Inhibitory Actions of Calcitonin on Resorbing Bone Explants in Culture and on Their Release of Lysosomal Hydrolases

¹ Laboratory of Physiological Chemistry, University of Louvain, Dekenstraat 6, B3000-Louvain, Belgium

Bone resorption that occurs either spontaneously or under the action of parathyroid extract (PTE), was studied in tissue culture of fetal mouse calvaria, and a system was developed in which calcitonin (CT) inhibited resorption almost completely on the first day of the culture, but only partially on the second day. The excretion of two lysosomal marker enzymes, -glucuronidase and N-acetyl--glucosaminidase, during the resorption processes was suppressed or inhibited by CT; this correlated well with the degree of resorption achieved, as judged by mineral loss and by the appearance of lacunae in the explants. On the first day of culture, CT also prevented the enhancement by PTE of the release of lactate by the explants. These data are compatible with a possible role of the lysosomal enzymes and of the glycolytic production of acid in the resorption processes.