Figure 4. Local increases in ${\mathit{}\mathit{P}}_{{\mathrm{O}}_2}$ have no effect on arteriolar tone in occluded arterioles .

A, a preparation similar to that depicted in Fig. 3, but with the inclusion of an occluding pipette that was pressed down on the arteriole to eliminate blood flow through the aparenchymal segment. B, summary data from these experiments (data are means ± SEM, n = 5). Local changes in $P_{{\mathrm{O}}_2}$ across the arteriolar wall produced by the fluid‐filled pipette (Local) were ineffective in producing arteriolar constriction. However, raising the $P_{{\mathrm{O}}_2}$ of the superfusate over the entire preparation (Global) produced consistent, sustained arteriolar constriction. These data, along with those shown in Fig. 3, suggest that components of the arteriolar wall (endothelial cells, smooth muscle cells or perivascular nerves) are not the sensor cells responsible for arteriolar O₂ reactivity in the hamster cheek pouch. Data are replotted from Fig. 4 B in Jackson (1987); see this reference for more details.