Differences in the response to intact b-PTH I-84 and synthetic b-PTH I-34 in isolated perfused bones from young and adult dogs.

Controversy exists over the relative effects of intact b-PTH I-84 and synthetic b-PTH I-34 on the generation of cyclic-AMP (cAMP) by the skeleton. Some experimental models demonstrate that these parathyroid hormone (PTH) peptides are equipotent while other systems show that the synthetic amino-terminal PTH fragment is more potent. The present studies examine the release of cAMP by isolated perfused bone from adult and young dogs in response to intact PTH I-84 and synthetic b-PTH I-34 in order to examine if age is important in determining the response of bone to PTH peptides. The results show that there is a remarkable difference in the release of cAMP between bones from adult and young animals. The release of cAMP in response to synthetic b-PTH I-34 is greater in bones from puppies than in bones from adult dogs. The release of cAMP in response to b-PTH I-84 is minimal in bones from adult dogs which is in agreement with previous studies from our laboratory. In puppies, however, there is a definite response to b-PTH I-84 albeit less than that of synthetic b-PTH I-34.