title: Oxygen release from arterioles with normal flow and no-flow conditions.
abstract: The rate of oxygen release from arterioles ( approximately 55 microm diameter) was measured in the hamster window chamber model during flow and no-flow conditions. Flow was stopped by microvascular transcutaneous occlusion using a glass pipette held by a manipulator. The reduction of the intra-arteriolar oxygen tension (Po2) was measured by the phosphorescence quenching of preinfused Pd-porphyrin, 100 microm downstream from the occlusion. Oxygen release from arterioles was found to be 53% greater during flow than no-flow conditions (2.6 vs. 1.7 x 10(-5) ml O2.cm(-2).s(-1), P < 0.05). Acute hemodilution with dextran 70 was used to reduce vessel oxygen content, significantly increase wall shear stress (14%, P < 0.05), reduce Hct to 28.4% (SD 1.0) [vs. 48.8% (SD 1.8) at baseline], lower oxygen supply by the arterioles (10%, P < 0.05), and increase oxygen release from the arterioles (39%, P < 0.05). Hemodilution also increased microcirculation oxygen extraction (33% greater than nonhemodilution, P < 0.05) and oxygen consumption by the vessel wall, as shown by an increase in vessel wall oxygen gradient [difference in Po2 between the blood and the tissue side of the arteriolar wall, nonhemodiluted 16.2 Torr (SD 1.0) vs. hemodiluted 18.3 Torr (SD 1.4), P < 0.05]. Oxygen released by the arterioles during flow vs. nonflow was increased significantly after hemodilution (3.6 vs. 1.8 x 10(-5) ml O2.cm(-2).s(-1), P < 0.05). The oxygen cost induced by wall shear stress, suggested by our findings, may be >15% of the total oxygen delivery to tissues by arterioles during flow in this preparation.
authors.affiliation: La Jolla Bioengineering Institute, University of California-San Diego, La Jolla, CA 92037, USA. pcabrales@ucsd.edu
authors.forename: Pedro
authors.initials: P
authors.lastname: Cabrales
authors.forename: Amy G
authors.initials: AG
authors.lastname: Tsai
authors.forename: Paul C
authors.initials: PC
authors.lastname: Johnson
authors.forename: Marcos
authors.initials: M
authors.lastname: Intaglietta
mesh_terms: D000818:Animals; D001160:Arterioles / Q000378:metabolism*; D001775:Blood Circulation / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology; D001784:Blood Gas Analysis; D006224:Cricetinae; D006400:Hematocrit; D006438:Hemodilution; D006439:Hemodynamics / Q000502:physiology; D008647:Mesocricetus; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology
chemical_list: D010100:Oxygen