Dynamic, size-selective effects of protamine sulfate and hyaluronidase on the rat glomerular filtration barrier in vivo

Abstract

The proteinuric actions of protamine sulfate (PS) have classically been, at least partly, attributed to alterations of the negatively charged glomerular endothelial glycocalyx. 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 with 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 glycocalyx, 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 to assess glomerular sieving coefficients (θ) for Ficoll (radius 10-80 Å). The GFB showed a significant glomerular charge selectivity for Ficoll molecules of radius 20-35 Å. PS and hyase infusions reversibly increased θ for large Ficoll molecules (Ficoll molecules of radius 50-80 Å). Thus, for PS, θ for a-Ficoll molecules of radius 70 Å increased from 2.47 × 10(-5) ± 1.1(-5) to 7.25 × 10(-5) ± 1.1(-5) (P < 0.05) at 15 min. For hyase, changes in a-Ficoll molecules of radius 50-80 Å were, however, not statistically significant. Neither PS nor hyase had any effect on θ for n-Ficoll molecules of radius 20-45 Å or a-Ficoll molecules of radius 20-45 Å. 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.

Essential role and therapeutic targeting of the glomerular endothelial glycocalyx in lupus nephritis

“…H degrades HA glycosaminoglycans from the glycocalyx (50). Also, it has been established that H injection does not affect glomerular charge selectivity and does not cause significant increases in the glomerular permeability of macromolecules (51). We show here by the reduced FITC-WGA lectin fluorescence intensity that H significantly diminished the accumulated glomerular endothelial glycocalyx in LN and efficiently reduced its HA content as demonstrated by reduced HABP labeling ( Figure 5 and Figure 6).…”

Continuum of historical controversies regarding the structural-functional relationship of the glomerular ultrafiltration unit

“…Certainly, their studies supported previous observations that the GUU is a chargeselective barrier since inert dextran or Ficoll with similar hydrodynamic radii comparable with that of anionic albumin (pI Ϸ 4.9, Ϸ36 Å) has an Ϸ100-fold higher value (0.02-0.1 vs. 0.0006) (11). The results of studies by Sverrisson et al (28) were more or less similar to seminal observations made by Brenner et al (2), and it seems that charge selectivity prevails over a relatively wide range of hydrodynamic radii, i.e., 20 -35 vs. 18 -44 Å. In this regard, results from a study (20) on the quantification of electrostatic properties suggested that although electrical charge makes a moderate contribution, it is capable of almost totally excluding albumin permeating via high-selectivity pathways in a charged-fiber matrix of the glomerular filtration barrier.…”

“…Another major point the authors have made in this article is that the functionalities of the GUU mainly reside at the level of glomerular endothelial cell surfaces coated by a glycocalyx enriched with hyaluronic acid since treatment with PS and hyaluronidase affected size-selective permeability characteristics of the GUU (28). Besides hyaluronic acid, the glycocalyx has also been described to be enriched with sialoglycoproteins and sulfated proteoglycans, which can conceivably also contribute both charge and size selectivity to the GUU since a reduced volume of glycocalyx and increased expression heparanase is seen in proteinuric states and both neuraminidase or heparanase treatment leads to a similar reduction in the density/ volume of glycocalyx (10, 15, 16).…”

“…In an article by Sverrisson et al (28) in a recent issue of the American Journal of Physiology-Renal Physiology, the authors described that the GUU maintains charge selectivity mainly toward "small molecules" like Ficoll with hydrodynamic radii of 20 -35 Å, whereas PS and hyaluronidase infusions predominantly affect the glomerular sieving coefficient () of large anionic Ficoll with hydrodynamic radii of 50 -80 Å. They concluded that these properties of the GUU and changes in its are attributable to biochemical characteristics of the endothelial glycocalyx, enriched with hyaluronic acid, a nonsulfated proteoglycan.…”

Repeated Low Intensity Blast Exposure Is Associated with Damaged Endothelial Glycocalyx and Downstream Behavioral Deficits

“…To our knowledge, using hyaluronidase to modify brain endothelial glycocalyx has not been previously studied. The dose of hyaluronidase chosen was based on previous studies of enzymatic modification of the glycocalyx in muscle (500 IU) and kidney (1105 IU) in rats (Eskens et al, 2013; Sverrisson et al, 2014). The 2000 IU/kg dose results in a total dose (500–700 IU) which is within the range of doses shown to have effects in different tissue beds and was adjusted for the weight of the animal.…”