Effects of synthetic muramyl dipeptide on bone metabolism in the fetal rat

Synthetic N-acetyl-muramyl-L-alanyl-D-isoglutamine (MDP) stimulated the release of 45Ca from fetal rat long bones in culture for 48 h and also increased the number of osteoclasts per bone and the number of nuclei per osteoclast. It also increased calcium uptake in enriched populations of osteoclasts obtained by sequential collagenase digestions of newborn rat calvaria. This effect was observed after a 120 min incubation with 10(-6) M MDP. Effects of MDP on calcium uptake in osteoblasts were not consistently observed. No effects on cyclic AMP were noted in either osteoclast or osteoblast populations treated with MDP for periods from 1-120 min at 37 degrees C.