201. Identification of a novel bone/calcium metabolism-regulating factor in porcine pancreas.
- Author
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Izbicka E, Yoneda T, Takaoka Y, Horn D, Williams P, and Mundy GR
- Subjects
- Amino Acid Sequence, Animals, Bone Resorption metabolism, Calcitriol pharmacology, Humans, Hypocalcemia metabolism, Isoenzymes antagonists & inhibitors, Isoenzymes genetics, Isoenzymes pharmacology, Molecular Sequence Data, Osteoclasts drug effects, Pancreatic Elastase antagonists & inhibitors, Pancreatic Elastase genetics, Pancreatic Elastase pharmacology, Phenylmethylsulfonyl Fluoride pharmacology, Rats, Recombinant Proteins pharmacology, Sequence Analysis, Sequence Homology, Amino Acid, Swine, Bone and Bones metabolism, Calcium metabolism, Isoenzymes isolation & purification, Pancreas chemistry, Pancreatic Elastase isolation & purification
- Abstract
We purified from porcine pancreas a hypocalcemic peptide clearly distinguishable from other pancreatic osteotropic factors such as amylin, calcitonin, and glucagon. Porcine pancreas was processed by acetone extraction, anion exchange chromatography, isoelectric focusing, and reverse-phase high performance liquid chromatography. Fractions were assayed for their inhibitory effects on bone resorption in vitro. Amino acid sequence of a homogeneous 28-kDa protein revealed 92% homology to a human elastase IIIB in the N terminus. Recombinant human elastase IIIB (rhEIIIB) inhibited bone resorption in organ culture stimulated by 1,25-dihydroxyvitamin D3 at concentrations as low as 75 ng/ml. Antibodies to rhEIIIB recognized purified pancreatic factor in Western blots and blocked its inhibitory effect on bone resorption. This antiresorptive activity was abolished by phenylmethylsulfonyl fluoride, suggesting the importance of elastase proteolytic activity for inhibition of bone resorption. In vivo, rhEIIIB and purified pancreatic factor significantly decreased recombinant human interleukin-1alpha-induced hypercalcemia. In conclusion, a novel naturally occurring inhibitor of bone resorption and calcium-lowering peptide has been identified in porcine pancreas. Because this pancreatic peptide has systemic effects on bone resorption and blood ionized calcium at low concentrations, it may represent a physiological regulator of normal bone remodeling and calcium homeostasis.
- Published
- 1996
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