Islet amyloid polypeptide: production by an osteoblast cell line and possible role as a paracrine regulator of osteoclast function in man.

1. The recently discovered peptide islet amyloid polypeptide shows considerable sequence homology with calcitonin-gene-related peptide, itself an alternative product of the calcitonin gene. The possibility that islet amyloid polypeptide might affect calcium homoeostasis and bone cell function was investigated. 2. Islet amyloid polypeptide messenger RNA was found to be expressed by human HTb 96 osteoblast-like cells in culture, and islet amyloid polypeptide immunoreactivity was present in the cell culture medium. 3. Infusion of islet amyloid polypeptide (150 pmol min-1 kg-1) caused a fall in serum calcium and phosphate concentrations in five patients with Paget's disease of the bone. This was similar to that caused by infusion of calcitonin (50 pmol min-1 kg-1). 4. These findings raise the possibility that islet amyloid polypeptide may act as a local factor within bone, produced by osteoblasts and regulating osteoclast function. The possibility of an action of islet amyloid polypeptide on the renal handling of calcium seems unlikely but is not totally excluded.