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The rat glomerular filtration barrier does not show negative charge selectivity.
Richard C Schaeffer1, Max L Gratrix, David R Mucha
1Department of Physiology, The University of Arizona, Tucson, AZ, USA. rcschaeffer@earthlink.com
Microcirculation (New York, N.Y. : 1994)
|October 11, 2002
Summary
The glomerular filtration barrier restricts macromolecule transport based on size and shape, not negative charge. This study used fluorescent tracers to analyze how size and charge affect macromolecule movement across the kidney
Area of Science:
- Nephrology
- Renal Physiology
- Biophysics
Background:
- The glomerular filtration barrier's selectivity is crucial for kidney function.
- Understanding macromolecule transport informs diagnosis and treatment of kidney diseases.
Purpose of the Study:
- To investigate the influence of size, shape, and negative charge on macromolecule transport across the glomerular capillary wall.
- To establish sieving curves for various polysaccharide tracers.
Main Methods:
- Measured glomerular fractional clearances (FC) of neutral and negatively charged dextrans (DEX), hydroxyethyl starch (HES), and bovine serum albumin (BSA) in rats.
- Utilized fluorescent tracers and inulin clearance to determine glomerular filtration rate.
- Assessed in vitro uptake of probes by endothelial and renal proximal tubule cells.
Main Results:
- Sieving curves for neutral and negatively charged DEX were identical, indicating charge independence.
- FC values for DEX were significantly higher than for HES and BSA.
- BSA showed substantially greater uptake by renal tubule cells compared to other probes.
Conclusions:
- The rat glomerular filtration barrier's restriction of polysaccharide macromolecule transport is primarily dependent on size and configuration, not negative charge.
- These findings clarify the mechanisms of glomerular filtration and macromolecule handling by the kidney.