Direct functional assessment of human osteoblasts by radioautography: methodology and application in end stage renal disease.

Fragments approximately 1 mm3 of freshly obtained iliac crest cancellous bone were incubated for 30 minutes at 37 degrees C in Krebs buffer containing 3H-leucine or 3H-proline followed by radioautography. Grains per osteoblast, reflective of protein synthetic activity, were counted in normal controls and patients with end stage renal disease with or without significant aluminum storage in their bones. Compared with control the end stage renal disease patients without significant aluminum storage had more large osteoblasts with increased grain counts which were ascribed to secondary hyperparathyroidism. Cells from patients with greater than 30% surface aluminum had more small osteoblasts with grain counts intermediate between control and less than 2% aluminum, ascribed to an inhibitory effect of aluminum on the secondary hyperparathyroidism. Cell activity did not depend on location next to a tetracycline label or osteoid and it was suggested that all bone lining cells could be considered as osteoblasts. Aluminum storage was associated with impaired mineralisation in the presence of normal or increased osteoblastic protein synthetic activity suggesting that in these patients the mineralisation defect was not primarily due to an abnormality in osteoblast function.