Role of oxygen in autoregulation of blood flow in isolated vessels

Abstract

The role of oxygen in control of local blood flow was investigated in isolated arterial segments 1 cm in length and 0.5–1.0 mm in diameter by perfusion with blood of various Po₂ levels. A decrease in vascular resistance always occurred when the Po₂ was lowered and an increase occurred when it was raised. In 20 vessels, using constant-pressure perfusion, an average increase in conductance of 2.38 times normal level was obtained when the Po₂ was lowered from 100 to 30 mm Hg. When this datum was plotted according to initial flow, the smaller vessels gave the greatest response to low oxygen (2.73 times normal; sem ± 0.15), whereas the largest gave the least (1.76 times normal; sem ± 0.10). Forty-three vessels perfused under constant-flow conditions gave results which were consistent with and confirmed the constant-pressure results. In all of these experiments pH, Pco₂, and temperature were monitored and kept at physiological levels. The results indicate that oxygen could well be a factor in the autoregulation of blood flow.