EXPRESSION OF PROSTAGLANDIN-E RECEPTOR SUBTYPES IN BONE - EXPRESSION OF EP(2) IN BONE-DEVELOPMENT

Prostaglandin (PG) E(2) displays physiological and pharmacological act ion in various tissues including bone, It increases intracellular Ca, and stimulates or inhibits cAMP production through the PGE receptor su btypes EP(1), EP(2), and EP(3), respectively. These receptor subtypes have been recently cloned. In the present study, we investigate the ex pression of these receptor subtypes in bone tissue. RT-PCR revealed th at EP(1), EP(2), and EP(3) were expressed in rat calvariae and that os teoblastic cells (MC3T3-E1) expressed EP(1) and EP(2). In situ hybridi zation analysis using cryosection of neonatal calvariae revealed that EP(2) was expressed by osteoblasts and cells not in contact with bone, probably including preosteoblasts. EP(2) expression was observed at a n early stage in calvarial development, at 14 days prenatal. EP(2) exp ression was also observed at day 3 in rat bone marrow cell culture in which bone-like mineralized nodules are formed at day 8. It has been e stablished that PGE(2) response accompanying cAMP production is one of the characteristics of osteoblasts. The present results indicate that this phenotype appears at an early stage of osteoblastic differentiat ion and bone development.