Flow-induced oxygen uptake by the perfused rat hindlimb is inhibited by vasodilators and augmented by norepinephrine: a possible role for the microvasculature in hindlimb thermogenesis

Ye, Ji-Ming; Colquhoun, Eric Q.; Hettiarachchi, Manthinda; Clark, Michael G.

doi:10.1139/y90-018

Cited by 27 publications

(21 citation statements)

References 32 publications

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“…They have argued that the increase in vo, can be attributed to the increase in metabolic activity of the arteriolar resistance vessels associated with smooth muscle contraction (e.g. Ye et al 1989). They have noted that the voz of microvessels is much greater than that of larger conduit vessels in whrch most of the measurements have been made: the voo, of isolated cerebral microvessels was found to be as high as 1.6 pmol min-' g-' or 0.031 ml min-' g-' and increased 3-fold when succinate was given as substrate (Sussman et al 1988).…”

Section: Chronically Hypoxic Ratsmentioning

confidence: 99%

The effects of acute and chronic systemic hypoxia on muscle oxygen supply and oxygen consumption in the rat

Marshall¹,

Davies²

1999

Experimental Physiology

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SUMMARYThe aims of the present study were to evaluate how acute systemic hypoxia affects 0, delivery to skeletal muscle and muscle 0, consumption (voJ of the rat and to establish how these relationships are altered by chronic systemic hypoxia. Thus, the effects of breathing different concentrations of 0, (air, 12 % and 8 % 0,) upon oxygen delivery and vo, were studied in hindlimb muscles of control, normoxic (N) rats and of rats that had been made chronically hypoxic in a chamber at 12 % 0, for 3-4 weeks (CH) rats. Under anaesthesia, arterial blood pressure, femoral blood flow (FBF), arterial 0, content (Ca,02) and venous 0, content in the efflux from hiindlimb were measured. In N rats, changing the inspirate from air to 12 YO and 8 % 0, for 5 min each, reduced C,,,? from 20 f 0.3 ml (100 ml)-' in air to 13 f 1.0 ml (100 ml)-' in 8 % 0,. FBF did not change significantly (1.7 f 0.1 ml m i d in air) so that 0, delivery to hindlimb muscles fell from 0.28 f 0.07 to 0.16 f 0.02 ml min-' in 8 % 0,. Nevertheless, the-??, of hindlimb muscles was well maintained: 0.06 & 0.02 ml min-' in air and 0.08 k 0.02 ml min in 8 % 0,. In CH rats breathing 12 % 0,, Ca,02 (23 f 1.0 ml (100 ml)-') was comparable to that of N rats breathing air, due to an increase in haematocrit, as were FBF (1.6 f 0.2 ml m i d ) and 0, delivery (0.39 f 0.05 ml min-').However, vo2 was 2.5-fold greater in CH rats (0.16 f 0.03 ml min-'). As in N rats, FBF was well maintained at 1.7 f 0.2 and 1.6 f 0.2 ml min-' in 8 % 0, and air, respectively. Further, 3 was also well maintained, at 0.17 f 0.02 and 0.12 f 0.02 ml min-' in 8 % 0, and air, respectively.These results suggest that, contrary to previous reports, muscle vo2 of the rat is independent of 0, delivery over a wide range of 0, delivery values. They also sugges: that muscle Vo, #of CH rats is similarly independent of 0, delivery. The novel finding that muscle Voz has a greater absolute value in CH rats can, we propose, be explained by an increase in voz of the vasculature rather than of the skeletal muscle fibres and reflects increased biosynthetic activity of the vessel walls and/or vascular remodelling. 0 2 .

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Section: Chronically Hypoxic Ratsmentioning

confidence: 99%

The effects of acute and chronic systemic hypoxia on muscle oxygen supply and oxygen consumption in the rat

Marshall¹,

Davies²

1999

Experimental Physiology

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“…The reported rates of O 2 loss from arterioles were found to be an order of magnitude higher than expected, based on a theoretical analysis of diffusion through the vessel wall. At the same time, the hypothesis of "hot pipes" was proposed for a possible role of the microvasculature in organ thermogenesis due to the extremely high rate of O 2 consumption (V O 2 ) in the arteriolar wall (43). Experimental evidence supporting that hypothesis was obtained in arterioles of the rat mesentery with the application of phosphorescence quenching microscopy (PQM) to PO 2 measurements inside and outside of an arteriole (37 Ϫ3 ·s Ϫ1 ) was later reported by independent investigators for the rat cremaster muscle (32).…”

mentioning

confidence: 99%

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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“…Experiments performed in the rat mesentery have indicated the existence of a substantial oxygen gradient in mesenteric arterioles (54,64,65). In these studies, the hypothesis was put forth that the vascular tissue has a very high metabolic rate and serves as the primary sink for the oxygen transported by blood.…”

mentioning

confidence: 99%

Microvascular oxygen tension in the rat mesentery

Golub¹,

Barker²,

Pittman³

2008

American Journal of Physiology-Heart and Circulatory Physiology

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Longitudinal Po(2) profiles in the microvasculature of the rat mesentery were studied using a novel phosphorescence quenching microscopy technique that minimizes the accumulated photoconsumption of oxygen by the method. Intravascular oxygen tension (Po(2), in mmHg) and vessel diameter (d, in microm) were measured in mesenteric microvessels (n = 204) of seven anesthetized rats (275 g). The excitation parameters were as follows: 7 x 7-microm spot size; 410 nm laser; and 100 curves at 11 pulses/s, with pulse parameters of 2-micros duration and 80-pJ/microm(2) energy density. The mean Po(2) (+/- SE) was 65.0 +/- 1.4 mmHg (n = 78) for arterioles (d = 18.8 +/- 0.7 microm), 62.1 +/- 2.0 mmHg (n = 38) at the arteriolar end of capillaries (d = 7.8 +/- 0.3 microm), and 52.0 +/- 1.0 mmHg (n = 88) for venules (d = 22.5 +/- 1.0 microm). There was no apparent dependence of Po(2) on d in arterioles and venules. There were also no significant deviations in Po(2) based on d (bin width, 5 microm) from the general mean for both of these types of vessels. Results indicate that the primary site of oxygen delivery to tissue is located between the smallest arterioles and venules (change of 16.3 mmHg, P = 0.001). In conclusion, oxygen losses from mesenteric arterioles and venules are negligible, indicating low metabolic rates for both the vascular wall and the mesenteric tissue. Capillaries appear to be the primary site of oxygen delivery to the tissue in the mesenteric microcirculation. In light of the present results, previously reported data concerning oxygen consumption in the mesenteric microcirculation can be explained as artifacts of accumulated oxygen consumption due to the application of instrumentation having a large excitation area for Po(2) measurements in slow moving and stationary media.

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Flow-induced oxygen uptake by the perfused rat hindlimb is inhibited by vasodilators and augmented by norepinephrine: a possible role for the microvasculature in hindlimb thermogenesis

Cited by 27 publications

References 32 publications

The effects of acute and chronic systemic hypoxia on muscle oxygen supply and oxygen consumption in the rat

The effects of acute and chronic systemic hypoxia on muscle oxygen supply and oxygen consumption in the rat

The rate of O₂loss from mesenteric arterioles is not unusually high

Microvascular oxygen tension in the rat mesentery

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Flow-induced oxygen uptake by the perfused rat hindlimb is inhibited by vasodilators and augmented by norepinephrine: a possible role for the microvasculature in hindlimb thermogenesis

Cited by 27 publications

References 32 publications

The effects of acute and chronic systemic hypoxia on muscle oxygen supply and oxygen consumption in the rat

The effects of acute and chronic systemic hypoxia on muscle oxygen supply and oxygen consumption in the rat

The rate of O2loss from mesenteric arterioles is not unusually high

Microvascular oxygen tension in the rat mesentery

Contact Info

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Resources

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The rate of O₂loss from mesenteric arterioles is not unusually high