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Osteoblast-like cells possess Na-dependent transporters which accumulate orthophosphate (Pi) from the extracellular medium. This may be important in bone formation. Here we describe parallel measurements of Pi uptake and cellular [Pi] in such cells from the rat (UMR 106-01 and UMR 106-06) and human (OB), and in non-osteoblastic human fibroblasts (Detroit 532 (DET)). In UMR 106-01, cellular [Pi] was weakly dependent on extracellular [Pi] and higher than expected from passive transport alone. [32Pi]-uptake was inhibited by Na deprivation, but paradoxically increased on K deprivation. With Na, 87 per cent of cellular 32P was found in organic phosphorus pools after only 5 min. Na deprivation also decreased cellular [Pi], in both UMR 106-01 and DET, but the decrease was smaller than that in [32Pi]-uptake. Ouabain decreased [32Pi]-uptake and cellular [Pi] in DET, but not in UMR 106-01. Regulation of cellular [Pi] is therefore at least partly dependent on Na/Pi co-transport, but this does not seem to be an exclusive property of osteoblasts.

Original publication




Journal article


Cell biochem funct

Publication Date





13 - 23


Animals, Biological Transport, Fibroblasts, Humans, Osteoblasts, Ouabain, Phosphates, Potassium, Rats, Sodium, Sodium-Potassium-Exchanging ATPase, Tumor Cells, Cultured