Application of ion-selective microelectrodes to the detection of calcium release during bone resorption

In this work we apply calcium ion-selective liquid membrane microelectrodes to the investigation of the release of ionised calcium in real-time from b ovine cortical bone slices in the presence of osteoclasts. The osteoclast i s the cell responsible for the resorption (dissolution) of bone and excess bone resorption is implicated in diseases such as osteoporosis. Pretreatmen t of the bone slice with dilute solutions of ammonium fluoride was found to result in greater resistance to osteoclastic resorption. However, a detect able calcium Bur was still observed indicating that the cells were able to attach to the fluoride treated bone and carry out resorption. These data we re confirmed by scanning electron microscopy which indicated that the numbe r of bone resorption pits was not affected by the fluoride treatment, altho ugh the excavated area was markedly decreased in the presence of fluoride. The results of these studies indicate that the use of calcium-selective mic roelectrodes provide a feasible alternative assay of osteoclast activity to the conventional electron microscopic assay. The microelectrode technique enables real-time data to be obtained, whereas the conventional method requ ires a long (ca. 16-20 h) incubation of the cells on the bone slice. (C) 19 99 Elsevier Science Ltd. All rights reserved.