COMPARISON OF THE ABILITIES OF HUMAN PARATHYROID HORMONE(1-31)NH2 ANDHUMAN PARATHYROID HORMONE-RELATED PROTEIN(1-31)NH2 TO STIMULATE FEMORAL TRABECULAR BONE-GROWTH IN OVARIECTOMIZED RATS

N-terminal fragments of PTH and PTHrP, such as hPTH-(1-34) and hPTHrP- (1-34), are sufficiently similar with respect to amino acid sequence, location of functional domains, and higher order configuration to acti vate the same PTH/PTHrP receptor and the same two signal enzymes, aden ylyl cyclase and phospholipase-C beta. Therefore, it was expected that kPTHrP-(1-31)NH2 would stimulate bone growth in ovariectomized rats a s strongly as hPTH-(1-31)NH2. Like hPTH-(1-31)NH2, hPTHrP-(1-31)NH2 st imulated adenyly cyclase in ROS 17/2 osteosarcoma cells as strongly as the standard hPTH-(1-34) and like hPTH-(1-31)NH2, triggered a large d rop in mean blood pressure when injected intravenously. Unlike hPTH-(1 -31)NH2, however, hPTHrP-(1-31)NH2 could not stimulate trabecular grow th in the distal femurs of young, sexually mature, ovariectomized rats .