THE NEUROPEPTIDE CALCITONIN-GENE-RELATED PEPTIDE STIMULATES INSULIN-LIKE GROWTH-FACTOR-I PRODUCTION BY PRIMARY FETAL-RAT OSTEOBLASTS

Calcitonin gene-related peptide (CGRP)-immunoreactive sensory nerve te rminals infiltrate all tissues including bone, in which CGRP may play a local regulatory role, To initiate studies on the role of this neuro peptide in bone, osteoblasts were isolated from fetal rat calvariae, t reated with CGRP, and analyzed for cAMP and insulin-like growth factor I (IGF-I) production, CGRP alpha and -beta induced a cAMP accumulatio n in osteoblastic cells, suggesting that they express functional recep tors for CGRP, CGRP induced an increase in both IGF-I transcripts and immunoreactive polypeptide. In contrast to prostaglandin E(2) (PGE(2)) treatment, this increase was not accompanied by an augmentation in IG F binding proteins, Although PGE(2) induced a more significant increas e in IGF-I transcripts than did CGRP, the concentration of IGF-I polyp eptide produced by osteoblasts was similar in response to both treatme nts, It is concluded from this study that CGRP has potent anabolic eff ects on osteoblasts, an observation which opens possibilities to study the potential therapeutic role of CGRP in osteoporosis.