Epiphyseal cartilage cAMP changes produced by electrical and mechanical perturbations

Epiphyseal cartilage from chick embryo was subjected in vitro for one to 15 minutes to static compressive forces or oscillating electric fields. The same stimuli were applied to suspensions of cells isolated from the epiphyses. At the end of the perturbation cAMP was measured in the tissue or cell extracts by radioimmunoassay. It was found that a physiological (60 g/cm2) static pressure reduced the cAMP content in the tissue and the separated cells. An oscillating electric field above 900 V/1.5 cm, 5Hz, enhanced the cAMP accumulation in the intact tissue. This effect was produced only when the long axis of the bones was oriented parallel to the electric field. In isolated cells an electric field above 750 V/1.5 cm, 5Hz, caused a decrease in cAMP content. Charged matrix macromolecules and orientation of the cells within the cell matrix may have a modulating effect on the initiation of this response. It is postulated that the change in cAMP is the early cellular signal in the response to an electrical or mechanical perturbation which leads to bone remodeling.