Successful high-dose calcium treatment of aluminum-induced metabolic bone disease in long-term home parenteral nutrition.

A patient who developed severe metabolic bone disease is presented. He had received long-term home parenteral nutrition (HPN) following extensive small bowel resection after mesenteric vein thrombosis. Bone disease caused by aluminum intoxication had components of osteomalacia and low-turnover osteoporosis. Aluminum was detected at the surface of mineralized bone and was elevated in the serum, resulting in a positive deferoxamine infusion test. One year of treatment with high doses of calcium (up to 24 mEq per day) significantly diminished the patient's bone pain, increased the serum levels of calcium, abolished aluminum deposits in the mineralized trabecula, improved bone formation, and increased trabecular bone volume as assessed by repeated histomorphometric analysis.

Proteoglycan synthesis in vitamin D-deficient cartilage: recovery from vitamin D deficiency.

Vitamin D appears to be required for mineralization of skeletal elements. There is also evidence that cartilage proteoglycans may be involved in the regulation of mineralization. Previous studies have shown an alteration in the structure of the proteoglycans of the epiphyseal growth cartilage as a result of the decrease in serum calcium related to deficiency of dietary vitamin D. Vitamin D deficiency also induces a thickening of the epiphyseal growth plate presumably because of the inhibition of maturation of the growth plate chondrocytes. In order to compare the effect on proteoglycan structure with that on growth plate morphology, the proteoglycans of healing epiphyseal cartilage were characterized. The results indicate that, consistent with previous data, in vitamin D-deficient hatching chicks, the proteoglycans of the growth cartilage, but not of the articular cartilage, are smaller in monomer size with slightly smaller chondroitin sulfate chains whose sulfation pattern is unaltered. Sternal cartilage proteoglycans are unaffected. During recovery from vitamin D deficiency, the proteoglycans isolated from the growth cartilage are still not completely normal one day after supplementation with vitamin D, but are indistinguishable from normal by four days. In addition, the results conflict with those of a previous study in which only growth cartilage of hatchling chicks, not sternal or articular cartilage, was reported to synthesize large proteoglycans. Instead, all of these cartilages in the normal chicken have been found in this study to produce large proteoglycans of a size typical for mammalian cartilage and embryonic chick cartilage.

The metabolism of vitamin D3 during fracture healing in chicks.

The metabolism of vitamin D3 was studied in chicks after experimental fractures were performed on their tibiae. The chicks were fed for 3 weeks a vitamin D-deficient diet but were supplemented with radioactive labeled vitamin D3. The chicks were then divided into two groups. In the first group the right tibia was fractured, whereas the second group served as nonfractured control group. During the following days of fracture healing, the metabolites of [3H]vitamin D3 were measured in callus, epiphysis, diaphysis, plasma, duodenum, and kidney. Histological examination of calluses and bones, measurements of intestinal absorption of calcium, and renal production of dihydroxylated metabolites of vitamin D3 were performed as well. The levels of the dihydroxylated metabolites were increased in the calluses and the levels of [3H]24,25-dihydroxyvitamin D3 were found to coincide with the formation of cartilaginous tissue and with the renal production of this steroid. In the duodenum of the fractured chicks, the levels of [3H]1,25-dihydroxyvitamin D3 dropped significantly during the first week after fracture, coinciding with reduction in the intestinal absorption of calcium. In the plasma during those 3 weeks of healing process the levels of [3H]1,25-dihydroxyvitamin D3 were far below normal. These findings indicate that during the process of fracture repair, changes in the metabolism and expression of vitamin D are taking place in order to meet the new requirements of the body under stress condition of skeletal fracture.