Patients with acute pancreatitis commonly manifest hypocalcemia for reasons which are unknown. We found that porcine pancreas extracts (PX) significantly decreased blood-ionized calcium in Balb/c mice. Partially-purified PX with a molecular mass of approximately 27 kDa decreased blood-ionized calcium in the mice. Partially-purified PX suppressed not only 45Ca release from fetal rat long bones which had been stimulated by parathyroid hormone, interleukin-1 alpha, tumor necrosis factor, transforming growth factor-alpha, 1,25-dihydroxyvitamin D3 and prostaglandin E2, but tartrate-resistant acid phosphatase-positive multinucleated cell formation in the presence of 1,25-dihydroxyvitamin D3 in mouse marrow cultures. The results suggest that there is an as yet-unidentified bone metabolism-regulating substance in porcine pancreas which might be responsible for the hypocalcemia associated with acute pancreatitis.