AJP - Renal Physiology, Vol 248, Issue 1 64-F69, Copyright © 1985 by American Physiological Society
Effect of aluminum on the renal handling of phosphate in the rat
M. Burnatowska-Hledin, A. M. Klein and G. H. Mayor
The effects of aluminum (Al) on the renal handling of phosphate (Pi) were
studied by clearance techniques in the presence and absence of endogenous
parathyroid hormone (PTH) and after Pi infusion. In all groups, a 1-h
control period was followed by three 1-h experimental periods in which
controls continued to receive saline and experimental animals received Al.
Glomerular filtration rate, urine flow rate, and plasma sodium (Na) were
not significantly changed between periods in any group. In the presence of
endogenous PTH, the fractional excretion of phosphate (FEPi) increased
significantly after 3 h of Al infusion (6.1 +/- 0.9 to 15.0 +/- 1.8%, P
less than 0.05, n = 8), but not in controls (n = 7), while plasma calcium
and Pi decreased, suggesting a PTH effect. However, in acutely
thyroparathyroidectomized (TPTX) rats the FEPi also increased significantly
after 3 h of Al infusion (4.3 +/- 3.0 to 10.6 +/- 4.2%, P less than 0.05, n
= 7), but not in controls (n = 6). In TPTX rats infused with Pi where
plasma Pi was increased to 10 mg/dl, FEPi increased significantly after 2
and 3 h of Al (7.0 +/- 1.4 to 15.5 +/- 2.1 to 16.9 +/- 2.2%, P less than
0.01, n = 15), but not in controls (n = 8). In this group, changes in FEPi
were accompanied by a small but significant increase in FENa but not
urinary cAMP. Blood pH was not significantly different between saline and
Al-infused rats. These studies indicate that Al infusion inhibits renal Pi
reabsorption by a mechanism independent of PTH, blood pH, or cAMP.
