In the present study the effect of parathyroid hormone and parathyroid hormone fragments on the intracellular ionized calcium concentration in an osteoblastic cell line (UMR 106-01) is examined. In these cells the intact hormone, bPTH(1-84) and three fragments (bPTH(1-34), hPTH(1-34) and bPTH(3-34)) induce an initial increase of the ionized calcium concentration ([Ca2+](i)). The increase of the [Ca2+](i) due to bPTH(1-84) is more pronounced and of longer duration compared to the increase due to PTH fragments. For two parathyroid hormone fragments with a modified amino acid sequence ([Nle-8,Nle-18,Tyr-34]bPTH(1-34), [Nle-8,Nle-18,Tyr-34]bPTH(3-34)), no effect was found. Our observations suggest: (1) a second messenger role for intracellular ionized calcium in the action of bPTH(1-84)in osteoblasts; (2) a functional role for the COOH-terminal part in the action of bPTH(1-84); and (3) the existence of a specific part of the hormone being responsible for the increase of the intracellular ionized calcium concentration.
|Number of pages||12|
|Journal||Bone and Mineral|
|Publication status||Published - 1988|