Background: The loss of renal function in chronic kidney disease (CKD) patients leads to a variety of metabolic disturbances that promote the development of secondary hyperparathyroidism (SH) and bone disease. One of these alterations, hyperphosphatemia, is a persistent problem in patients with CKD and is an important factor in the development and severity of SH as well as coronary artery and cardiac valve calcification. To help control serum phosphorus (P), phosphate binders are used to minimize intestinal absorption of P in these patients. Since the use of aluminum- and calcium-based phosphate binders can result in severe side effects, other phosphate binders have been proposed. One of these is lanthanum (La) carbonate.
Methods: Since there is some controversy as to the degree La is absorbed by the intestine, whether it is deposited in tissues, and what effect its prolonged use would have in patients with chronic renal failure, we studied normal and uremic rats fed a control diet or a diet with La carbonate (1.5% elemental La) for 45, 90, or 110 days.
Results: As expected, plasma creatinine increased after the induction of uremia and continued to increase with time. At 45 and 90 days, dietary La produced a reduction in plasma P in normal rats (N + La) [45 days: 3.15 +/- 0.35 vs. normal control (NC) 4.41 +/- 0.15 mg/dL, P < 0.01; 90 days: 3.20 +/- 0.30 vs. 4.09 +/- 0.15 mg/dL, P < 0.05], but not at 110 days. Plasma P was initially lower (45 days) in both groups of La-treated rats (U + La: 3.47 +/- 0.28 vs. UC: 4.91 +/- 0.27 mg/dL, P < 0.01), but was not at 90 and 110 days. Whole blood La content was not increased in rats fed the La diet and is, therefore, not a good indicator of the La content of tissue. La was increased in kidney, femur, and especially liver in normal and uremic rats fed the La diet. Uremia markedly enhanced tissue accumulation of La (liver, 110 days: N + La: 849 +/- 152 vs. U + La: 2676 +/- 479 ng/g wet wt, P < 0.01), which increased in a time-dependent manner. The increase in La in the liver of normal rats was 44-fold compared to control and 98-fold in the liver of uremic rats compared to uremic control.
Conclusion: La accumulates in tissues, most strikingly in the liver, and renal failure accelerates the accumulation. While this was a relatively short-term study, La accumulation increased in a time-dependent manner. The effect of long-term La treatment on patients with chronic renal insufficiency needs to be evaluated.