OSTEOBLAST ADHERENCE AND RESORPTION ACTIVITY OF ISOLATED OSTEOCLASTS ON CALCIUM-SULFATE HEMIHYDRATE

The adherence of osteoblast-like cells and the resorption activity of isolated osteoclasts on calcium sulphate hemihydrate (CSH) was investi gated. After a 24 h incubation period, alkaline phosphatase staining s howed that rat osteoblast-like cells ROS 17/2.8 attached on CSH. Neutr al red (NR) and tartrate-resistant acid phosphatase (TRAP) staining re vealed that osteoclasts attached on CSH. Furthermore, osteoclasts form ed lacunae as revealed by scanning electron microscopy. Although the l acunae formed by osteoclasts on CSH were diverse in shape and form, th e most common type had approximately a circular outline, with a well-d efined margin similar to those formed on dentine. Less commonly, excav ations appeared as a discontinuous area of resorbed CSH with the prese nce of a circular zone around the non-resorbed area. Finally, by using 10(-9) M calcitonin, evidence was obtained that NR-positive cells wer e osteoclasts (58.3% and 57.66% decrease of NR-positive mouse and rat cells detected on CSH after 24 h incubation). However, no inhibition w as obtained with 10(-11) M calcitonin. The overall number of NR-positi ve osteoclasts adherent on 256 mm(2) CSH was 43 +/- 14 and 42 +/- 3 fo r mice and rat, respectively. The overall number of TRAP-positive mous e osteoclasts was 67 +/- 12. Acetazolamide (10(-5) M), a carbonic anhy drase inhibitor, inhibited the number of adherent NR osteoclasts on CS H by 50.42% and 41.6% for mouse and rat, respectively. These results i ndicate that osteoblasts attach on CSH and osteoclasts resorb CSH in v itro.