| 1. |
- Albinsson, Sebastian, et al.
(författare)
-
Arterial remodeling and plasma volume expansion in caveolin-1 deficient mice.
- 2007
-
Ingår i: American Journal of Physiology: Regulatory, Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 293, s. 1222-1231
-
Tidskriftsartikel (refereegranskat)abstract
- Caveolin- 1 ( Cav- 1) is essential for the morphology of membrane caveolae and exerts a negative influence on a number of signaling systems, including nitric oxide ( NO) production and activity of the MAP kinase cascade. In the vascular system, ablation of caveolin- 1 may thus be expected to cause arterial dilatation and increased vessel wall mass ( remodeling). This was tested in Cav- 1 knockout ( KO) mice by a detailed morphometric and functional analysis of mesenteric resistance arteries, shown to lack caveolae. Quantitative morphometry revealed increased media thickness and media- to- lumen ratio in KO. Pressure- induced myogenic tone and flow- induced dilatation were decreased in KO arteries, but both were increased toward wild- type ( WT) levels following NO synthase ( NOS) inhibition. Isometric force recordings following NOS inhibition showed rightward shifts of passive and active length- force relationships in KO, and the force response to alpha 1- adrenergic stimulation was increased. In contrast, media thickness and force response of the aorta were unaltered in KO vs. WT, whereas lumen diameter was increased. Mean arterial blood pressure during isoflurane anesthesia was not different in KO vs. WT, but greater fluctuation in blood pressure over time was noted. Following NOS inhibition, fluctuations disappeared and pressure increased twice as much in KO ( 38 +/- 6%) compared with WT ( 17 +/- 3%). Tracer- dilution experiments showed increased plasma volume in KO. We conclude that NO affects blood pressure more in Cav- 1 KO than in WT mice and that restructuring of resistance vessels and an increased responsiveness to adrenergic stimulation compensate for a decreased tone in Cav- 1 KO mice.
|
|
| 2. |
- Grände, Gustaf, et al.
(författare)
-
Unaltered Size-selectivity of the Glomerular Filtration Barrier in Caveolin-1 Knock-out (KO) mice.
- 2009
-
Ingår i: American Journal of Physiology: Renal, Fluid and Electrolyte Physiology. - : American Physiological Society. - 0363-6127. ; 297:2, s. 257-262
-
Tidskriftsartikel (refereegranskat)abstract
- The transfer of albumin from blood to tissue has been found to be increased in caveolin-1 knock-out (KO) mice. This has been considered to reflect an increased microvascular permeability, conceivably caused by an increased endothelial production of nitric oxide (NO) in mice lacking caveolin-1. To investigate whether such an increase in endothelial NO-production would also affect the glomerular barrier characteristics, the glomerular sieving coefficients () to neutral, polydisperse fluorescein isothiocyanate (FITC)-Ficoll 70/400 (mol. radius 15-90 A) were determined in caveolin-1 KO mice vs. their wild-type counterparts. for Ficoll were assessed using high performance size exclusion chromatography (HPSEC) on blood and urine samples. Furthermore, the transcapillary escape rate (TER) of (125)I-labeled albumin and plasma volume (PV) were determined in both types of mice. Despite an increase in the glomerular filtration rate (GFR) in caveolin-1 KO mice (0.23+/-0.04 mL/min; n=7 vs. 0.10+/-0.02 mL/min; n=7; p<0.05) the glomerular Ficoll sieving curves were nearly identical. Furthermore, caveolin-1 KO mice showed an increased PV (6.59+/-0.42 mL/100g vs. 5.18+/-0.13 mL/100g; p<0.01) but only a tendency of an increased TER (14.69+/-1.59 %/h vs. 11.62+/-1.62 %/h; N.S.). It is concluded that in caveolin-1 KO mice the glomerular permeability was not increased, despite the presence of glomerular hyperfiltration. The present data are in line with the concept that the increased transvascular albumin leakage previously found in mice lacking caveolin-1 may be due to an elevation in systemic microvascular pressure following NO-induced precapillary vasodilatation, rather than being a consequence of an increased microvascular permeability per se. Key words: capillary permeability, nitric oxide, sieving coefficient, Ficoll, glomerular filtration rate.
|
|
| 3. |
- Rippe, Anna, et al.
(författare)
-
Disproportionally low clearance of macromolecules from the plasma to the peritoneal cavity in a mouse model of peritoneal dialysis (PD).
- 2007
-
Ingår i: Nephrology Dialysis Transplantation. - : Oxford University Press (OUP). - 1460-2385 .- 0931-0509. ; 22:1, s. 88-95
-
Tidskriftsartikel (refereegranskat)abstract
- Background. This study was performed to establish a model for quantitative measurements of a number of basic peritoneal transport parameters, particularly transperitoneal clearances (Cl) of macromolecules, during mouse peritoneal dialysis. Methods. Mice were anaesthetized using 3% isofluorane inhalation anaesthesia. The right jugular vein and the left femoral artery were cannulated for infusion and sampling purposes and for registration of (mean) arterial blood pressure. Access to the peritoneal cavity occurred via a thin abdominal catheter (Ø 0.7 mm). About 2.5 ml of either 4% (n = 9) or 1.5% (n = 5) glucose containing PD-fluid were instilled intraperitoneally (i.p.). Dialysate volume was followed vs time using i.p. RISA (125I human serum albumin) as a volume marker, after correcting for RISA mass disappearance from the peritoneum, assessed separately (n = 11). Microsampling (10 µl) of plasma and dialysate was performed for determinations of glucose, haematocrit, radioactivity (RISA and 51Cr-EDTA) and Ficoll. Results. The i.p. volume vs time curves [VD(t)] were, after scaling, similar to those observed in humans (and in rats). Clearance of RISA out of the peritoneal cavity (Clout) was 9.33 ± 0.83 µl/min and the clearance of RISA to plasma (Cl->P) and the RISA clearance to the peritoneal cavity (Cl->D) were 1.49 ± 0.13 and 0.084 ± 0.008 µl/min, respectively. The peritoneal transport coefficients for 51Cr-EDTA and glucose, as well as Clout and Cl->P, were 13–17% of those previously assessed in 300 g rats, whereas Cl->D was only ~2% of that in rat. Conclusions. All peritoneal transport parameters measured, except Cl->D, scaled very well to the corresponding human data. The mechanisms of the disproportionally low clearance of macromolecules from the plasma to the peritoneal cavity in mice remain elusive and warrant further study.
|
|
| 4. |
- Rippe, Catarina, et al.
(författare)
-
Effects of glomerular filtration rate on Ficoll sieving coefficients (theta) in rats.
- 2006
-
Ingår i: Kidney International. - : Elsevier BV. - 1523-1755 .- 0085-2538. ; 69:8, s. 1326-1332
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to assess the role of diffusion and convection during filtration of Ficoll across the glomerular filter by comparing glomerular sieving coefficients ( h) to neutral fluorescein isothiocyanate ( FITC)-Ficoll 70/400 obtained at low ( hydropenic) vs raised ( normal) glomerular filtration rates (GFRs). The h for FITC-Ficoll was determined in anesthetized Wistar rats (304 +/- 18 g) following laparotomy and cannulation of the ureters, used for urine sampling. After surgery, GFR was 1.2 +/- 0.16 ml/ min (+/- s. e.), assessed using the plasma to urine clearance of FITC-inulin and Cr-51-ethylenediaminetetraacetic acid. FITC-Ficoll 70/400 was infused intravenously (i.v.) following an initial bolus dose. To raise GFR, to an average of similar to 2 ml/ min, 5 ml of serum together with glucagon ( 3 mu g/min) was given i.v. FITC- inulin and FITC- Ficoll were determined in plasma and urine using size-exclusion high-performance liquid chromatography. The h for Ficoll as a function of Stokes - Einstein radius was significantly reduced in the range of 13 - 43 angstrom when GFR was raised. The maximal h lowering effect, in relative terms, of raising GFR was obtained for a Ficoll a(e) of similar to 32 angstrom. For Ficoll(36 angstrom) (cf. albumin), h was reduced from 0.111 +/- 0.009 to 0.081 +/- 0.012 ( P<0.05; n = 7) for the GFR increment imposed. The reduction in h for Ficoll after raising GFR indicates the presence of a high diffusive component of glomerular Ficoll filtration in rats in vivo and contradicts the notion of a significant concentration polarization effect in the glomerular filter upon Ficoll molecules <50 angstrom in radius.
|
|
| 5. |
- Rippe, Catarina, et al.
(författare)
-
Nature of glomerular capillary permeability changes following acute renal ischemia/reperfusion (I/R) injury in rats.
- 2006
-
Ingår i: American Journal of Physiology: Renal, Fluid and Electrolyte Physiology. - : American Physiological Society. - 0363-6127. ; 291:6, s. 1362-1368
-
Tidskriftsartikel (refereegranskat)abstract
- This study was performed to evaluate the alterations of glomerular filtration barrier characteristics following acute renal ischemia-reperfusion (I/R). Ischemia was induced in anesthetized rats by unilateral renal artery occlusion for either 20 or 60 min, followed by reperfusion during 20 or 60 min, respectively, with the contralateral kidney serving as control. Sieving coefficients (theta) were obtained by analyzing Ficoll [mol.radius (a(e)) 13-85 angstrom] in urine and plasma after 20 and 60 min I/R. Furthermore, theta for human serum albumin (HSA) was estimated using a tissue uptake technique after 20 and 60 min of I/R, while clearance of HSA compared with that for neutralized HSA (nHSA) was assessed after 20 min of I/R only. Glomerular filtration rate (GFR) was measured by [Cr-51] EDTA and inulin. I/R reduced GFR and increased theta for Ficoll molecules of a(e) > 55 angstrom and theta for albumin. theta for Ficoll vs. a(e), analysed using a two-pore model, demonstrated that, despite increases in theta, the large-pore fractional ultrafiltration coefficient (alpha(L)) was unchanged after 20 min of I/R, owing to the decline in GFR, but increased after 60 min of I/R. However, the apparent alpha(L) for albumin increased already after 20 min of I/R (P < 0.005) and the nHSA/HSA clearance ratio was slightly reduced, possibly reflecting a diminished negative charge barrier. In conclusion, after 20 min of I/R, indications of a reduced charge selectivity were noted, while after 60 min of I/R, there was mainly a reduction in size selectivity, compatible with an increased formation of large pores.
|
|
| 6. |
- Rippe, Catarina, et al.
(författare)
-
Size and charge selectivity of the glomerular filter in early experimental diabetes in rats
- 2007
-
Ingår i: American Journal of Physiology: Renal, Fluid and Electrolyte Physiology. - : American Physiological Society. - 0363-6127. ; 293:5, s. 1533-1538
-
Tidskriftsartikel (refereegranskat)abstract
- Microalbuminuria is an early sign of diabetic nephropathy. The aim of the present study was to investigate whether the changes of the glomerular filtration barrier in early experimental diabetes are due to size- or charge-selective alterations. Wistar rats, made diabetic by streptozotocin (STZ) and having their blood glucose maintained at similar to 20 mM for 3 or 9 wk, were compared with age-matched controls. Glomerular clearances of native albumin (C1-HSA) and neutralized albumin (C1-nHSA) were assessed using a renal uptake technique. Glomerular filtration rate and renal plasma flow were assessed using Cr-51-EDTA and [ I-125]iodohippurate, respectively. In a separate set of animals, diabetic for 9 wk, and in controls, glomerular sieving coefficients (theta) for neutral FITC-Ficoll (molecular radius: 15-90 angstrom) were assessed using size exclusion chromatography. At 3 wk of diabetes, C1-HSA and C1-nHSA remained unchanged, indicating no alteration in either size or charge selectivity. By contrast, at 9 wk of diabetes, there was a twofold increase of C1-HSA, whereas C1-nHSA remained largely unchanged, at first suggesting a glomerular charge defect. However, according to a two-pore model, the number of large pores, assessed from both Ficoll and C1-HSA, increased twofold. In addition, a small reduction in proximal tubular reabsorption was observed at 3 wk, which was further reduced at 9 wk. In conclusion, no functional changes were observed in the glomerular filtration barrier at 3 wk of STZ-induced diabetes, whereas at 9 wk there was a decrease in size selectivity due to an increased number of large glomerular pores.
|
|
| 7. |
- Rosengren, Bert-Inge, et al.
(författare)
-
Transvascular protein transport in mice lacking endothelial caveolae.
- 2006
-
Ingår i: American Journal of Physiology: Heart and Circulatory Physiology. - : American Physiological Society. - 1522-1539 .- 0363-6135. ; 291:3, s. 1371-1377
-
Tidskriftsartikel (refereegranskat)abstract
- Caveolae are Omega-shaped vesicular structures postulated to play a role in transvascular protein transport. Studies on mice lacking endothelial caveolae, caveolin-1 knockout (Cav-1-KO) mice, indicate increased macromolecular transport rates. This was postulated to be due to the appearance of an alternative pathway. The present study tested whether an alternative pathway had appeared in Cav-1-KO mice. Male Cav-1-KO (n=12) and male control mice (n=13) were intubated and anesthetized using 2% isoflurane. I-125-labeled albumin, I-131-labeled immunoglobulin M (IgM), and polydisperse FITC-Ficoll were administered intravenously. During tracer administration, a 90-min peritoneal dialysis dwell was performed. Clearance of tracers to dialysate and permeability-surface area product for glucose were assessed. Transvascular protein transport was higher in Cav-1-KO compared with control mice. Albumin clearance from plasma to peritoneum was 0.088 +/- 0.008 mu l/min in control and 0.179 +/- 0.012 mu l/min in Cav-1-KO (P = 0.001) mice. IgM clearance was 0.049 +/- 0.003 and 0.083 +/- 0.010 mu l/min in control and Cav-1-KO mice, respectively (P = 0.016). Ficoll clearance was increased in Cav-1-KO mice. In conclusion, the lack of caveolae in Cav-1-KO mice resulted in a marked increase in macromolecular transport. A two-pore analysis of the Ficoll clearance data revealed that the higher transport rate in Cav-1-KO mice was not compatible with the appearance of an alternative pathway for macromolecular transport. In contrast, the higher transperitoneal protein and Ficoll clearance is consistent with passive porous transport through an unperturbed two-pore system, presumably at an elevated capillary hydraulic pressure. Alternatively, the data may be explained by reductions in the selectivity of the endothelial glycocalyx, leading to an increased capillary hydraulic conductivity and large solute filtration.
|
|
| 8. |
- Asgeirsson, Daniel, et al.
(författare)
-
Glomerular sieving of three neutral polysaccharides and bikunin in rat. - Effects of molecular size and conformation.
- 2007
-
Ingår i: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 191:3, s. 237-246
-
Tidskriftsartikel (refereegranskat)abstract
- Aim: Polysaccharides and many other non-protein polymers generally have a more open, flexible and asymmetrical structure compared with globular proteins. For a given molecular weight (MW), the Stokes–Einstein radius (ae) of the following polymers increases in the order: Ficoll < dextran ≤ pullulan < polyethylene oxide (PEO). We have tested the hypothesis that such an increase in 'molecular extension' will increase the molecule's glomerular permeability. Thus, we investigated the glomerular sieving coefficients (θ) of the mentioned polymers and of the negatively charged and extended protein bikunin. Methods: In anaesthetized Wistar rats, glomerular sieving curves were generated for each FITC-labelled polymer from their respective concentration in urine and plasma, determined by size exclusion chromatography. The θ for bikunin was measured using a tissue uptake technique. Results: For a molecule of ae = 55 Å (cf. IgG), θ increased in the order: Ficoll (0.00035 ± 0.000013) < dextran (0.022 ± 0.0029) < pullulan (0.033 ± 0.0024) < PEO (0.12 ± 0.0055). For ae = 36 Å (cf. albumin) the order was: Ficoll (0.076 ± 0.0061) < dextran (0.45 ± 0.037) = pullulan (0.45 ± 0.021) < PEO (0.65 ± 0.0076). θ for bikunin (0.089 ± 0.0045) was 150 times higher than that of albumin, having an equivalent ae and net negative charge. Conclusion: From these results it is concluded that for flexible and asymmetric macromolecules, their degree of glomerular hyperpermeability is proportional to their degree of 'molecular extension'. Thus, compared with globular proteins, the polysaccharides investigated, including Ficoll, were found to be hyperpermeable across the glomerular filter in vivo.
|
|
| 9. |
- Asgeirsson, Daniel, et al.
(författare)
-
Increased glomerular permeability to negatively charged Ficoll relative to neutral Ficoll in rats.
- 2006
-
Ingår i: American Journal of Physiology: Renal, Fluid and Electrolyte Physiology. - : American Physiological Society. - 0363-6127. ; 291:5, s. 1083-1089
-
Tidskriftsartikel (refereegranskat)abstract
- It is established that the glomerular filter sieves macromolecules based on their size, shape, and charge. Anionic proteins are thus retarded compared with their neutral or cationic counterparts. However, recent studies have indicated that charge effects are small, or even "anomalous," for polysaccharides. We therefore investigated the impact of charge on the glomerular permeability to polysaccharides by comparing sieving coefficients ({theta}; primary urine-to-plasma concentration ratio) for negatively charged, carboxymethylated (CM) FITC-Ficoll and FITC-dextran with their neutral counterparts. For these probes, {theta} were determined in anesthetized Wistar rats [269 ± 2.7 g (±SE; n = 36)], whose ureters were cannulated for urine sampling. The glomerular filtration rate was assessed using FITC-inulin. Polysaccharides were constantly infused, and after equilibration, urine was collected and a midpoint plasma sample was taken. Size and concentration determinations of the FITC-labeled polysaccharides were achieved by size-exclusion HPLC (HPSEC). For CM-Ficoll, {theta} was significantly increased (32 times at 55 Å) compared with that of uncharged Ficoll. A small increase in {theta} for CM-dextran compared with neutral dextran was also observed (1.8 times at 55 Å). In conclusion, negatively charged Ficoll relative to neutral Ficoll was found to be markedly hyperpermeable across the glomerular filter. Furthermore, negatively charged Ficoll was observed to be larger on HPSEC compared with its neutral counterpart of the same molecular weight. It is proposed that the introduction of negative charges in the "dendrimeric," cross-linked Ficoll molecule may alter its configuration, so as to make it more extended, and conceivably, more flexible, thereby increasing its glomerular permeability. charge barrier; capillary permeability; macromolecules; fractional clearance; reflection coefficients IT IS GENERALLY ACCEPTED THAT the glomerular filter discriminates among macromolecules based on their size, shape, and net charge (6, 8). With respect to charge, the permeability of anionic dextran sulfate was found to be reduced and that of cationic, diethylaminoethyl (DEAE) dextran to be increased compared with that of neutral dextran (6). However, more recent studies have indicated that sulfated dextran may be processed in the kidney (28) and desulfated during its renal passage (10), and furthermore, that it may bind to plasma proteins (17), and to membrane phospholipids (25), causing an artifactual reduction in the sieving coefficients ({theta}; i.e., the primary urine-to-plasma concentration ratios) of dextran sulfate. In addition, isolated glomerular basement membranes (GBM) have generally failed to show charge selectivity when probed with neutral and negatively charged Ficoll (7) or native (anionic) or cationized albumin (4). In line with these findings, Schaeffer et al. (26) were unable to find (in rats in vivo) any difference between glomerular {theta} to carboxymethylated (non-sulfated) dextran or to hydroxymethyl starch (HES), both negatively charged, and their neutral counterparts. Furthermore, the HES molecules showed lower {theta} for any given Stokes-Einstein (SE) radius (cf. Ficoll) than did dextran. It was concluded that the glomerular filtration barrier restricts the transport of polysaccharide macromolecules as a function of size and configuration whereas the presence or absence of negative charge does not play any role. Further supporting these results, Guimarães et al. (18) did not find a decrease in glomerular permeability to negatively charged, carboxymethylated (CM) Ficoll compared with uncharged Ficoll, confirming a previous observation by Greive et al. (16). Instead, they found a markedly increased glomerular permeability to CM-Ficoll. In contrast to the apparent inability of the glomerular filter to discriminate between polysaccharides of different charge, there is ample evidence that, indeed, the glomerular filter selects globular proteins based on their charge. Thus anionic proteins are retarded compared with neutral and cationic proteins, as extensively reviewed by Comper and Glasgow (9) and Venturoli and Rippe (29). The reason the glomerular capillary wall exhibits low discrimination ability with respect to differently charged polysaccharides, while being able to separate proteins of different molecular charge, is obscure. However, one clue to this enigma could be the fact that carbohydrates exhibit an extended molecular configuration, with a larger SE radius, compared with that for globular proteins, for any given molecular mass (19, 29). Such an extended configuration, conceivably, generates a more flexible (compressible) structure and hence increases the molecule's permeability through the glomerular filtration barrier (29). Charge modification of a polysaccharide may lead to a further increase in molecular extension, favoring an increased flexibility and, thereby, an increased solute permeability. Could the process of charge modification of the highly cross linked and "ellipsoid" molecules of Ficoll (19) lead to conformational alterations, with increased molecular extension, increasing their permeability compared with their uncharged counterparts? If so, would the linear, "random coil," structure of dextran make it less affected by conformational changes, and thereby less hyperpermeable, when negatively charged? The present study was performed to test this hypothesis by comparing glomerular sieving coefficients to negatively charged, CM-Ficoll and -dextran vs. their uncharged molecular equivalents.
|
|
| 10. |
- Asgeirsson, Daniel, et al.
(författare)
-
Similitude of permeabilities for Ficoll, pullulan, charge-modified albumin and native albumin across the rat peritoneal membrane.
- 2009
-
Ingår i: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 196:4, s. 427-433
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract Aim: Compared to neutral globular proteins, neutral polysaccharides, such as dextran, pullulan and Ficoll, appear hyperpermeable across the glomerular filtration barrier. This has been attributed to an increased flexibility and/or asymmetry of polysaccharides. The present study investigates whether polysaccharides are hyperpermeable also across the continuous capillaries in the rat peritoneum. Methods: In anesthetized Wistar rats, FITC-Ficoll or FITC-pullulan together with (125)I-human serum albumin (RISA) or neutralized (125)I-bovine serum albumin (nBSA) were given intravenously, after which peritoneal dialysis using conventional peritoneal dialysis fluid (Gambrosol 1.5%) was performed for 120 min. Concentrations of FITC-polysaccharides and radioactive albumin species in plasma and dialysis fluid were analyzed with high performance size exclusion chromatography and a gamma counter, respectively. Transperitoneal clearance values were calculated for polysaccharides in the molecular radius range 36-150 A, and for RISA and nBSA. Results: Ficoll and pullulan showed more or less identical permeabilities, compared to RISA and nBSA, across the peritoneal membrane. Although RISA-clearance, 5.50+/-0.28 (muL/min; +/-SEM), tended to be lower than the clearances of Ficoll(36A) (6.55+/-0.25), pullulan(36A) (6.08+/-0.22) and nBSA (6.56+/-0.23), the difference was not statistically significant. This is in contrast to the hyperpermeability exhibited by polysaccharides across the glomerular filtration barrier and also contrasts with the charge selectivity of the latter. Conclusion: The phenomenon of molecular flexibility is more important for a macromolecule's permeability through the glomerular filter than across the continuous peritoneal capillary endothelium. Furthermore, it seems that charge plays a subordinate role in the steady-state transport across the combined peritoneal capillary-interstitial barrier.
|
|
