Preparation of synthetic bovine parathyroid hormone fragment 1-34 for parenteral use in human studies.

There is growing interest in use of synthetic parathyroid hormone peptides such as the aminoterminal 1-34 fragment (PTH 1-34) in human studies, since bovine parathyroid extract is no longer commercially available. We found no data concerning how to sterilize and dilute the synthetic bovine PTH 1-34 (bPTH 1-34) to minimize adsorptive losses and maximize conservation of bioactivity. Therefore, we examined adsorptive losses of electrolytically-labelled, biologically-active bPTH 1-34 onto sterile filtration devices (Millex GV, Millipore Corp.) in solutions of 0.1 M acetic acid containing varying human serum albumin (HSA) concentrations (0.1-5.0%, w/v) and varying hormone concentrations (1-50 micrograms bPTH 1-34/ml). We also assessed preservation of bPTH 1-34 bioactivity (canine renal cortical plasma membranes) in diluted, sterile-filtered solutions refrigerated for 4 days. Adsorptive losses were inversely related to bPTH 1-34 concentrations, being least with 50 micrograms bPTH 1-34/ml, at all concentrations of HSA. Losses during filtration were essentially indistinguishable at HSA concentrations of 0.1 - 1.0%, but were, surprisingly, increased by 2.5 and 5.0% HSA. There were no important differences in adsorptive losses among five different lots of Millex-GV filters. Full bioactivity was preserved over 4 days of refrigeration at a bPTH 1-34 concentration of 20 micrograms/ml. The data suggest that bPTH 1-34 should be sterile-filtered at a concentration of greater than or equal to 20 micrograms/ml in 0.1M acetic acid containing 0.1 - 1.0% HSA. Such sterile solutions are stable at 4 degrees C for at least 4 days.