| Abstrakt: |
The present study was undertaken to test the in vitro action of aluminum on bone phosphatase activities and the possible interaction of this metal with parathyroid hormone (bPTH) or vitamin D dihydroxymetabolites [1,25- and 24,25(OH)D). Three-day-old rat calvaria were incubated for 24 h with one of the following: bPTH at 5×10M, 1,25-or 24,25(OH)D at 2.5×10M, Al at concentrations ranging from 3×10M to 6×10M, or their corresponding solvents. Al effects were also investigated when the medium phosphate or calcium concentrations were modified. In some experiments, Al was added simultaneously with bPTH or one of the vitamin D metabolites at the beginning of the 24 h incubation. At the end of all incubations, acid and alkaline phosphatase activities were measured in bone cytoplasmic extract. The results show that: (a) When compared to the value found in half calvaria incubated in a control medium, the bone acid and alkaline phosphatase content is significantly higher in paired halves incubated with Al (3×10M to 1.5×10M) as well as with bPTH, 1,25-, or 24,25(OH)D and sharply decreased with higher Al concentrations (6×10M). (b) The Al effect on phosphatase activities is modified in a free phosphate or a free calcium medium. (c) The presence of Al at 1.5×10M or 6×10M significantly decreases the bPTH or 1,25(OH)D-induced stimulation of bone phosphatase activities. (d) A similar interaction could not be found between Al and 24,25-(OH)D. [ABSTRACT FROM AUTHOR] |
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