Rate of Decrease of PO2 from an Arteriole with Arrested Flow

Abstract

When flow to a region is arrested, the amount of oxygen contained within the stationary blood decreases at a rate dependent on the oxygen utilization of the surrounding tissue. We used phosphorescence quenching microscopy to measure arteriolar PO₂ in the mesentery of male Sprague-Dawley rats. Flow was quickly stopped (< 1 s) by occluding the microvessels using an inflatable Saran bag attached to the microscope objective. The rate of decline in PO₂ following occlusion yielded a calculated initial flux of oxygen out of the vessel lumen of 8.0 × 10⁻⁷ ml O₂ cm⁻² sec⁻¹. An upper limit on the oxygen consumption of the arteriolar wall was calculated by assuming that all of the oxygen in the lumen was consumed by the wall at the initial rate. This value was 2.5 × 10⁻³ ml O₂ cm⁻³ sec⁻¹ and is an overestimate since the oxygen consumption of the nearby parenchymal cells was neglected. The calculated maximum oxygen consumption of the wall is more than an order of magnitude smaller than that reported previously for arterioles in the rat mesentery (6.5 × 10⁻² ml O₂ cm⁻³ sec⁻¹). We conclude that oxygen consumption of the arteriolar wall is similar to previous values for other vascular tissues.