Rate of Decrease of PO2 from an Arteriole with Arrested Flow

Pittman, Roland N.; Golub, Aleksander S.; Schleicher, William F.

doi:10.1007/0-387-26206-7_34

Cited by 10 publications

(15 citation statements)

References 13 publications

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“…Our results are consistent with measurements made by different methods in connective tissue (including aortic wall and aortic valve cusp) and lower than V O2 in muscles (3,4,10,19,20,32,41,45). A-V, arteriovenous.…”

Section: Discussionsupporting

confidence: 95%

Po₂profiles near arterioles and tissue oxygen consumption in rat mesentery

Golub

Barker²,

Pittman³

2007

American Journal of Physiology-Heart and Circulatory Physiology

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A scanning phosphorescence quenching microscopy technique, designed to prevent accumulated O(2) consumption by the method, was applied to Po(2) 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. Po(2) was measured at multiple sites perpendicular to the blood/wall interface in the vicinity of 84 mesenteric arterioles (7-39 microm in diameter) at distances of 5, 15, 30, 60, 120, and 180 microm in seven anesthetized Sprague-Dawley rats, thereby creating Po(2) profiles. Interstitial Po(2) above and immediately beside arterioles was found to agree with known intravascular values. No significant difference in Po(2) profiles was found between small and large arterioles, indicating a small longitudinal Po(2) gradient in the precapillary mesenteric microvasculature. In addition, the Po(2) profiles were used to calculate oxygen consumption in the mesenteric tissue (56-65 nl O(2) x cm(-3) x s(-1)). Correction of these values for contamination with ambient oxygen yielded an oxygen consumption rate of 60-68 nl O(2) x cm(-3) x 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.

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Section: Discussionsupporting

confidence: 95%

Po₂profiles near arterioles and tissue oxygen consumption in rat mesentery

Golub

Barker²,

Pittman³

2007

American Journal of Physiology-Heart and Circulatory Physiology

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“…Our interest in the mesentery was associated with the ability to examine individual microvessels as well as to compare our results with previously published reports (37) claiming an exceptionally high rate of V O 2 in the wall of arterioles and in the surrounding connective tissue. The mean inner diameter of the arterioles (ϳ20 m) from this study allows a comparison with results on the O 2 loss from 25-m mesenteric arterioles and fourth-order (A4; 24 m) arterioles in a hamster muscle (22,25,26). Mesenteric arterioles are surrounded by a thin sheet of connective tissue having relatively low V O 2 (13), which more readily reveals the contribution of vascular wall respiration to the O 2 loss from arterioles.…”

Section: Discussionmentioning

confidence: 76%

“…The PO 2 time course recorded in stopped blood can be used for the calculation of O 2 flux from the vessel lumen and the rate of V O 2 in the vascular wall. This experiment was conducted in microvessels of the rat mesentery and revealed a relatively slow PO 2 fall in 46-and 25-m-inner diameter arterioles with rates of 0.29 and 0.36 mmHg/s (lifetimes were ϳ126 and 43 s, respectively) (22 , or 25 times lower than the reported value based on the transmural PO 2 difference (37).…”

mentioning

confidence: 73%

“…The air bag of plastic film mounted on the objective lens allows one to manipulate blood flow using this classic technique (13,22). In the time between recordings of the ODCs in selected arterioles, the pressure in the bag was maintained in the range of 5-10 mmHg to ensure a snug fit of the Ten animals were used for intravascular measurements of the rate of O2 disappearance from arterioles and four animals were used for the scanned PO2 profiles in perivascular mesenteric tissue.…”

Section: Methodsmentioning

confidence: 99%

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The rate of O₂loss from mesenteric arterioles is not unusually high

Golub

Song

Pittman

2011

American Journal of Physiology-Heart and Circulatory Physiology

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Golub AS, Song BK, Pittman RN. The rate of O2 loss from mesenteric arterioles is not unusually high. Am J Physiol Heart Circ Physiol 301: H737-H745, 2011. First published June 17, 2011 doi:10.1152/ajpheart.00353.2011The O 2 disappearance curve (ODC) recorded in an arteriole after the rapid arrest of blood flow reflects the complex interaction among the dissociation of O 2 from hemoglobin, O 2 diffusivity, and rate of respiration in the vascular wall and surrounding tissue. In this study, the analysis of experimental ODCs allowed the estimation of parameters of O 2 transport and O2 consumption in the microcirculation of the mesentery. We collected ODCs from rapidly arrested blood inside rat mesenteric arterioles using scanning phosphorescence quenching microscopy (PQM). The technique was used to prevent the artifact of accumulated O 2 photoconsumption in stationary media. The observed ODC signatures were close to linear, in contrast to the reported exponential decline of intra-arteriolar PO 2. The rate of PO2 decrease was 0.43 mmHg/s in 20-m-diameter arterioles. The duration of the ODC was 290 s, much longer than the 12.8 s reported by other investigators. The arterioles associated with lymphatic microvessels had a higher O 2 disappearance rate of 0.73 mmHg/s. The O 2 flux from arterioles, calculated from the average O 2 disappearance rate, was 0.21 nl O2·cmϪ2 ·s Ϫ1 , two orders of magnitude lower than reported in the literature. The physical upper limit of the O 2 consumption rate by the arteriolar wall, calculated from the condition that all O 2 is consumed by the wall, was 452 nl O 2·cm Ϫ3 ·s Ϫ1 . From consideration of the microvascular tissue volume fraction in the rat mesentery of 6%, the estimated respiration rate of the vessel wall was ϳ30 nl O 2·cm Ϫ3 ·s Ϫ1 . This result was three orders of magnitude lower than the respiration rate in rat mesenteric arterioles reported by other investigators. Our results demonstrate that O 2 loss from mesenteric arterioles is small and that the O2 consumption by the arteriolar wall is not unusually large. microcirculation; arterioles; oxygen consumption; phosphorescence quenching microscopy CAPILLARIES PLAY A CENTRAL ROLE in the diffusive O 2 supply to parenchymal cells, as envisioned by Krogh (18,19). For half a century after Krogh's breakthrough, this concept stood as a pillar of experimental research and mathematical modeling of O 2 transport to tissue. Forty years ago, the experimental findings of a longitudinal gradient of PO 2 in arterioles undermined the absolutism of the central role of capillaries and demonstrated the possibility of substantial O 2 loss from blood before it enters the capillaries (5). Longitudinal gradients of O 2 content and partial pressure in arteriolar blood were reported by independent researchers with different measuring techniques (20,21,25,26,37) and were reviewed in Refs. 17 and 38. The contribution of arterioles to the diffusion of O 2 from blood to tissue was established experimentally and received theoretical substantiation (24). Fur...

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“…The high value reported by Pittman was calculated using the arrested flow method. 26 We believe that they reported the maximum value for wall consumption by assuming that all of the oxygen disappeared from the arteriolar lumen, thereby setting an upper limit on M. Differences in the values of various reports might result from differences in the targeted tissues or measurement methods. Because the arteriolar wall comprises various cell types (endothelium, smooth muscle cells, and pericytes) and matrices (basement membrane, collagen, and elastin), the results show that the vessel wall functions partly as a barrier to oxygen and partly as a permeable membrane.…”

Section: Oxygen Balance (Consumption and Diffusion)mentioning

confidence: 98%

A New Method for Measuring the Oxygen Diffusion Constant and Oxygen Consumption Rate of Arteriolar Walls

et al. 2012

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Oxygen transport is believed to primarily occur via capillaries and depends on the oxygen tension gradient between the vessels and tissues. As blood flows along branching arterioles, the O 2 saturation drops, indicating either consumption or diffusion. The blood flow rate, the O 2 concentration gradient, and Krogh's O 2 diffusion constant (K) of the vessel wall are parameters affecting O 2 delivery. We devised a method for evaluating K of arteriolar wall in vivo using phosphorescence quenching microscopy to measure the partial pressure of oxygen in two areas almost simultaneously. The K value of arteriolar wall (inner diameter, 63.5 ± 11.9 μm; wall thickness, 18.0 ± 1.2 μm) was found to be 6.0 ± 1.2 × 10 −11 (cm 2 /s)(ml O 2 ·cm −3 tissue·mmHg −1 ). The arteriolar wall O 2 consumption rate (M) was 1.5 ± 0.1 (ml O 2 ·100 cm −3 tissue·min −1 ), as calculated using Krogh's diffusion equation. These results suggest that the arteriolar wall consumes a considerable proportion of the O 2 that diffuses through it. (Keio J Med 61 (2) : 57-65, June 2012)

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Rate of Decrease of PO2 from an Arteriole with Arrested Flow

Cited by 10 publications

References 13 publications

Po₂profiles near arterioles and tissue oxygen consumption in rat mesentery

Po₂profiles near arterioles and tissue oxygen consumption in rat mesentery

The rate of O₂loss from mesenteric arterioles is not unusually high

A New Method for Measuring the Oxygen Diffusion Constant and Oxygen Consumption Rate of Arteriolar Walls

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Rate of Decrease of PO2 from an Arteriole with Arrested Flow

Cited by 10 publications

References 13 publications

Po2profiles near arterioles and tissue oxygen consumption in rat mesentery

Po2profiles near arterioles and tissue oxygen consumption in rat mesentery

The rate of O2loss from mesenteric arterioles is not unusually high

A New Method for Measuring the Oxygen Diffusion Constant and Oxygen Consumption Rate of Arteriolar Walls

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Po₂profiles near arterioles and tissue oxygen consumption in rat mesentery

Po₂profiles near arterioles and tissue oxygen consumption in rat mesentery

The rate of O₂loss from mesenteric arterioles is not unusually high