Biochemical pathways involved in the translation of physical stimulus into biological message.

Studies from our laboratory revealed that direct application of physical strain (PS) to cultured bone cells stimulated synthesis of prostaglandin E2 (PGE2) in a specific population of cells. We found that PGE2 induced the cellular production of cAMP in several bone cell types, whereas the induction of DNA synthesis was limited to osteoblastlike cells. Indirect evidence indicated that PS induced the osteoblastlike cells to synthesize PGE2. Other cell types, for example, chondrocytes, when activated by PS, can be induced to produce cAMP and induce DNA synthesis not mediated by PGE2. We have also found that electric stimulation of different populations of bone cells is specifically induced by a certain intensity of the electric field. It seems that electric stimulus circumvents the PGE2 effect and triggers the adenyl cyclase system in the cell directly. The electric field also induces DNA synthesis not via PGE2 production.