The oxygen environment of the arterial media in early rabbit hypertension

Hypertensive stimuli in experimental animals appear to cause early arterial wall hypermetabolism before hypertension is established and before histomorphic changes are marked. Hypermetabolism and the large diffusion distances for oxygen characteristic of large arteries imply that mural hypoxia could occur early in the disease but this has not been studied. Therefore, we measured aortic wall tissue oxygen distributions in male New Zealand White rabbits 2 weeks (1) after production of upper body hypertension by coarctation of the abdominal aorta, (2) after sham operation, and (3) in normal controls. As compared to normal and sham operated animals, blood pressure in the coarctation animals was significantly elevated from control levels, and the oxygen partial pressures were significantly reduced throughout the media. However, the hypoxic mural oxygen tensions in this relatively thin wall were not low enough to terminate classical respiration. At the time of measurement, moderate microscopic pathology was already present, including increased connective tissue production. The accompanying histomorphic changes are compatible with reports of extrarespiratory oxygen sensitivity of connective tissue metabolism.