Stimulation of bone formation by prostaglandin E2

Effects of parathyroid hormone and cortisol on prostaglandin production by neonatal rat calvaria in vitro

We have examined the effects of parathyroid hormone (PTH) and cortisol on the production of prostaglandins, particularly PGE2, by neonatal rat calvaria cultured in a chemically-defined medium. Although there was considerable variability, calvaria produced large amounts of PGE2 in control cultures, reaching medium concentrations of 40 to 200 nM. PGE2 release was partially inhibited by cortisol at 10 nM and markedly inhibited at 100 nM. Bovine 1-34 synthetic PTH produced an increase in PGE2 concentration which was most striking in the presence of a low concentration of cortisol (10 nM). The medium also contained large amounts of 6-keto PGF1 alpha, the metabolite of prostacyclin, which showed similar changes in response to PTH and cortisol. Thromboxane B2 concentrations were low and unaffected by these hormones. 1,25-dihydroxyvitamin D did not increase medium PGE2 concentration. Since PGE2 is a potent stimulator of bone resorption and formation, some of the effects of PTH as well as cortisol may be mediated by their ability to alter PGE2 production in skeletal tissue.