Effects Of Atrial Natriuretic Factor on Cyclic Nucleotides, Bone Resorption, Collagen and Deoxyribonucleic Acid Synthesis, and Prostaglandin E2Production in Fetal Rat Bone Cultures*

We examined the effects of synthetic human atrial natriuretic factor (human ANF 99-126) on adenylate cyclase activity, cAMP and cyclic GMP (cGMP) levels, bone resorption, collagen and DNA synthesis, and prostaglandin E2 (PGE2) production in fetal rat bone organ cultures. ANF (100 nM) inhibited PTH- and PGE2-stimulated cAMP production but had no effect on basal cAMP production in 21-day fetal rat calvaria. ANF increased cGMP levels, and this was not affected by PTH. ANF (10 nM) partially inhibited bone resorption stimulated by PGE2 but had no effect on control or PTH-stimulated resorption in 19-day fetal rat long bones. ANF had no effect on collagen and DNA synthesis or PGE2 production and did not alter responses to PTH or PGE2 in the fetal rat calvaria. Thus, ANF has no major direct effect on bone resorption or formation, but it is possible that ANF modulates the local regulatory function of PGE2 in bone.