EFFECTS OF C-TERMINAL PARATHYROID HORMONE-RELATED PEPTIDE ON OSTEOBLASTS

A C-terminal analog of parathyroid hormone-related peptide (PTHrP), PT HrP(107-139), was found to stimulate cAMP production in three osteobla st cell preparations. The effect was studied most extensively in ROS 1 7/2.8 cells. The effect was dose-related and comparable in magnitude t o that produced by PTHrP(1-34), but potency was lower. The functional significance of the cAMP effect is unknown, but preliminary findings i ndicated that PTHrP(107-139) also inhibited osteopontin mRNA levels in ROS 17/2.8 cells treated with peptide for 48 h. The results suggest t hat the carboxy-terminal region of PTHrP may play a role in bone metab olism by influencing osteoblast activity.