Po2 profiles near arterioles and tissue oxygen consumption in rat mesentery

Abstract

A scanning phosphorescence quenching microscopy technique, designed to prevent accumulated O2 consumption by the method, was applied to Po2 measurements in mesenteric tissue. In an attempt to further increase the accuracy of the measurements, albumin-bound probe was topically applied to the tissue and an objective-mounted pressurized bag was used to reduce the oxygen transport bypass through the thin layer of fluid over the mesentery. Po2 was measured at multiple sites perpendicular to the blood/wall interface in the vicinity of 84 mesenteric arterioles (7–39 μm in diameter) at distances of 5, 15, 30, 60, 120, and 180 μm in seven anesthetized Sprague-Dawley rats, thereby creating Po2 profiles. Interstitial Po2 above and immediately beside arterioles was found to agree with known intravascular values. No significant difference in Po2 profiles was found between small and large arterioles, indicating a small longitudinal Po2 gradient in the precapillary mesenteric microvasculature. In addition, the Po2 profiles were used to calculate oxygen consumption in the mesenteric tissue (56–65 nl O2·cm−3·s−1). Correction of these values for contamination with ambient oxygen yielded an oxygen consumption rate of 60–68 nl O2·cm−3·s−1, the maximal limit for consumption in the mesentery. The results were compared with measurements made by other workers in regard to the employed techniques.