Bone mineral and aluminum concentrations in patients undergoing CAPD.

CAPD results in continuous peritoneal transfer of hormones and minerals involved in the pathogenesis of renal osteodystrophy (RO). Moreover, although CAPD patients seem to have better control of serum phosphate concentration than hemodialysis patients, the need for aluminum-containing phosphate binders (ACPB) may still be present. In a prospective study meant to investigate the evolution of RO, we obtained 79 bone biopsies in 29 uremic patients (20 male, 9 female; age 25-59, mean 46). Of these, 22 were obtained at the beginning of treatment, 24 after 24 months, 23 after 36 months and 10 after 60 months. All patients were treated with CAPD (Viaflex, Baxter 2-2.5 L x 4-5 bags/day; Ca(++) + 3.5, Mg(++) 1.5 mEq/L) as the first modality of therapy and received oral calcitriol, aluminum hydroxyde and/or calcium carbonate and magnesium hydroxyde in order to maintain serum calcium (Ca) and phosphorus within the normal range. Qualitative bone histology, bone Ca and magnesium (Mg) (Flame atomic absorption spectroscopy) and aluminum (Al) concentration (Graphite furnace atomic absorption spectrometry) were determined. CAPD achieves a good control of RO as indicated by the tendency toward a decreased incidence of mixed osteodystrophy and predominant hyperparathyroid bone disease and improvement of osteoid lesions. A defective Ca content of bone is persistent in the observed period and positively correlated to bone Mg concentration. An increased level of Al was shown in the serum and bone. The highest bone Al content was found among patients with predominant osteoid bone disease. Also in CAPD, patients consuming ACPB are at risk of bone Al accumulation despite the low Al levels in the dialysate.

Aluminum removal after chronic intoxication in rats.

Aluminum concentrations were measured in serum and in the bone, liver, spleen, kidney and brain of male Wistar rats treated with aluminum lactate. The administration was performed intraperitoneally over a period of 109 days, giving a total elemental aluminum dose of 128 mg per rat. After loading, a group of animals was killed together with blanks to verify the level of aluminum accumulation. Two groups of remaining rats were administered with deferoxamine over a period of six and fifteen weeks, respectively, receiving total doses of 270 and 675 mg of DFO. The concentrations of aluminum in serum and in tissues were compared with those found in other groups of animals undergoing aluminum suspension. The determination of iron in liver was also performed. Results indicate that in this experimental model the action of deferoxamine was preferential toward tone while it seemed lacking in the other examined tissues.

Predictive value of serum aluminium levels for bone accumulation in haemodialyzed patients.

Uremic patients undergoing long-term dialysis risk accumulating tissue aluminium burdens and developing aluminium-related syndromes, such as dialysis encephalopathy and osteomalacia. A statistical retrospective study on 253 uremic subjects was carried out to verify the predictive value of serum aluminium levels on bone aluminium accumulation. Serum and bone samples collected at the same time were analyzed for aluminium content. Analyses were performed by graphite furnace atomic absorption technique. The results verified bone aluminium concentrations of less than or equal to 60 mg/kg d.w. (dry weight) in 144 patients and greater concentrations in 109 patients. The statistical discriminant analysis showed that serum levels can be predictive in aluminium bone accumulation (lower or greater than 60 mg/kg) with about a 7% margin of error. This value may be further reduced to about 2% if two threshold limits are used (53-81 micrograms/l). The specificity and sensitivity of the test were 89.6% and 83.5%, respectively.