Abstract
Osteocytes, dendritic resident cells in bone, transduce signals of mechanical loading that results in anabolic responses of bone. In our previous report with primary osteocytes derived from newborn rat calvaria, we showed that cAMP levels were elevated 15min after the initiation of streching, and that the protein levels of both IGF-I and osteocalcin were elevated 36h later. Here we report that stretching induces the expression of an immediate early gene, cfos, at 15min and of osteocalcin in several hours in these cells. Furthermore, the blockers of stretch activated channels and epithelial-like sodium channels, in combination, abolish the effects of stretching; elevated expression of osteocalcin and calcium influx into the stretched cells. Independent experiment with a blocker of L type channels also inhibited the osteocalcin expression caused by stretching. Therefore, it is conceivable that the calcium influxes, both primary and secondary, are the essential responses of stretched osteocytes that result in the anabolic reaction of bone.
