AJP - Renal Physiology, Vol 264, Issue 4 752-F759, Copyright © 1993 by American Physiological Society
Effect of phosphorus restriction on renal response to oral and intravenous protein loads in rats
E. S. Kraus, L. Cheng, I. Sikorski and D. A. Spector
Division of Renal Medicine, Francis Scott Key Medical Center, Johns Hopkins School of Medicine, Baltimore, Maryland.
Dietary phosphorus restriction ameliorates renal injury in rats. This may
be due to changes in renal hemodynamics, including those factors associated
with protein-induced hyperfiltration. To test this, we measured inulin
clearance (CIn), p-aminohippuric acid clearance (CPAH), mean arterial blood
pressure, and renal vascular resistance (RVR) 1 h before and 100 min after
either oral gavage of 2 g bovine serum albumin or intravenous infusion of
5% glycine in female Sprague-Dawley rats previously fed for 3-8 wk a 0.5%
or a 0.1% phosphorus diet. Baseline CIn, CPAH, blood pressure, and RVR were
similar. After albumin gavage, CIn rose 20% (P < 0.01) for the 0.5%
phosphorus group but did not change for rats fed the 0.1% phosphorus diet.
Other measured parameters, including plasma glucagon and renin activity,
were not influenced by dietary phosphorus content. In contrast, during
intravenous infusion of glycine, hyperfiltration was induced in
phosphorus-restricted rats. Thus dietary phosphorus restriction ablates
oral protein but not intravenous amino acid-induced hyperfiltration,
suggesting a gut-mediated mechanism for the former. These data highlight
the potential importance of dietary phosphorus as a mediator of renal
hemodynamics.
