Immuno‐histochemical localization of cyclic nucleotides in mineralized tissues: Mechanically‐stressed osteoblasts in vivo

Previous experiments indicate that bone cells respond to external stimuli with fluctuations of cyclic nucleotide levels. The objective of this experiment was to study the response of alveolar bone to the application of tensile forces through an examination of the osteoblastic staining pattern for cAMP and cGMP. Cat canines were tipped by 80-g force for 0 to 48 hours. Fresh frozen, unfixed, undecalcified jaws were sectioned sagittally and stained immuno-histochemically for cAMP and cGMP. In tension sites, osteoblastic staining intensity for cAMP decreased gradually from one to three hours, and then increased by 24 hours. Intense staining for cGMP, visible in osteoblasts of all treated cats, peaked after three hours of treatment and then again at 24 hours. Generally, groups of cGMP-stained osteoblasts were found adjacent to unstained osteoblasts. The observed fluctuations in the osteoblasts staining pattern for cAMP and cGMP indicates involvement of these substances in the early response of osteoblasts to mechanical stimuli in vivo.