Synthesis and Biological Activity of Human Calcitonin Analogue.

The potency of salmon calcitonin (sCT) is higher but the structural homology between sCT and human calcition (hCT) is only 50%. Based on the comparison of the structure between sCT and hCT, we have designed and synthesized a hCT analogue (mhCT-2) by solid phase method, using air oxidation in diluted solution to obtain a peptide with intramolecular disulfide bond. Through HPLC purification, we obtained a capillary electrophoresis-homogeneous mhCT, results of analysis of its mass spectrum and N-terminal sequencing were in accordance with the theoretical values. The results of calcitonin bioassay by estimating the blood calcium levels in rats showed that the potency of mhCT-2 was around 2 000 IU/mg, one order of magnitude higher than that of hCT. In RIA assay, we have found that the immunoactivity of mhCT-2 and hCT was much different because of their different binding abilities to anti-hCT antibody. This indicated that the conformation of mhCT-2 was changed as compared with hCT. In rat osteoporosis model, the results showed that pharmacologic effects of mhCT-2 was the same as that of sCT. The synthetic mhCT-2 seems promising to be a clinically useful peptide with high potential in osteoporosis therapy, because it is similar in biological properties to, but less immunogenic than sCT.