Cell and oxygen flow in arterioles controlling capillary perfusion.

Measurements of hemodynamic and oxygen transport characteristics in the arterioles that control capillary perfusion in striated muscle were used to compare oxygen flow into adjacent capillary networks. Observations were made in arterioles arising consecutively (branches 1-3 and the last branch) from a single transverse arteriole. During maximal dilation [after 5 min of exposure to superfusate with 10(-4) M adenosine (ADO)], mean cell flow into branches decreased significantly with increasing axial distance along the transverse arteriole, from 8.47 +/- 2.43 x 10(3) (SE) cells/s in branch 1 to 5.56 +/- 2.14 x 10(3), 3.21 +/- 1.30 x 10(3), and 4.00 +/- 1.33 x 10(3) cells/s in successive branches. During control, cell fluxes were not significantly different by position (2.21 +/- 1.12, 1.31 +/- 0.42, 0.97 +/- 0.31, and 1.23 +/- 0.40 cells/s in branches 1, 2, and 3 and the last branch, respectively). Branch diameters during ADO were not significantly different by position (26.2 +/- 2.9, 24.5 +/- 1.4, 22.0 +/- 2.8, and 26.7 +/- 2.7 microns, respectively). Hemoglobin saturations during ADO were not different (59.6 +/- 2.2, 60.6 +/- 2.3, 60.3 +/- 2.3, and 61.0 +/- 2.3%, respectively), whereas mean oxygen flow into branch 1 significantly exceeded that into branches 2 and 3 and the last branch (1.40 +/- 0.40 vs. 0.60 +/- 0.17, 0.53 +/- 0.22, and 0.66 +/- 0.22 pl/min, respectively). During control, oxygen flows were not significantly different between branches. Thus, both cell and oxygen flow into these arterioles vary in a systematic way dependent on their relative branch position; regulatory processes serve to make oxygen supply more uniform.