Distribution of Radioisotope-Labeled Microparticles in the Renal Cortex of Dogs in Hemorrhagic Hypotension

Ofstad, J.; Willassen, Yngvar; Egenberg, Karl Edvard

doi:10.3109/00365517309082432

Cited by 11 publications

(5 citation statements)

References 19 publications

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“…When comparing zonal flow estimated from diffusible tracers versus microsphere uptake, one should keep in mind the different ways of uptake. While practically all Ms (15 pm) are arrested in afferent arterioles or glomeruli (McNay & Abe 1970, Ofstad, Willassen & Egenberg 1973 and therefore reflect glomerular blood flow, the diffusible tracers are probably delivered mainly by the postglomerular peritubular capillaries. Thus the low Ms uptake in the medulla is a simple consequence of the absence of glomeruli in this region.…”

Section: Flow Distribution Within Each Zonementioning

confidence: 99%

Distribution of blood flow in the dog kidney: I. Saturation rates for inert diffusible tracers, ¹²⁵I‐iodoantipyrine and tritiated water, versus uptake of microspheres under control conditions

Clausen

Hope

Kirkebø

et al. 1979

Acta Physiologica Scandinavica

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Disparate reports on intrarenal blood flow distribution prompted a direct comparison between microspheres (Ms) and inert diffusible tracers (DT). The "tissue sampling technique" for estimating local flow with DT (Kety) was adapted for the dog kidney, using 125I-iodoantipyrine (1-Ap) and tritiated water (THO). Ms (15 micron) were injected 2-3 min prior to 10-15 s DT infusion made during continuous 1 s arterial blood sampling. Tracers were measured in 7 to 20 samples from each of the following zones: Outer, middle and inner cortex (C1, C2, C3), outer and inner halves of outer medulla (OM1, OM2), and inner medulla (IM). I-Ap and THO gave closely similar flow distribution, and average total renal blood flow (RBF) of 3.90 and 3.78 as compared to 3.94 ml/min . g with Ms. Flow in C2 (ml/min . g) was similar with all tracers, and in per cent thereof average local flows were: C1 102, C3 70, OM1 34, OM2 12, and IM 2 with DT versus 117, 53, 12, 3, and 0 with Ms. Zonal flow fractions of total RBF obtained with DT were: C1 0.41, C2 0.33, and C3+medulla 0.26 versus 0.51, 0.33 and 0.16 with Ms. Thus, a Ms surplus in C1 relative to DT flow, representing 10% of total RBF, matched a Ms deficit in C3+medulla. This disparity might result from: (1) Failure of Ms to enter deep afferent arterioles in proportion to blood flow, (2) diffusion of DT from deep portions of the interlobular arteries, and/or (3) postglomerular inward flow of blood and DT.

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Section: Flow Distribution Within Each Zonementioning

confidence: 99%

Distribution of blood flow in the dog kidney: I. Saturation rates for inert diffusible tracers, ¹²⁵I‐iodoantipyrine and tritiated water, versus uptake of microspheres under control conditions

Clausen

Hope

Kirkebø

et al. 1979

Acta Physiologica Scandinavica

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“…The mean afferent arteriolar diameter of 20 jum in the rat is fairly close to the value recently obtained by Morkrid et al (1978) in the dog. We believe that measurement of afferent arteriolar diameter using this microsphere method is a sensitive technique, as it has been shown to detect changes in diameter of the afferent arterioles in hemorrhagic hypotension (Ofstad et al, 1973), following a decrease in renal arterial pressure by aortic clamp (Morkrid et al, 1978), and in acute renal failure induced by intramuscular injection of glycerol (Hsu et al, 1979). The preponderance of recent evidence has indicated that the efferent vasculature is the primary site of action of angiotensin II.…”

Section: Discussionmentioning

confidence: 97%

Effect of exogenous angiotensin II on renal hemodynamics in the awake rat. Measurement of afferent arteriolar diameter by the microsphere method.

Hsu¹,

Kurtz²,

Slavicek³

1980

Circulation Research

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We measured cardiac output (CO), renal blood flow (RBF), renal plasma flow (RPF), and afferent arteriolar diameter by the microsphere method, and inulin clearance (GFR) simultaneously in awake rats given an infusion of exogenous angiotensin II (100 ng/min per kg). Angiotensin II did not affect the CO, whereas both RBF and RPF decreased significantly in rats infused with angiotensin II (RBF, 2.88 +/- 0.11, mean +/- SE; RPF, 1.78 +/- 0.09, n = 6) when compared to control animals given saline (RBF, 4.58 +/- 0.31; RPF, 2.80 +/- 0.24 ml/min per 100 g, n = 6, both P less than 0.005, respectively). Both mean arterial pressure (MAP) and renal vascular resistance (RVR) were significantly higher in rats infused with antiogensin II than in controls. The decrease in GFR did not parallel the reduction of RPF in rats infused with angiotensin II as reflected by their higher values of mean filtration fraction (41.1 +/- 1.6%, n = 6) than that of controls (33.7 +/- 2.4%, n = 6, P less than 0.05). Despite significant elevations of MAP and RVR in rats infused with angiotensin II, their mean afferent arteriolar diameter (19.6 +/- 0.24 micron) was not different from that of controls (20.1 +/- 0.39 micron). We conclude that angiotensin II preferentially acts at the site of postglomerular vasculature but not at the afferent arteriole.

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“…The radioactivity of the isotopes in the different cortical layers also was recorded; details of the methods have been described earlier. 4 The percent of spheres with diameters greater than 20 ^m recovered in the juxtamedullary cortex was significantly lower than for spheres of smaller size (Table I). The percent reduction of spheres recovered in the juxtamedullary cortex seemed to occur when the sphere diameter exceeded 17 ^m (Fig.…”

Section: Observations Of the Distribution Of Spheres In Differentmentioning

confidence: 90%

“…4 Six kidneys from three anesthetized, fully grown, normotensive mongrel dogs weighing 13-16 kg, in which microspheres with diameters ranging from 10 to 35 ^m were injected through the thoracic aorta, were studied by microscopic analysis of 35-^m-thick sections. The diameters of the spheres and their position in three cortical layers of equal thickness (outer, middle, and juxtamedullary cortex) were recorded.…”

Section: Observations Of the Distribution Of Spheres In Differentmentioning

confidence: 99%

Effect of steric restriction on the intracortical distribution of microspheres in the dog kidney.

Mørkrid¹,

Ofstad²,

Willassen³

1976

Circulation Research

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The effect on the intracortical distribution of microspheres and radioactivity caused by steric hindrance of the free movement of spheres into afferent arterioles are described by two mathematical models. The results are compared with corresponding experimental data obtained in six kidneys from normotensive dogs. The first model (A) assumes that spheres are distributed as blood flow, regardless of their size, except for those having diameters greater than that of an afferent arteriole and which do not enter this vessel. The second model (B) includes the Ferry correction. The experimental data show that the percent recovery of spheres with diameters of 20-25 mum was significantly greater in the outer cortex and significantly less in the juxtamedullary cortex than recovery of the smaller spheres, and that the distribution of spheres with diameters of 10 mum to about 17 mum seems uninfluenced by the sphere size. The experimental results we have obtained fit best with model A. We found that according to both models steric restriction is a factor of major importance in relation to the intracortical distribution of spheres, and the analysis shows that the blood flow in the inner part of the renal cortex is grossly underestimated by the method of isotope labeled microspheres when diameters of 15 +/- 5 mum are used in the dog. Furthermore we found that dilation of the afferent arterioles will change the steric hindrance so that a redistribution of spheres and radioactivity may occur without any redistribution of blood flow. It is suggested that the results interpreted as redistribution of blood flow can be explained as due to altered steric hindrance alone, i.e., as a methodological artifact.

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Distribution of Radioisotope-Labeled Microparticles in the Renal Cortex of Dogs in Hemorrhagic Hypotension

Cited by 11 publications

References 19 publications

Distribution of blood flow in the dog kidney: I. Saturation rates for inert diffusible tracers, ¹²⁵I‐iodoantipyrine and tritiated water, versus uptake of microspheres under control conditions

Distribution of blood flow in the dog kidney: I. Saturation rates for inert diffusible tracers, ¹²⁵I‐iodoantipyrine and tritiated water, versus uptake of microspheres under control conditions

Effect of exogenous angiotensin II on renal hemodynamics in the awake rat. Measurement of afferent arteriolar diameter by the microsphere method.

Effect of steric restriction on the intracortical distribution of microspheres in the dog kidney.

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Distribution of Radioisotope-Labeled Microparticles in the Renal Cortex of Dogs in Hemorrhagic Hypotension

Cited by 11 publications

References 19 publications

Distribution of blood flow in the dog kidney: I. Saturation rates for inert diffusible tracers, 125I‐iodoantipyrine and tritiated water, versus uptake of microspheres under control conditions

Distribution of blood flow in the dog kidney: I. Saturation rates for inert diffusible tracers, 125I‐iodoantipyrine and tritiated water, versus uptake of microspheres under control conditions

Effect of exogenous angiotensin II on renal hemodynamics in the awake rat. Measurement of afferent arteriolar diameter by the microsphere method.

Effect of steric restriction on the intracortical distribution of microspheres in the dog kidney.

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Distribution of blood flow in the dog kidney: I. Saturation rates for inert diffusible tracers, ¹²⁵I‐iodoantipyrine and tritiated water, versus uptake of microspheres under control conditions

Distribution of blood flow in the dog kidney: I. Saturation rates for inert diffusible tracers, ¹²⁵I‐iodoantipyrine and tritiated water, versus uptake of microspheres under control conditions