The effects of dietary calcium and phosphorus on the retention and excretion of lead in rats

Abstract

1. Rats were given diets containing different amounts of calcium, phosphorus and lead.2. Pb retention was greatly increased when the diets contained less Ca or P than the minimum estimated requirement of the rat.3. The release of Pb already incorporated into the skeleton was inhibited by diets low in Ca but was not affected by diets low in P.4. The retention of Pb given intraperitoneally was not affected by dietary Ca or P.5. It can be concluded that dietary Ca and P influence the absorption of Pb by the gut and dietary Ca influences the metabolism of Pb in the bone.6. There were changes in the distribution of Pb among the tissues due to changes of dietary Ca.7. At low body concentrations, Pb probably affected skeletal growth.

Lead toxicity and nutritional deficiencies.

“…Rather, calcium-deprived rats had decreased excretion and thus increased body retention of lead. This observation agrees with the work of Quarterman and Morrison (29), who noted that the release of lead already incorporated into the skeleton as a result of previous lead dosing was inhibited by the subsequent feeding of diets low in calcium. The physiological mechanism whereby low calcium diets increase lead retention is not known, but Goyer speculated that the site of action may be the kidney (25).…”

“…Barltrop and Khoo showed that halving the recommended level of phosphate increased lead uptake by rats in shortterm experiments but to a slightly lesser degree than halving the calcium (27). On the other hand, Quarterman and Morrison found that feeding 33 and 70% of the recommended levels of calcium and phosphate, respectively, caused similar increases in lead retention in long-term studies (29). Both groups agreed that feeding diets low in both calcium and phosphate resulted in roughly additive effects on lead uptake or retention.…”

Lattice parameters and cation distribution of solid solutions of calcium and lead hydroxyapatite

“…[20], phosphorus [8,15], and sulfur [21,22]. The disappearance curves for lead excretion in blood, plasma, hematic cells, and some other soft tissues can be expressed as sums of exponential functions.…”

“…Infants have a relatively high retention as compared to adults [7]. Indications have been found that lead interferes with the metabolism of calcium [8][9][10][11][12][13][14][15][16], magnesium [17], strontium [9], copper [1,18], iron [18,19]…”

Indices of potential lead hazard.

“…An alteration in bone or teeth of binding, more permanent deposition and the redistribution of lead would be expected in association with a variety of normal and clinical conditions, for example: (a) during early development, (b) continued growth at the epiphyses until maturity, (c) conditions that involve bone remodeling or resorption and (d) during pregnancy (69,(91)(92)(93). At these times, the lead may be more mobile than in quiescent periods.…”