Avian (chicken) parathyroid hormone: synthesis and comparative biological evaluation of the 1-34 fragment

The full-length amino acid sequence of the avian (chicken) form of parathyroid hormone (cPTH) has recently been elucidated. We have chemically synthesized, purified to a high degree, and analytically and biologically characterized the N-terminal 1-34 fragment of the avian hormone. The biological properties of cPTH-(1-34)NH2 were evaluated and compared to the bovine fragment bPTH-(1-34) in several assays. The potency of cPTH-(1-34)NH2 in binding to PTH receptors, in stimulating adenylate cyclase activity and in relaxing smooth muscle tissue was approximately one-tenth that of bPTH-(1-34). Comparison of the avian sequence to other native PTH related sequences suggests that changes in the binding domain of the 1-34 active fragment may account for the decline in potency.