Measurements of vascular wall O2 consumption following increased potassium

Vascular wall tissue PO₂ was measured with recessed cathode microelectrodes (tip diameters <5 μm) in either strips or perfused segments of rabbit abdominal aortas (n=10). When bathed by saline with low K⁺ (4 mEq/L) oxygenated at 20 kPa, the minimum wall PO₂ was 6.65±1.56 (S.E.) kPa for seven aortic strips and 10.38±0.54 kPa for 16 measurements in three perfused aortic segments. Biphasic PO₂ increased significantly above control by +0.91±0.21 kPa (p<0.05), decreasing below control within 1 min in most cases. After 3 min, PO₂ decreased significantly below control by -0.72±0.24 kPa (p<0.05). O₂ disappearance rates measured after stopping flow to perfused segments were significantly faster (p<0.001) after relatively small changes in K⁺ (4 to 7 mEq/L) with little further increase at higher K⁺ up to 30 mEq/L. The data are consistent with elevated O₂ consumption as K⁺ increases. Perfused aortic segments had much greater metabolic changes than aortic strips for similar K⁺ increases