| 1. |
- Axelsson, Josefin, et al.
(författare)
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Acute hyperglycemia induces rapid, reversible increases of glomerular permeability in non-diabetic rats.
- 2010
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Ingår i: American Journal of Physiology-Renal Physiology. - : American Physiological Society. - 1522-1466 .- 1931-857X. ; 298:6, s. 1306-1312
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Tidskriftsartikel (refereegranskat)abstract
- This study was performed to investigate the impact of acute hyperglycemia (HG) on the permeability of the normal glomerular filtration barrier in vivo. In anaesthetized Wistar rats (250-280g), the left ureter was catheterized for urine collection, while simultaneously blood access was achieved. Rats received an intravenous (i.v.) infusion of either 1) hypertonic glucose to maintain blood glucose at 20-25 mM (G; n=8); 2) hypertonic glucose as in 1) and a Rho-A-kinase inhibitor (Y-27632; Rho-G; n=8); 3) 20% mannitol (MANN; n=7), or 4) hypertonic (12%) NaCl to maintain plasma crystalloid osmotic pressure (picry) at ~320-325 mOsm/l (NaCl; n=8); 5) physiologic saline (SHAM; n=8). Fluorescein isothiocyanate (FITC)-Ficoll 70/400 was infused i.v. for at least 20 min before terminating the experiments, and plasma and urine collected to determine the glomerular sieving coefficients () for polydisperse Ficoll (mol. radius 15-80A) by high performance size exclusion chromatography. In G there was a marked increase in for Ficoll55-80A at 20 min, which was completely reversible within 60 min and abrogated by a Rho-kinase (ROCK) inhibitor, while glomerular permeability remained unchanged in MANN and NaCl. In conclusion, acute HG caused rapid, reversible increases in for large Ficolls, not related to the concomitant hyperosmolarity, but sensitive to ROCK inhibition. The changes observed were consistent with the formation of an increased number of large pores in the glomerular filter. The sensitivity of the permeability changes to ROCK inhibition strongly indicates that the cytoskeleton of the cells in the glomerular barrier be involved in these alterations. Key words: microalbuminuria, Rho-A-kinase, podocytes, endothelium.
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| 2. |
- Axelsson, Josefin, et al.
(författare)
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Rapid, dynamic changes in glomerular permeability to macromolecules during systemic Angiotensin II (AngII) infusion in rats.
- 2012
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Ingår i: American Journal of Physiology-Renal Physiology. - : American Physiological Society. - 1522-1466 .- 1931-857X. ; 303:6, s. 790-799
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Tidskriftsartikel (refereegranskat)abstract
- The actions of systemic angiotensin II (AngII) infusions on glomerular permeability were investigated in vivo. In anaesthetized Wistar rats (250-280g) the left ureter was cannulated for urine collection, while simultaneously blood access was achieved. Rats were continuously infused i.v. with either of four doses of AngII (16 ng/kg/min (Lo-AngII; n=7), 230 ng/kg/min (Lo-Int-AngII; n=8), 910 ng/kg/min (Hi-Int-AngII; n=7), or 1.82 μg/kg/min (Hi-AngII; n=8)), or with the calcium channel blocker, nimodipine, together with the Hi-Int-AngII dose (n=6), respectively, and with polydisperse fluorescein isothiocyanate (FITC)-Ficoll-70/400 (mol.radius 10-80Å) and (51)Cr-EDTA. Plasma and urine samples were taken at 5, 15, 30, 60 and 120 min and analyzed by high performance size exclusion chromatography (HPSEC) for determination of glomerular sieving coefficients (θ) to Ficoll. Mean arterial pressure (MAP) and glomerular filtration rate (GFR) were also assessed. In AngII groups there was a rapid, marked increase in glomerular permeability (θ) to Ficoll molecules >34Å, which was completely abrogated by the AngII-blocker, candesartan. The permeability increase was reversible within 15-60 min, but some increases remained even after 60 min. For the highest AngII doses given GFR decreased transiently, concomitant with marked increases in MAP. Nimodipine blocked the hemodynamic AngII actions, whereas the glomerular permeability response remained unchanged. According to a two-pore model and a log-normal distributed pore model the AngII induced increases in glomerular permeability are compatible with an increased number of "large pores" in the glomerular filter, and, to some extent, an increase in the dispersity of the small pore radius.
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| 3. |
- Axelsson, Josefin, et al.
(författare)
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Reduced diffusion of charge-modified, conformationally intact anionic Ficoll relative to neutral Ficoll across the rat glomerular filtration barrier in vivo
- 2011
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Ingår i: American Journal of Physiology-Renal Physiology. - : American Physiological Society. - 1522-1466 .- 1931-857X. ; 301:4, s. 708-712
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Tidskriftsartikel (refereegranskat)abstract
- Axelsson J, Sverrisson K, Rippe A, Fissell W, Rippe B. Reduced diffusion of charge-modified, conformationally intact anionic Ficoll relative to neutral Ficoll across the rat glomerular filtration barrier in vivo. Am J Physiol Renal Physiol 301: F708-F712, 2011. First published July 20, 2011; doi:10.1152/ajprenal.00183.2011.-The glomerular filtration barrier (GFB) is commonly conceived as a negatively charged sieve to proteins. Recent studies, however, indicate that glomerular charge effects are small for anionic, carboxymethylated (CM) dextran vs. neutral dextran. Furthermore, two studies assessing the glomerular sieving coefficients (theta) for negative CM-Ficoll vs. native Ficoll have demonstrated an increased glomerular permeability for CM-Ficoll (Asgeirsson D, Venturoli D, Rippe B, Rippe C. Am J Physiol Renal Physiol 291: F1083-F1089, 2006; Guimaraes M, Nikolovski J, Pratt L, Greive K, Comper W. Am Physiol Renal Physiol 285: F1118-F1124, 2003.). The CM-Ficoll used, however, showed a larger Stokes-Einstein radius (a(e)) than neutral Ficoll, and it was proposed that the introduction of negative charges in the Ficoll molecule had made it more flexible and permeable. Recently, a negative FITC-labeled CM-Ficoll (CMI-Ficoll) was produced with a conformation identical to that of neutral FITC-Ficoll. Using these probes, we determined their theta:s in anesthetized Wistar rats (259 +/- 2.5 g). After blood access had been achieved, the left ureter was cannulated for urine sampling. Either polysaccharide was infused (iv) together with a filtration marker, and urine and plasma were collected. Assessment of theta FITC-Ficoll was achieved by high-performance size-exclusion chromatography (HPSEC). CMI-Ficoll and native Ficoll had identical elugrams on the HPSEC. Diffusion of anionic Ficoll was significantly reduced compared with that of neutral Ficoll across the GFB for molecules of a(e) similar to 20-35 angstrom, while there were no charge effects for Ficoll of a(e) similar to 35-80 angstrom. The data are consistent with a charge effect present in "small pores," but not in "large pores," of the GFB and mimicked those obtained for anionic membranes in vitro for the same probes.
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| 4. |
- Axelsson, Josefin, et al.
(författare)
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Scavengers of reactive oxygen species, paracalcitol, RhoA and Rac-1 inhibitors and tacrolimus inhibit angiotensin II induced actions on glomerular permeability.
- 2013
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Ingår i: American Journal of Physiology-Renal Physiology. - : American Physiological Society. - 1522-1466 .- 1931-857X. ; 305:3, s. 237-243
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Tidskriftsartikel (refereegranskat)abstract
- Systemic infusions of angiotensin II (AngII) rapidly induce large, dynamic increases in the permeability of the glomerular filtration barrier (GFB) in rats. After binding to its receptor(s), AngII generates reactive oxygen species (ROS) and produces Ca(2+) influx into cells, leading to activation of a plethora of signaling cascades, including e.g. calcineurin, and small GTPases, such as Rac-1 and RhoA. In the present study we sought to interact with some of these cascades in order to test potential novel antiproteinuric agents. In anaesthetized Wistar rats the left urether was cannulated for urine collection, and blood access was achieved. Rats were infused with AngII (16 ng/kg/min) alone, or together with the ROS scavengers, TEMPOL or dimethylthiourea (DMTU), or the D-vitamin analog, paracalcitol, the RhoA-kinase inhibitor, Y-27632, the Rac-1 inhibitor, NSC-23766, or the calcineurin inhibitor, tacrolimus. FITC-Ficoll-70/400 (mol.radius 10-80Å) and (51)Cr-EDTA were infused throughout the experiment. Plasma and urine samples were taken during baseline and at 5 and 15 min after the start of the infusions and analyzed by high performance size exclusion chromatography (HPSEC) for determination of glomerular sieving coefficients (θ) for Ficoll10-80Å. AngII infusion into rats caused marked increases in glomerular permeability to large Ficoll molecules (Ficoll50-80Å), which were abrogated by the ROS scavenger TEMPOL and partly by DMTU. Paracalcitol, RhoA and Rac-1 inhibition, and, to some extent, tacrolimus, but not prostacyclin, could also inhibit the glomerular permeability actions of AngII. Our data suggest that cellular ROS generation and active Ca(2+) signaling are involved in AngII induced increases in glomerular permeability.
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| 5. |
- Axelsson, Josefin, et al.
(författare)
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Size-selectivity of a synthetic high-flux and a high cut-off dialyzing membrane compared to that of the rat glomerular filtration barrier
- 2012
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Ingår i: Journal of Membrane Science. - : Elsevier BV. - 0376-7388. ; 413, s. 29-37
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate the size-selectivity of two different synthetic dialyzing membranes, having widely differing sieving properties, with respect to their handling of polydispersed fluorescein isothiocyanate (FITC)-Ficoll, FITC-dextran and of proteins, i.e. I-125-human serum albumin (RISA) and I-125-myoglobin (Myo). Are Ficoll and dextran, compared to proteins, "hyperpermeable" across synthetic dialyzing membranes, similar to their behavior across the glomerular filtration barrier (GFB)? A high-flux membrane (HF-Revaclear (R); n = 12) and a high cut-off membrane (HCO; n = 14) in capillary mini-dialyzers were perfused with diluted horse serum. The perfusate contained polydisperse FITC-Ficoll 70/400 or FITC-dextran (mol radius 13-80 angstrom), FITC-Inulin, and, in some experiments, RISA/Myo. After a priming period, sampling of filtrate occurred, and a midpoint plasma sample taken. Filtrate-to-plasma concentration ratios (theta) vs. molecular radius (a(e)) were assessed using HPLC for Ficoll and dextran. Size-selectivity for Ficoll increased in the order: HF-Revaclear (R) < rat glomerulus < HCO. Although the HCO filter showed the highest cut-off, this occurred at the expense of a high permeability to albumin and large Ficoll molecules and a high degree of dispersity of (small) pore radii, as assessed using a log-normal + shunt distributed pore model. According to a two-pore model, the fractional hydraulic conductance accounted for by large pores (alpha(L)) was 8.58 +/- 0.93 x 10(-3) and 1.51 +/- 0.88 x 10(-3) for the HCO and the HF-Revaclear (R), respectively, compared to 4.1 +/- 0.80 x 10(-5) for the rat glomerulus. In conclusion, the HCO filter investigated showed a high theta for myoglobin, similar to that of the GFB. However, the number of large pores was markedly higher and the pore size heterogeneity markedly larger than for the GFB. Membrane permeability was dependent on molecular species and increased in the order: proteins < Ficoll < dextran. (C) 2012 Published by Elsevier B.V.
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| 6. |
- Axelsson, Josefin, et al.
(författare)
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Transient and sustained increases in glomerular permeability following ANP infusion in rats.
- 2011
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Ingår i: American Journal of Physiology-Renal Physiology. - : American Physiological Society. - 1522-1466 .- 1931-857X. ; 300, s. 24-30
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Tidskriftsartikel (refereegranskat)abstract
- The present study was performed to investigate the effects of systemic atrial natriuretic peptide (ANP) infusion on the glomerular permeability to macromolecules in rats. In anaesthetized Wistar rats (250-280g) the left urether was cannulated for urine collection while simultaneously blood access was achieved. Rats were continuously infused i.v. with ANP, 30 ng/min/kg (Lo-ANP; n=8) or 800 ng/min/kg (Hi-ANP; n=10) or 0.9% NaCl (SHAM; n=16), respectively, and with polydisperse fluorescein isothiocyanate (FITC)-Ficoll-70/400 (mol.radius 13-90Å) and (51)Cr-EDTA for 2 h. Plasma and urine samples were taken at 5, 15, 30, 60 and 120 min of ANP infusion, and analyzed by high performance size exclusion chromatography (HPLC) for determination of glomerular sieving coefficients () for Ficoll. GFR was also assessed ((51)Cr-EDTA). In Hi-ANP there was a rapid (within 5 min), but bimodal, increase in glomerular permeability. to high MW Ficoll thus reached a maximum at 15 min, after which returned to near control at 30 min, to again increase moderately at 60 and 120 min. In Lo-ANP there was also a rapid, reversible increase in glomerular , returning to near control at 30 min, followed by just a tendency of a sustained increase in permeability, but with a significant increase in "large pore" radius. In conclusion, in Hi-ANP there was a rapid increase in glomerular permeability, with an early, partly reversible permeability peak, followed by a (moderate) sustained increase in permeability. In Lo-ANP animals, only the initial permeability peak was evident. In both Lo-ANP and Hi-ANP the glomerular sieving pattern observed was found to mainly reflect an increase in the number and radius of "large pores" in the glomerular filter.
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| 7. |
- Sverrisson, Kristinn, et al.
(författare)
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Dynamic, size-selective effects of protamine sulfate and hyaluronidase on the rat glomerular filtration barrier in vivo.
- 2014
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Ingår i: American Journal of Physiology-Renal Physiology. - : American Physiological Society. - 1522-1466 .- 1931-857X. ; 307:10, s. 1136-1143
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Tidskriftsartikel (refereegranskat)abstract
- The proteinuric actions of protamine sulfate (PS) have classically been, at least partly, attributed to alterations of the negatively charged glomerular endothelial glycocalyx (GC). To investigate whether the charge-selective properties of the glomerular filtration barrier (GFB) would be altered by PS we assessed the glomerular sieving of conventional, uncharged, polydispersed Ficoll (n-Ficoll) compared to charge modified, conformationally intact, anionic (carboxymethylated) Ficoll (a-Ficoll) before and after systemic infusions of PS in rats. For comparison we also investigated the impact of hyaluronidase (Hyase), which partially degrades the GC, on GFB permeability. In anaesthetized Wistar rats blood access was achieved and the left ureter was cannulated for urine collection. Rats were infused with either n-Ficoll or a-Ficoll before and during systemic infusions with either PS or Hyase. Plasma and urine samples were taken repeatedly and analyzed by high performance size exclusion chromatography (HPSEC) for assessing glomerular sieving coefficients (θ) for Ficoll (radius 10-80Å). The GFB showed a significant glomerular charge selectivity for Ficoll molecules of radius 20-35Å (Ficoll20-35Å). PS and Hyase infusions reversibly increased θ for large Ficoll molecules (Ficoll50-80Å). Thus, for PS θ for a-Ficoll70Å increased from 2.47 x 10(-5) ± 1.1(-5) to 7.25 x 10(-5) ± 1.1(-5) (P<0.05) at 15 min. For Hyase the changes in a-Ficoll50-80Å were, however, not statistically significant. Neither PS nor Hyase had any effect on θ for n-Ficoll20-45Å or a-Ficoll20-45Å. It is concluded that systemically administered PS and Hyase in moderate doses dynamically decreased the size-selectivity of the rat GFB without affecting its charge selective properties.
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| 8. |
- Sverrisson, Kristinn, et al.
(författare)
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Extracellular fetal hemoglobin induces increases in glomerular permeability: inhibition with alfa-1-microglobulin and tempol
- 2014
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Ingår i: American Journal of Physiology-Renal Physiology. - : American Physiological Society. - 1522-1466 .- 1931-857X. ; 306:4, s. 442-448
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular fetal hemoglobin (HbF) and adult hemoglobin (HbA) are proinflammatory and generate ROS. Increased plasma levels of extracellular HbF have recently been reported to occur in early preeclampsia. α1-Microglobulin (A1M) is a physiological heme-binding protein and radical scavenger that has been shown to counteract vascular permeability increases induced by HbA in the perfused placenta. The present study was performed to investigate whether HbF and HbA will increase glomerular permeability in vivo and to test whether A1M and tempol, a ROS scavenger, can prevent their effects. Anesthetized Wistar rats were continuously infused intravenously with either HbA, HbF, or cyano-inactivated HbF together with FITC-Ficoll-70/400, inulin, and51Cr-labeled EDTA for 2 h. Plasma samples and urine samples (left ureter) were taken repeatedly and analyzed by high-performance size exclusion chromatography to assess glomerular sieving coefficients for Ficoll of radius 10–80 Å. In separate experiments, A1M or tempol was given before and during Hb infusions. Extracellular HbF caused rapid, transient increases in glomerular permeability to large Ficoll molecules (50–80Å), contrary to the effects of HbA and cyano-inactivated HbF. For HbF, glomerular sieving coefficients for Ficoll of radius 60Å increased from 3.85 ± 0.85 × 10−5to 2.60 ± 0.96 × 10−4at 15 min, changes that were abrogated by tempol and reduced by A1M. In conclusion, our data demonstrate that extracellular HbF, infused systemically, can acutely increase glomerular permeability through inducing oxidative stress.
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