Oxygen disappearance curves (ODCs) recorded in arterioles after rapid arrest of blood flow reflect the complex interaction among the dissociation of O2 from hemoglobin, O2 diffusivity and rate of respiration in the vascular wall and surrounding tissue. Analysis of ODCs allows estimation of parameters of O2 transport and O2 consumption in the microcirculation. ODCs were collected from rapidly arrested blood inside rat mesenteric arterioles using scanning phosphorescence quenching microscopy (PQM). The technique was employed to prevent the artifact of accumulated O2 photoconsumption in stationary media. The ODC signatures were linear in contrast to a reported exponential decline of intraarteriolar PO2. The rate of O2 disappearance was 0.43 mmHg/s in 20 μm diameter arterioles. The duration of the ODC was 290 s, much longer than the 12.8 s reported by others. Arterioles associated with lymphatics had a higher O2 disappearance rate of 0.73 mmHg/s. The O2 flux from arterioles was 0.21 nl O2/(cm2•s), two orders of magnitude lower than previously reported. The upper limit of O2 consumption by the arteriolar wall, calculated from the condition that all the O2 is consumed by the wall, was 452 nl O2/(cm3 s). From the microvascular tissue volume fraction in the rat mesentery of 6%, the estimated respiration rate of the vessel wall is about 30 nl O2/(cm3 s). This result is three orders of magnitude lower than the value reported by others. Our results demonstrate that oxygen loss from mesenteric arterioles is small and oxygen consumption by the arteriolar wall is not unusually large.
- oxygen consumption
- phosphorescence quenching microscopy
- Copyright © 2011, American Journal of Physiology - Heart and Circulatory Physiology