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± 1.1−5to 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.