Effect of Dietary Phosphorus Deprivation on Renal Handling of Calcium and Phosphorus

Author(s):  
Nama Beck
1974 ◽  
Vol 25 (1) ◽  
pp. 147 ◽  
Author(s):  
J Leibholz

The flow of calcium and phosphorus to the proximal duodenum was measured over 22 24-hr periods in sheep fitted with re-entrant duodenal cannulae. The sheep were offered one of six diets in a ground and pelleted form supplying 1.4–30 g of nitrogen per day from three different protein sources. The estimated metabolizable energy content of the diets was 1.9 or 1.3 Mcal/kg. The diets supplied 2.0–5.8 g of calcium per day and 2.2–3.3 g of phosphorus per day. Between 49.9% and 61.2% of the dietary calcium intake appeared at the duodenum in the sheep given all diets except the one supplying 1.4 g of nitrogen per day, where the value was 98.5%. There were highly significant correlations between the daily calcium intake and the flow of calcium to the duodenum, the excretion of calcium in the faeces, the retention of calcium and the calcium content of the rumen. Between 85.0 and 119.1% of the daily phosphorus intake appeared at the duodenum in the sheep given all six diets. The flow of phosphorus was correlated with the dietary phosphorus intake. There were significant correlations between the flow of calcium and phosphorus to the duodenum and, also, their retention.


1964 ◽  
Vol 82 (1) ◽  
pp. 111-114 ◽  
Author(s):  
E. R. Miller ◽  
D. E. Ullrey ◽  
C. L. Zutaut ◽  
J. A. Hoefer ◽  
R. W. Luecke

1966 ◽  
Vol 20 (3) ◽  
pp. 561-569 ◽  
Author(s):  
G. E. Harrison ◽  
G. R. Howells ◽  
Jill Pollard ◽  
Krista Kostial ◽  
R. Manitaševi´c

1. After feeding radioactive markers 85Sr and 45Ca for 10 days to weanling and adult rats receiving basal diets all of which contained adequate calcium and phosphorus to support normal growth, the skeletal retention of the markers was compared with that in litter-mates receiving seven different P compounds as dietary supplements so that the P intake was increased 2 to 3½ times. 2. In weanling rats a dietary supplement of KH2PO4 decreased the skeletal retention of 85Sr by some 30% without affecting the retention of 46Ca. In adults on this supplement, the skeletal retention of 85Sr was reduced by over 40% compared with controls on the same basal diet. 3. When the supplement contained Ca as well as P the reduction in skeletal retention of 85Sr in young and adult rats was greater than when no Ca was present in the supplement. 4. It is concluded that there was no experimental evidence to show that supplements of P which also contained Ca induced any Ca deficiency in the rats. 5. In rats receiving P supplements which also contained Ca, the ratio of the skeletal retention of 85Sr, experimental to controls, was 0.45 for weanling rats and 0.52 in adults, 34 weeks old. These ratios were not significantly different for any of the seven supplements used. 6. From comparisons with previous experiments, it is concluded that supplementation with Ca plus P is more promising as a remedial measure for decreasing the uptake of radioactive Sr from the diet than supplementation with Ca alone.


1992 ◽  
Vol 17 ◽  
pp. 215
Author(s):  
R. Villar ◽  
C. Caballero ◽  
M. Abasta ◽  
A. Mondragón ◽  
A. Armenta ◽  
...  

2009 ◽  
Vol 296 (6) ◽  
pp. F1376-F1385 ◽  
Author(s):  
Ignacio Lopez ◽  
Francisco J. Mendoza ◽  
Fatima Guerrero ◽  
Yolanda Almaden ◽  
Charles Henley ◽  
...  

The purpose of the present study was to test the hypothesis that extraskeletal calcification regresses in uremic rats after reduction in phosphorus intake and treatment with calcimimetics. Extraosseous calcification was induced in five to six nephrectomized rats fed a high-phosphorus (1.2%) diet who received calcitriol (80 ng/kg ip) every other day for a period of 14 days. Next, dietary phosphorus was reduced to 0.6%, and rats were treated with vehicle ( n = 20), calcitriol [80 ng/kg ip/48 h ( n = 20)], or the calcimimetic AMG 641 [1.5 mg/kg sc/48 h ( n = 20)]. Aortic and soft-tissue calcium and phosphorus content was evaluated after 14 and 28 days. At 28 days, reduction of phosphorus intake resulted in a significant decrease in tissue mineral content in vehicle- and AMG 641-treated rats but not in rats receiving calcitriol. Aortic calcium and phosphorus was lower in rats treated with AMG 641 (96.7 ± 26.4 mg/g) than in rats receiving vehicle (178.3 ± 38.6 mg/g). An infiltrate of phagocytic cells expressing the calcium-sensing receptor was identified in areas surrounding foci of calcification. Additional studies in parathyroidectomized rats demonstrated that AMG 641 increased the urinary excretion of calcium (6.2 ± 0.6 vs. 3.1 ± 0.5 mg/day, vehicle) ( P < 0.001). In conclusion, experimentally induced extraosseous calcification in uremic rats can be partially resolved by reducing phosphorus intake; the addition of calcimimetics may accelerate the regression process through mechanisms potentially involving a direct stimulatory effect on mineral phagocytic cells plus an increase in urinary calcium excretion.


2013 ◽  
Vol 304 (3) ◽  
pp. E310-E320 ◽  
Author(s):  
Stephen J. Quinn ◽  
Alex R. B. Thomsen ◽  
Jian L. Pang ◽  
Lakshmi Kantham ◽  
Hans Bräuner-Osborne ◽  
...  

Calcium and phosphorus homeostasis are highly interrelated and share common regulatory hormones, including FGF23. However, little is known about calcium's role in the regulation of FGF23. We sought to investigate the regulatory roles of calcium and phosphorus in FGF23 production using genetic mouse models with targeted inactivation of PTH (PTH KO) or both PTH and the calcium-sensing receptor (CaSR; PTH-CaSR DKO). In wild-type, PTH KO, and PTH-CaSR DKO mice, elevation of either serum calcium or phosphorus by intraperitoneal injection increased serum FGF23 levels. In PTH KO and PTH-CaSR DKO mice, however, increases in serum phosphorus by dietary manipulation were accompanied by severe hypocalcemia, which appeared to blunt stimulation of FGF23 release. Increases in dietary phosphorus in PTH-CaSR DKO mice markedly decreased serum 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] despite no change in FGF23, suggesting direct regulation of 1,25(OH)2D3 synthesis by serum phosphorus. Calcium-mediated increases in serum FGF23 required a threshold level of serum phosphorus of about 5 mg/dl. Analogously, phosphorus-elicited increases in FGF23 were markedly blunted if serum calcium was less than 8 mg/dl. The best correlation between calcium and phosphorus and serum FGF23 was found between FGF23 and the calcium × phosphorus product. Since calcium stimulated FGF23 production in the PTH-CaSR DKO mice, this effect cannot be mediated by the full-length CaSR. Thus the regulation of FGF23 by both calcium and phosphorus appears to be fundamentally important in coordinating the serum levels of both mineral ions and ensuring that the calcium × phosphorus product remains within a physiological range.


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