Figure 4. Effects of oxygen on arteriolar diameter and responses to methacholine. (A) Bars represent resting diameter/maximum diameter after equilibration with differing concentrations of oxygen and before application of methacholine. Vessel tone significantly decreased with decreasing oxygen concentration (P < 0.0001). (B) Bars represent average local response (in micrometers) to the application of methacholine. Local responses decreased with decreasing oxygen concentrations (P <0.0001). (C) Bars represent average conducted responses (in micrometers) at the 500-micro meter upstream location in response to methacholine. Conducted response decreased with decreasing oxygen concentrations (P <0.0001).