tissue O₂ partial pressure (PO₂) measurements with recessed cathode O₂ microelectrodes were made in the walls of isolated rabbit abdominal aortas during saline perfusion in vitro. Three months prior to the experiments, the aortic lumen was reduced by approximately 50% using a tantalum metal clip. A 2- to 3-cm segment of the abdominal aorta including the stenosis was removed and mounted in a chamber maintained at 19.9 kPa. With constant perfusion, the minimum tissue PO₂ in the wall varied axially along the segment. The minimum wall PO₂ (±SE) was 13.5±0.4 kPa at the location 5 mm upstream and 14.2±0.8 kPa at the location 5 mm downstream. The lowest value, 11.6±0.8 kPa, was found 1 mm downstream. O₂ disappearance rates (d PO₂/dt) at each location were also measured after stopping perfusion to the segment. The disappearance rates varied axially, with the fastest rate, -4.1±0.6 kPa/min, found 1 mm upstream. At 4 and 5 mm upstream and downstream from the stenosis, the rates were essentially the same, at 2.8±0.3 kPa/min. The average value for O₂ metabolism at the upstream and downstream ends is 5.0×10^-4 mL O₂/mL tissue/min